Parasite in Love

The car stopped outside a medical clinic on the outskirts of town. The trip felt like about 15 minutes, but maybe having so much to think about numbed Kousaka's sense of time, and it was really several times longer. Or maybe the opposite, and it was less than half that.

At any rate, they surely hadn't traveled too much of a distance, but in that span of minutes or dozens of minutes, the scenery changed completely. It was white as far as the eye could see.

The area was surrounded by mountains, and the clinic was the only building within view. A sign marking a bus stop stood out on the roadside, and next to it were two pathetically old wood seats. The sign and the seats were covered with thick snow, so a bus driver would be liable to overlook it. Suffice to say, it was a cold place.

The car stopped, and was enveloped with silence. After a breath, Izumi opened the door and got out of the car. Kousaka and Sanagi followed. When their feet touched the ground, there was a crunching feeling of stepping on snow. Only the front entrance had been plowed, so most of the large parking lot had snow piled up high enough for your ankles to sink in.

The clinic was a tidy but melancholy-feeling building. The outer wall was milk white as if intentionally trying to blend in with the snow, so its shape was fuzzy from a distance. The numerous icicles hanging from the roof were over a meter long at longest, and looked ready to fall from their own weight any moment.

On the wall by the entrance was a sign reading "Urizane Clinic." Through the door was a cramped waiting room with three brown sofas in a row. The fluorescent lighting's life seemed almost up, as the room was dim, and the linoleum floors with a slippery glow were an impure greenish color, giving the impression they were growing mold. In the corner was a decorative plant that was so tall, it really didn't mesh with the small room.

There were three patients in the waiting room, all old people. They were talking about something quietly, and looked toward Kousaka and the others when they entered, but quickly returned to their conversation.

A women in her thirties with a face like a Noh mask operated the reception desk. She bowed her head lightly when she saw Izumi, then as if that were the end of that, lowered her head and returned to work.

Izumi stopped outside the examining room, and urged Kousaka to go inside.

"Urizane has something to talk to you about," Izumi informed him. "We'll be out in the waiting room. Come right back once you're done."

Kousaka nodded, then looked to Sanagi. It seemed she was about to look him in the eye, then she averted her gaze and headed to the waiting room, leaving Izumi behind.

Kousaka knocked on the door, and heard a voice inside say "Come in."

He opened the door and entered the examining room. At a desk left from the entrance sat an aging man who looked like a doctor. His short-trimmed hair was pure white, and his eyebrows and thick mustache were similarly so. On his brow was a deep wrinkle like a scar from something. He must be Director Urizane, Kousaka guessed.

Urizane looked up from the desk and turned around. His revolving chair creaked as he moved.

"Take a seat, please."

Kousaka sat down in the patient's seat.

Urizane looked all over Kousaka's body as if appraising him. At the time, Kousaka didn't know that this old man was Sanagi's grandfather, so he didn't think deeply about what those looks meant.

"How much have you heard?", Urizane asked.

Kousaka recalled the conversation in the car. "There's a new kind of parasite in my head, and that "worm" is making me fall in love and become unfit for society. That's it."

"Hmm." Urizane stroked his mustache with a finger. "Well then, where shall I begin?" He leaned back in his chair and sighed. "Kousaka, was it? Just how seriously are you taking this? This nonsense about an unknown parasite in your head, exerting influence even over its human host's decisions."

"...To tell the truth, I'm still only half-believing."

Urizane nodded. "That you would be. It's the perfectly natural response."

"Although," Kousaka appended, "I did hear from Sanagi that certain kinds of parasites can alter people's actions. And so it doesn't seem impossible that there's a parasite that can influence a person's decisions... But to tell me it explains why I've never fit into society sounds so good on paper, it bugs me. I'm hesitant to believe it..."

Urizane interrupted him.

"No, this is not something so good it would bug you. It's so bad it should bug you."

He pointed to a folded sheet of paper. It was a newspaper clipping dated July 20th of last year with the title:

Suicides at Hospital: Doctor and Patient Go Out Together?

"If things proceed like this, you may be walking the same road as them."

Next, Urizane took some documents out of a drawer and handed them to Kousaka.

"Just before the suicides, the doctor mentioned in that article sent me an email. There was no subject or contents, just a single text file attached. The file was a log of all email exchanges between the two from when they met up to their double suicide. Read those, and you should understand most things about the "worm.""

Kousaka looked down and read the first of the documents.

*

Sent: 06/10/2011 Subject: I'm sorry about the other day

It's Izumi. During the examination the other day, I'm sorry for getting incoherent, failing to explain the situation well and confusing you, doctor. I thought I had gotten together everything I needed to say in advance, but when it came time to say it to you, I drew a blank. I can't promise that this definitely won't happen again, so I decided to send an email explaining it. I think this will be more reliable and faster than telling you in person, so...

What I was trying to explain last time were the circumstances by which I came to learn your name, Dr. Kanroji. (I'm sure you thought I was a strange patient for bringing up such an old paper out of the blue. Truly, I'm very sorry.) Thinking about it now, if I'd just explained it chronologically, it would surely be a lot easier to understand. I'm really sorry for being so clumsy... I'll learn from my mistake and try to properly tell you the events in the order they happened. It will be a little long, so please forgive me.

At first, I had the symptoms of a headache. I remember it to be in the middle of April.

The headache lasted nearly half a month. I've always had migraines, but the pain had not been this long-lasting before. Previously, I could take medicine and it would heal in two or three days.

That said, I did not consider it very serious at the time. I thought it may be the result of stress, or hay fever acting up. In truth, the headache itself was not such a big deal. After half a month, the pain began to lessen, until finally it went away completely. I was relieved that it was a temporary affliction after all.

The problems came after that. A while after my headache was cured, I realized I was having strange delusions.

I work as a temporary employee at town hall, and normally commute there by driving. One day, I was headed to work as usual, but after passing through a normal intersection, I was suddenly struck with an incredible sense of terror. I quickly hit the brakes, parked on the side of the road, and looked behind myself.

A possibility crossed my mind: "Might I have just run someone over?" Of course, if that had really happened, there would have been a strong impact to the car. No matter how much I was spacing out, I would have known that clearly. Yet I couldn't help but get out of the car and check. Naturally, there was no damage to the car, and there was no person collapsed and bloody on the road I'd driven past. But still, that thick terror persisted in me.

Starting then, whenever I was doing anything, I would be tormented by the fear that I had unconsciously caused harm to someone else. For instance, while going down stairs at a train station, I would become anxious that I unknowingly pushed someone down them. When working, I would be anxious that I had made some massive error and caused everyone trouble. While shopping, I would be anxious that I was unknowingly shoplifting. After meeting someone, I would be anxious I had said something that hurt them. It was fine when it was something that I could check then and there, but in the case of "what if I ran someone over," I couldn't relax until I'd seen the newspaper the next day. It was like that headache that lasted half a month had driven me mad.

I gradually came to find leaving the house troublesome. Scared of harming them, I kept people distant, and became a loner. I could feel peaceful only when I was all by myself at home, sitting still.

I was aware that it was a type of obsessive-compulsive disorder called blaptophobia. And I did have the knowledge that obsessive-compulsive disorders have little hope of being cured naturally. ...Regardless, I was strongly opposed to seeing a psychiatrist. Perhaps I didn't want to admit I was mentally ill. Until then, I had thought of myself as a strong woman.

However, I couldn't stay like that forever. My blaptophobia worsened by the day, and it began to interfere with normal life. So I decided to make up the story "I'm afflicted with chronic headaches, and it's caused me to become overly nervous" to create a reason to go to the hospital, first having a general physician look at me. If they recommended me a psychiatrist, then I intended to obediently go along with that.

However, my test results revealed an unexpected truth. It appeared my blaptophobia was highly likely to be not purely a mental illness, but resulting from an organic alteration in my brain. Unbelievable, there was a parasite in my brain, and that worm was creating a focus infection on it.

I was relieved. It sounds strange that I was relieved to learn there was a parasite in my brain, but I think I was pleased with how easy it was to understand. Thinking that simply removing the parasite could free me from my irrational fears, my heart was cleared up at once.

However - and this is where the story gets increasingly strange - once it came time to undergo treatment, I was hit with an unidentifiable anxiety. It differed in nature from the delusions of hurting others I'd been having; it was a completely baseless feeling that came down upon me. I don't know why, but I had a sudden premonition that if I went through with this treatment and expelled the parasite, I would regret it.

I provided a suitable excuse and fled the hospital. And I never went back there again. What's wrong with you?, I thought to my own self. Yet strangely, I didn't feel like I had done the wrong thing. I think my head was filled with relief from escaping the terror that stood before me.

However, a month afterward, my doubts began to swell. What indeed was the cause of that unidentifiable anxiety? Why had I done such a thing, volunteering my body to protect a parasite? I had been optimistic, thinking that later I could sort out my feelings and the reason would become clear, but the reality was that the mystery deepened by the day. It was as if at that time, I was no longer myself...

Suddenly, I recalled an article I read in a magazine about a year prior. It stated that certain types of parasitic organisms could have effects on humans' personalities and actions.

I searched my memories and dug up that article, and read it over and over again. And after reading related articles and citations, I arrived at the "next" conclusion, so to speak.

My brain was already under the parasite's control.

People may laugh it off as a foolish delusion. In fact, it is the mad idea of a sick person. It's not all that different from a patient with schizophrenia thinking they're being attacked and controlled by radio waves. If my brain has already been eaten into by a parasite, then perhaps I can no longer think properly, I considered. However, that there really was a parasite in my brain was not a delusion, but a proven fact. I figured that I could doubt my brain only after I had learned the truth about this parasite.

I looked into the author of a paper that was of particular interest to me. And I learned that this author worked at a university hospital not far from my parents' house. I couldn't help but feel a kind of destiny from that. And that was what led me to you, Dr. Kanroji.

Sent: 06/11/2011 Subject: Re: I'm sorry about the other day

This is Kanroji. I've read your email. That certainly explains why you suddenly started talking about a paper. Thank you for your detailed explanation. I have a much better idea of the situation now.

Now, let me be honest, I am very surprised. But to explain my surprise, I believe I'll have to tell a rather long story of my own.

I ask that you keep everything written below a secret.

It happened half a year ago. Two patients suspecting a parasitic infection came to visit me. We'll call the man Y, and the woman S.

Y and S were a married couple over twenty years apart. In addition, it was the husband Y who was the younger one, unusually. They were an extremely intimate couple, and while it had been half a year since they married, they had a charming air about them like lovers who just started dating.

The two reported having chronic headaches, and an MRI brain scan showed cysts in several places. Strongly suspecting a brain parasite infection, I extracted cerebrospinal fluid from both for a definite diagnosis, and discovered several parasites about a millimeter long.

Up to that point, things seemed fine.

When I looked at them under a microscope, I doubted my eyes. The appearance of the parasites taken from their cerebrospinal fluid didn't resemble any parasite I'd ever laid eyes on. They were shaped like teardrops, with two suckers around the pointed end. There was a pair that appeared to be mid-copulation, two bodies adhered together in a Y shape. Based on characteristics of form, it didn't seem likely they were trematodes, but I didn't know anything beyond that. After several days of research, I concluded that the parasites extracted from the couple were a new species.

Considering the brain could be the target of infection, I took caution in treating them. The worms, which infected the central nervous system, could not be excised recklessly. There were cases where cysts would fossilize and remove the need for treatment, and sometimes the inflammation reaction that resulted from treatment could be worse than the disease itself.

However, it was also not a situation where I could hesitate. According to Y and S, a while after the headaches began, they experienced strange changes in their mental state.

Both of them said they couldn't help but be bothered by the smell of others. This hadn't been the case before, and they claimed to have had fairly dull senses of smell, but as their headaches receded, they became disgusted by other people's body odor. It wasn't the smell of sweat or the smell of perfume; even smells so normal they wouldn't even be called smells felt so unpleasant, they felt agonized interacting with others.

The couple was certainly uneasy, and asked me if there was a connection between the parasites and these symptoms. Personally, I could only answer that I didn't know at the current time. An external head wound could damage the olfactory nervous system that linked the smell receptors and the brain, and a brain degenerative disease could damage the olfactory nerves themselves, causing the loss of smell. However, a case like theirs where the sense of smell became oversensitive was not often seen. It was a possibility that an infection in the paranasal sinuses or mouth caused smell abnormalities, making ordinary smells displeasing, but... considering the point that both of them displayed the same symptoms, it felt better to suspect that their hyperosmia was psychogenic in nature. At the same time, I hadn't forgotten that compulsive disorders could result from the onset and progression of organic brain diseases.

However... To tell the truth, I didn't pay much heed to their mental illness itself at first. Perhaps it was a kind of folie à deux - at any rate, I thought it best to prioritize removal of the parasites. I supposed that as long as the cause was cut off, the mental symptoms would also be eased.

Yet, when I was about to enact treatment, Y and S stopped showing up at the hospital. I tried calling them, but they refused to come to the hospital for seemingly on-the-spot reasons like being busy with work or not feeling well. And it didn't happen just once or twice. To my eyes, their behavior seemed protective of the parasites. What they were thinking, I had not the faintest idea. Surely if you heard there was a parasite in your brain, you would normally want to have it removed no matter what.

And then you appeared, Izumi. There were many similarities between your symptoms and theirs. A minor headache, an escape from interacting with others, a denial of treatment. I examined you thinking it couldn't be so, but I found your test results were nearly the same as Y and S's. It isn't as if I've confirmed the worm itself, but I don't doubt the parasites in your skull are the same as the ones in theirs. And I'm considering that, as aforementioned, those parasites may have caused your mental disorder.

Of course, I can't draw a definite conclusion at the moment. After all, this parasite has only infected a mere three people. No general approaches can lead us anywhere from there. We could even consider it all a coincidence. But I don't believe this is a simple trick of fate. My sixth sense is telling me I'm only looking at the tip of some massive secret.

Sent: 06/11/2011 Subject: Thank you very much!

It's Izumi. Thank you for your quick reply. I was thinking that nine out of ten people would ignore it as the ramblings of a madwoman, so I didn't expect such a detailed response! I'm very glad.

I also can't help feeling that there is some kind of connection between Y and S's mental symptoms and my own. Of course, I haven't even seen the two of them in person, so my hunch may be more wishful thinking than a sixth sense...

But if you say so, Dr. Kanroji, I think it must be true. I trust your judgement.

I'll visit the hospital on June 14th. I hope I can speak without being nervous this time.

Sent: 06/20/2011 Subject: About a fourth patient

This is Kanroji. There's been a new development regarding the new species of parasite, so I'm letting you know. As per usual, please keep the contents of this email secret.

The other day, I identified a fourth person who was infected. A woman named H, the youngest of them all thus far. Like previous patients, H came to the hospital citing chronic headaches, rejected treatment of her parasitic infection, and showed a strong trend of avoiding relations with other people. Examination of her brain also showed a cyst-based focus, and by further comparisons, I came to the decision that it was brought about by the same parasite. Also, in H's case, her drift away from other people materialized in the form of scopophobia. It does seem there are personal differences from patient ot patient in how the symptoms manifest. At any rate, there is little room to doubt that the worm is the cause of these mental illnesses.

What I can't understand is why four patients with a never-before recorded parasitic disease have come to me in rapid succession. To my knowledge, the same parasite has not been extracted from any patients at any other hospitals. Also, the four patients I've examined do not have any history of traveling abroad, and live in various regions, and I could find no common points to speak of. As a result, I'm currently unable to grab even a clue about how these patients came to be infected by the parasite. Perhaps this worm was just brought to this country from abroad by some means, and is in the process of expanding its range.

Relevant to this fourth patient, I'd like to answer a question you asked me during your examination on the 14th. To jump to the conclusion, it is as you feared. I am conducting experiments with the new parasite using my own body. I've done this not just for the treatment of the patients, but out of curiosity as a scientist. Thus, to be specific, H is actually the fifth case of infection.

It hasn't been many days since the infection, so there have been no symptoms that could be called symptoms yet, but the worm is gradually multiplying inside my body. If my expectations are correct, I will eventually exhibit a mental disorder like yours. Also, in the process of treating Y and S, I have found that no surgery is necessary to remove the parasites; application of albendazole and corticosteroids is effective, as with other brain parasitic diseases. As such, you may rest easy knowing there is no chance of it turning severe. It would be a waste for the doctor to collapse, after all.

Still, how is it you knew then that I was infected with the parasite? When you asked, it appeared to me that you were convinced I had the worm in my body. Was there some kind of external change you could observe? If possible, could you tell me the reason?

Sent: 06/21/2011 Subject: Re: About a fourth patient

It's Izumi. I'm relieved to know there's no worry of anything serious. Still, I see you really are passionate about research. I take off my hat to you. That said, please be kind to yourself, and don't push too far.

How could I tell the worm was in your body? To tell the truth, I don't know. The moment I saw you that day, it simply occurred to me. "Ah, the doctor's become the same as me."

Perhaps I did subconsciously notice minuscule changes in your expression and actions, and that conclusion was the only way I could explain that nagging sense of wrongness. But I really don't know the truth. I think it really was something that just wormed its way into my head.

Now, this will seem sudden, but I want to talk to you about something. Even I have to say it's something rather abnormal, so please take it with a grain of salt, and consider it the nonsense of a mad patient.

Lately, I've been thinking about you for the entire day. When I wake up in the morning, before I put on makeup, when I dry my hair, during work, not a moment goes by without it. What day we'll meet next, what clothes I should wear, what I should talk about, what I should do to let you know more about me... It's all I think about.

You may be somewhat aware of it too, but it seems I'm in love with you. I'm conscious of the fact that it's likely a kind of positive transference. And I'm deeply aware that revealing this fact to you will only cause you worry. But as much logic as I apply, it's not easy to feel satisfied by it.

It may be that this will lead me to cause you immense trouble in the future. So I will apologize in advance. I'm terribly sorry. And please, don't abandon me.

Sent: 06/24/2011 Subject: Progress report

This is Kanroji. I'll give a brief report about the change in my mental state caused after infection.

The first change was that seeing patients became agonizing. At first I considered it to be work fatigue, but before long, it extended from "patients" to "any other people." This symptom matches the "escape from interactions with others" that the four have in common. Though the manifestation varies - in Y and S's case, "being made uncomfortable by other people's smell," in your case "fearing causing harm to other people," and in H's case "bothered by other people watching"... I consider them all the same at their root.

This is my theory: In essence, those infected with the worm become misanthropic. I'm hypothesizing that the differences in exact symptoms between the four are a difference in what each of them traces this baseless misanthropy forced upon them by the worm back to.

Of course, I am unsure what merit there is to the worm depriving its hosts of socialization. ...To provide an example, certain kinds of tapeworm will cause small crustaceans known as Artemia, which normally act independently, to act in a group. Because by doing this, they can increase the odds of the Artemia being eaten by their final host, the greater flamingo. So I could understand bringing hosts together to such an end. However, what meaning could there be to the worm isolating its host?

That we are finding adult worms in our bodies means that humans are the worm's final hosts. The final host's role should be to spread eggs and larvae, so it's clearly not logical to isolate the human. Perhaps there is some deeper goal that we cannot imagine.

The second change, you can probably guess. I have some slight resistance to expelling the parasites from my body. But I will omit further explanation. Cases of the host becoming almost attached to parasites that should be harmful to it are not unusual enough to be worth mentioning.

The problem is in the third change. This relates to the "nonsense" you wrote about in your previous email.

Truth be told, I was very glad to read your confession. No, not exactly - and I know as a doctor, this is improper - I think I may have an even greater affection toward you than you toward me. Regardless of the definite progression of misanthropic symptoms, those thoughts only grow stronger by the day.

However, we must not jump to conclusions. Before any premature celebration, there is a matter we must first consider.

When putting the worm in my body, there was something I had decided in my heart. Namely: I would examine every psychological change that followed with suspicion. Once under the worm's influence, I can no longer be certain how much is my own will and how much is not. Which means I can only suspect everything.

As such, I question these feelings of romance. And I am not just doubting them at random. I have an idea.

In observing Y and S, I have witnessed a deeply intriguing change. Treatment has progressed, the effects of the worm weaken, and their misanthropy is certainly improving, but as if contrary to that, I notice their hearts growing apart. Two months after their treatment began, that sense of newlywed intimacy I felt when I first met them seems to have gone without a trace.

At first, I explained it as a result of the anxieties about this unidentified disease putting them in a state like "falling off a suspension bridge." That with the urgent danger gone, they had run out of material to fire up their love. But having now personally experienced infection by the worm, I can't help but feel some deeper meaning to the change in their relationship. As if, for instance... their love was something that was being maintained by the worm.

Izumi, what I want to tell you is more or less this: As long as there is the possibility that the worm influences even its host's romantic feelings, we should not easily draw conclusions about our feelings.

I hope you can make a calm judgement.

Sent: 06/25/2011 Subject: A few questions

In other words, you're trying to say that we're not in love, but that the worms in our bodies are in love?

I'm sure a layperson like myself couldn't understand... but let's say there is a worm that has the power to make hosts fall in love with each other. Why does it need to have such an ability? Even if that is one of the worm's strategies for propagation, why would it make infected hosts fall in love with each other?

It would be understandable if the infected were made to fall in love with someone healthy, increasing the chances of infection. But what reason could there possibly be for bringing together only those who have already been infected?

Doctor, are you trying to tell some plausible-sounding lie to keep me away and avoid hurting me? I can't help but suspect that's what it is.

Sent: 06/28/2011 Subject: Re: A few questions

Your doubts are understandable, Izumi. I have been plagued with the same doubts these past few days. How would making two hosts in which the worm has already established itself fall in love prove advantageous for propagation?

I had a flash of insight into a possible answer to that question just yesterday, while walking down the avenue. (I often take such aimless strolls when I'm thinking.) I wracked my brains and couldn't find a good explanation, so while looking at Yoshino trees on the roadside, I thought on it.

When I was a small child, one of my friends was an oddball who got poor grades in elementary school, yet had high-school-level knowledge of biology. One day, I was walking with that friend to school under cherry trees, and with a sudden thought, he asked me a question. "Have you ever seen Yoshino trees with fruit?" f𝔯𝒆𝚎𝚠𝑒𝚋𝓃૦νℯƖ.co𝘮

I told him that thinking about it, I don't think I ever had, and he proudly told me about how it worked.

"That's because Yoshino trees have strong self-incompatibility - a genetic characteristic that prevents self-pollination. In human terms, it's like a system that prevents inbreeding. Yoshino trees are clones artificially multiplied using grafting and stuff, so however they pair up, any cross-fertilization is always going to be inbreeding. So while a half-breed can be born from cross-pollination with another type of cherry tree, there can't be a kid from two Yoshino trees. And since Yoshino trees aren't often grown with other cherry trees, that's why they have hardly any chances to bear fruit..."

At that point in my recollection, it came to me.

What if the worm worked the same way as Yoshino trees?

What if the worm also possessed a system that prevented breeding between those with the same or similar genetics by recognizing blood relation?

I pursued that thought further. What if that non-self discrimination system was "forbidding reproduction of those who matured in the same host"? In order to reproduce with one who matured in a different host, it would be necessary to come and go between hosts. (Insect-pollinated flowers can't ask pollinators to take just the pollen, after all.) And to fulfill that objective, would it not be perfectly reasonable to suggest a strategy of making hosts fall in love?

It was an outrageous idea, to say the least. Due to a lack of basis, I am making some leaps of logic. And it does sound like the idea of someone who's read too much science fiction. I tried to laugh off this unrealistic idea. Indeed, it's not only plants and fungi; some animals also possess such a system of self-sterility. Ciona intestinalis, for instance. But even for the sake of genetic diversity, there could not possibly be a creature with such a complex, roundabout method of reproduction...

That's when I stopped in my tracks. I realized that there did in fact exist a creature that, regardless of being capable of parthenogenesis, took a "complex, roundabout method of reproduction." ...Yes, it goes without saying. I refer to the parasite you brought up in an earlier conversation: Diplozoon paradoxum.

It isn't restricted to D. paradoxum. For example, some kinds of liver fluke are hermaphroditic and capable of parthenogenesis, yet cannot mature into adults without two coming into contact. When you really think about it, this seemingly illogical and complex reproductive strategy is actually very commonplace in the world of parasites.

I am trying to investigate this idea further. If there truly exists a parasite that makes pairs of infected hosts fall in love, how might the infected recognize other infected? Surely, they must be sending some form of signal. I don't know what nature it has or its intensity, but... at any rate, I theorize the existence this signal is the reason for the implausible outcome of all these infected patients flocking to me one after another. Perhaps those infected by the worm are unconsciously brought together.

With this theory, the illogical-seeming strategy of making the host misanthropic also gains a possible explanation. For instance... what the intent of the worm's control is not isolation of the host, but bringing fellow hosts together? If all the members of a given group are infected by the worm, that group's exclusiveness and cohesiveness can be expected to skyrocket. In such an infected group made to have mutual cooperation, the capacity for continuation is higher than a non-infected group, and thus the chance of each member surviving would also be high. That would be an extremely desirable thing for a worm which makes humans its final residence.

Parasites having an effect on the host's sociability is something that has been pointed out long before. Even Dawkins pointed out that the highly-advanced social structures of termites were brought about by the control of microorganisms in their bodies. By mouth-to-mouth feeding, termites spread the microorganisms to the entire group, and it's thought that this action is induced by the microorganisms for reproduction. For a more extreme example, there even exists a theory stating that the social nature of vervet monkeys and Japanese monkeys, and consequently humans, was caused by a retrovirus. If viruses and bacteria can do so, then perhaps there's nothing strange about the worm being able to influence human society.

I have no such feelings of wanting to keep you away, Izumi. In fact, it's because I want to love you with such conviction that I am desperate to expel any shred of doubt.

Thinking about it, in these near fifty years of life, I have always been alone. Whoever I was faced with, my feelings were never shaken, and the more I got involved with people, the more hollow it felt. So soon after turning forty, I entered a kind of unfeeling state, passing the days and living though I felt like I was dying. But meeting you has brought back a trembling in my heart I haven't felt in a long time. When I talk to you in person, my heart aches like a young boy just learning love. And that is why I have misgivings. If these feelings were merely brought about by that worm, nothing could make a bigger mockery of humanity.

Sent: 06/30/2011 Subject: (no subject)

I'm happy you said that, doctor.

I'm very, very happy.

Enough that I would be fine just dying.

But if your theory is correct, then if the worm were gone, I would lose these feelings too.

I've come to think of that as a very sad thing.

I'll come to the hospital at the start of July.

So long.

*

The correspondence between the two ended there. Kousaka was silent for a while, still staring down at the documents.

He looked over the dates on the article and the emails again. Their email correspondence ended on June 30th, and by July 20th, the two committed suicide. Only God knew now what happened to them in that twenty-day period. They hadn't told anyone the most important part, taking that secret to their graves.

There was no question of Urizane's intent in showing him these. Kanroji and Izumi fell in love due to the worm's influence, and afterward, carried out a mysterious double suicide - so then it was highly likely that Kousaka and Sanagi who also fell in love due to the worm's influence would repeat the same thing.

That must have been it, more or less.

Kousaka returned the newspaper clipping and documents to Urizane. And he asked.

"Is the "H" mentioned here referring to Sanagi?"

"Yes, you're correct," Urizane affirmed.

Kousaka pondered for a few seconds, then asked another question. "Was Sanagi's personality different before she was infected with the worm?"

"That's a tough question." Urizane's mouth made a slight frown, and he scratched the back of his neck. "In a way, you're right, but... Things are a bit too tangled to say for sure."

"Which is to say....?"

Urizane shifted his body slightly to look out the window. The chair squeaked as he moved. The upper part of the view from the window was obscured by a long icicle hanging from the roof.

"I'll explain things in order, that included. The things that have happened to Hijiri in the past year. And the way in which the worm has ruined her life."

Urizane put his hands on his knees and sat straight.

Urizane began: It started with the suicides of a certain couple.

They were on good terms, they had no economic trouble, the husband's job went well, the wife was pleased with being a housewife, and their only daughter was growing up well. It was the very picture of a happy family. There was not a single reason for them to take their lives.

Yet there was no room for doubt in the fact that their deaths were suicides. The two of them holding hands as they lept off a bridge in the mountains had been witnessed by people walking by. ...That was about a year ago.

Only their daughter remained. Hijiri. She had only just turned sixteen, and had no other relatives, so she was put in the care of her grandfather on her mother's side - that is, myself.

For some time after I took custody of her, she hardly talked to me. It appeared not that she was refusing to talk, but that she had forgotten how to speak with others. She used to be a cheerful girl with many friends, but like a changed person, she became quiet, using as few words as possible even at a school. I thought then that it was from the great shock of her parents' deaths. Her late mother - though I hadn't heard for her in a long time - was my daughter after all, and I had been bereaved of my wife just two years prior, so I perfectly understood Hijiri's sadness.

However, the truth differed from my expectations. She was not merely saddled with grief.

She was thinking to herself the whole time.

Eventually, Hijiri said something with no prior warning.

"I don't think it was a suicide with mom and dad."

"What do you mean?," I asked. And Hijiri began to speak like letting a dam burst. About how her parents began acting strange about half a year prior to the suicides. They came to abnormally fear other people, and demonstrated illogical persecution complexes - "the neighbors are watching me," and "I'm always being followed."

"I found it strange how they suddenly got like that, but now, I finally feel like I understand the reason," she told me. "The two of them were sick. And it seems I've caught the same sickness."

I couldn't understand even half of what Hijiri was saying. However, when she not long after started to frequently skip school, and became distant with me, I finally understood what she meant by "sick."

She's walking down the same path as her parents, I felt innately. I could see that if left alone, she could reach a point there was no returning from. It did not seem like something that could be left to natural healing.

I took Hijiri to various psychotherapists and psychiatrists. But there were no important findings; all that became clear was that she had a fear of being watched by others, and there were no signs of improvement.

A breakthrough came from the words of a certain clinical psychologist. While explaining to me how the treatment was going, the young woman said, "That reminds me..."

"In the middle of an ordinary conversation, Hijiri said this to me. "There's a worm in my head." She didn't seem to expect much reaction from me, but it struck me. I thought it might be a lead to understanding her mind, so I asked her to explain in more detail. But she said it was a joke and dodged the question, and hasn't brought up the topic of a worm since."

Afterward, the clinical psychologist explained the common psychological interpretation of "a worm in my head." In rare instances, immense stress or dissociative disorders could cause such delusions of parasites.

However, I felt myself strangely hung up on the words "a worm in my head." Even when I slept, even when I woke, the words wouldn't leave my mind. I couldn't help but suspect a special meaning in her casual remark. I suppose it came from not perceiving things as a doctor, but an instinctive sense as her grandfather by blood.

Lately, it did seem she was having chronic headaches, and was consistently using painkillers. I had considered it a common thing for a girl her age, but once I began to suspect, I couldn't rest without confirming the cause.

I resolutely asked her myself, but Hijiri would not back down on the point of "I didn't say anything like that." So I fabricated a reason to draw blood from her, and went to have it tested.

I gulped when I got back her results. There was an increase in eosinophils and high IgE levels, characteristics found in allergic reactions and parasitic infections. Of course, I couldn't conclude from that alone that there truly was a "worm in her head," but it was clear at any rate that some change was occurring in her body.

I had a friend assist me in meeting a medical professor who specialized in the field of parasitology. That professor was Yutaka Kanroji - the man who became the center of this incident.

He was around his late forties, and had a moody scientific look, but was also quite tall with striking facial features. He was a charming man. He seemed famous in the area, known to be so passionate about parasitology that he wouldn't hesitate to infect himself with a parasite for the sake of research.

I spoke to Professor Kanroji. About the illogical death of the couple, the abnormalities in my granddaughter, her chronic headaches, the "worm in her head," and the blood results. I was prepared to be laughed off, but Professor Kanroji showed unparalleled interest. Above all, he seemed to have a sharp reaction to mention of the "worm in her head" and scopophobia.

Hijiri was made to take several special tests. The next week, I tried to take Hijiri with me to hear the results, but she denied, using her headaches as an excuse. I could see it was only temporary, but not wanting to force her to come if she didn't want to, I went to Professor Kanroji's hospital alone.

There, I was informed of the shocking truth.

"First, take a look at this."

Professor Kanroji showed me an MRI of Hijiri's brain. There, I could see multiple ring-shaped areas of contrast. Next, he showed me the blood results. Before I could look over the numbers, Professor Kanroji readily informed me.

"To jump to the conclusion, there is a parasite in your granddaughter's head."

I gasped, and slowly nodded. Some way or another, I was able to accept the truth with such calmness, even I found it odd.

Professor Kanroji continued. "However, in a sense, we could call your granddaughter extremely lucky. Of course, there's no question that the parasitic infection itself is unlucky... but it is nothing short of a miracle that you first came to me to have her examined."

Then he explained to me how he had other patients with similar symptoms to Hijiri. How they had a new species of parasite in their heads, how it was possible the "worms" might be manipulating their hosts' minds, but how it was perfectly curable with existing treatments.

The next day, I visited his hospital again with Hijiri. And Hijiri began treatment under Professor Kanroji. Such was how we came to be involved with the professor - but not a month later, we heard about his passing.

Professor Kanroji's suicide was all over the news. A medical professor committing suicide at a university institution was a story in itself, but the fact it was not just a suicide, but a double suicide with one of his patients, caused a major clamor. All manner of theories went around.

I showed Hijiri the newspaper article about Professor Kanroji's death. I knew there was no point in hiding it. She looked over the article, and said to herself, "Huh, like my mom and dad." That was the very same impression I had gotten.

"That doctor probably used his own body as a test subject for the parasite," Hijiri said with an unchanged expression. "And he was such a good person..."

"You see that parasite as the cause of his suicide too?", I asked, and she nodded as if it were obvious.

"The patient he committed suicide with was probably one of the infected patients. The woman who came to Professor Kanroji just before me."

I thought about it, then asked Hijiri this.

"I'll ask you honestly. Do you feel even the slightest desire to die right now?"

"I guess I'd be lying to say there wasn't any," Hijiri shrugged. "But that's been there for a long time. It didn't just start now. Enough to explain it as a gloomy personality."

I was relieved to hear that.

"Suppose this parasite is a dangerous creature that can cause the infected to commit suicide," she said, poking her forehead. "Maybe those symptoms can differ between people? If they didn't, the couple who first came to the hospital should have killed themselves a while ago."

"Aren't you scared?" I couldn't help but ask, perhaps from seeing my granddaughter accept the situation so calmly.

"I'm scared. But at least one more thing is clear now. Mom and dad didn't kill themselves and abandon me. The parasite just killed them."

With that, Hijiri smiled. Ironically, that was the first smile she'd shown me since coming into my custody.

I only noticed that evening that Professor Kanroji had sent me an email just before his suicide.

Maybe Professor Kanroji was worried up to the very end that he'd take his life and abandon his three patients. That's why he entrusted it to me, who worked in the same business, and as the relative of a patient, knew much about the circumstances around the worm. He probably sent me their emails as-is due to not having time to leave a concrete message.

I read over the emails between the two again and again, but still knew nothing about the mechanism that caused the worm to induce the death of its host. What was clear was that even an intellectual like Professor Kanroji couldn't resist the worm.

I carried on the treatment of Yuuji Hasegawa and Satoko Hasegawa - the "Y" and "S" mentioned in the emails. Parasitic disorders were not my specialty, but following the treatment in the emails, I continued the deworming of the Hasegawas and Hijiri.

Considering the four who had died so far were all couples of infected, I advised the Hasegawas to spend time apart for now. They readily took my advice. They even seemed relieved to have a justification for living apart. So it was just as Professor Kanroji said in his email. It seemed their relationship had been ruined beyond repair.

While the Hasegawas were recovering, Hijiri's symptoms meanwhile showed absolutely no sign of improvement. She should have been taking the same anthelmintics, but there was a striking difference in their effectiveness. The Hasegawas' misanthropy gradually lessened, but Hijiri's would not improve, only worsen.

That made sense, as it turned out. Because Hijiri wasn't taking the anthelmintics.

One day, I happened to witness it. I was present when Hijiri threw the medicine into the trash without taking it. Hijiri met eyes with me, and didn't apologize; she just shrugged, as if to say "you can get mad if you want to."

That one time, I reprimanded Hijiri. I asked her if she knew what she was doing, and she sighed with a fed-up look. And she muttered this.

"I don't need to be cured. I don't care if it kills me. I want to say goodbye to this world quickly."

That's because of the worm in your body, that's what it's making you think to protect itself - as much as I tried to tell her, it had no effect. Soon, she dyed her hair bright, and got her ears pierced. She skipped school, and read nothing but old philosophy books and writings about parasites.

It seemed that to expel the worm in Hijiri's body, it would be necessary to cultivate a desire to be cured. However, I had no idea how to give her a positive attitude about deworming.

That was when Mr. Izumi appeared. The surname of this man who came to me out of the blue without any appointment sounded familiar. And of course it would. He was the father of Ms. Izumi, the woman who committed suicide with Professor Kanroji. He had also received an email from Professor Kanroji, and was aware of the existence of the worm.

He was a bodyguard, currently working for a major defense corporation, but my first impression of him was that rather than a bodyguard, he was more of a scientist or engineer. His way of speaking had that kind of logic. Mr. Izumi did not despise the insolent doctor who had carried out a double suicide with his patient. In fact, he respected Professor Kanroji as a brave doctor who was trying to cure his daughter, at the ultimate cost of his own life.

I found it strange that he could be so calm. If it were not his daughter but my granddaughter who had killed herself with Professor Kanroji, could I respond so gracefully? No, I believe that would be impossible.

Mr. Izumi came to me asking whether there was anything he could do to help exterminate the worm. At first, I politely declined. I appreciated the offer, but honestly was doubtful a layman like him could provide any help.

He clung on, however. Please, let me help somehow, he begged. I saw an unusual light in his eyes. I made a guess: Perhaps this Mr. Izumi wants his daughter's death to have some meaning. For his daughter's death to serve as an impetus to move him, and that leading to the salvation of other patients - was that the kind of development he sought? Perhaps I was just barely capable of giving him something of the sort.

I deeply sympathized with him, and gave his request further examination. And I came upon a job that he could be tasked with.

When I told him that Hijiri was pessimistic about treatment and had a weak will to live, he jumped on it.

"Leave that to me." He thumped his chest. "I'll definitely get your granddaughter to open her heart."

And so Mr. Izumi began his efforts to bring back Hijiri's will to live. And before long, he found you. It was a complete coincidence. Mr. Izumi was merely looking for people who might form a close relationship with Hijiri, and did not imagine he would happen to find another person infected by the worm.

In any event, this resulted in you and Hijiri falling for each other, and her opening her shut-off heart. If I hadn't heard out Mr. Izumi's request out of sympathy, Hijiri would likely still be alone and holding the darkness in her heart to herself. I suppose this is why they say: the good you do for others is good you do yourself.

*

The story ended there. Urizane held his throat and cleared it. He must have been tired from talking.

Kousaka tried to mentally sort out the contents of the emails he read and Urizane's story. The three broad points that were clear about the "worm" in his body - and in Sanagi's - were as follows.

1. The worm isolates its host.

2. The worm makes hosts fall for each other.

3. When certain conditions come together, the worm's hosts kill themselves.

"In short," Kousaka spoke, "you've called me here to kill the worms before Sanagi and I meet the same fate as Professor Kanroji and Ms. Izumi?"

"That's correct."

"Which means..." Kousaka thought. "You're going to pull Sanagi and I apart?"

"Precisely. It was none other than ourselves who brought you together, but the situation has changed. The reason Mr. Izumi hired you to be Hijiri's friend was in hopes of opening her heart and regaining her will to live. His judgement was not wrong, but... if that was the worm's doing, then that's a different story. I'm very sorry, but I can't let you be with Hijiri any longer. In case the unthinkable happens."

Kousaka tried imagining the "unthinkable" Urizane spoke of. The instant picture of him and Sanagi committing suicide together resounded surprisingly well in his heart. I see - as we are now, it wouldn't be too strange for things to end up that way, Kousaka thought, as if he weren't even part of the equation. If Sanagi asked him to do it, Kousaka probably wouldn't refuse, and if Kousaka asked her to do it, Sanagi probably wouldn't refuse either. "It's hard to live" sufficed as a reason.

Maybe it was only a matter of time before Kousaka arrived at that idea, and it just hadn't happened yet. Perhaps as soon as tomorrow, he could have arrived at the idea of a double suicide on his own, and suggested it to Sanagi. Thinking it gave him a chill.

As Kousaka pondered silently with folded arms, Urizane spoke.

"I won't ask you to reply right away. I assume you need time to sort out this sudden influx of information?"

Kousaka nodded.

"I'll send for you in five days. Please decide whether you'll undergo treatment or not before then. The treatment itself is simple, so no real preparations are necessary, and we can begin as soon as you have an answer."

Kousaka recalled how Kanroji's emails had mentioned that the treatment didn't require any surgery, and just medicine was enough.

"Of course, I'm personally hoping that you shake off the temptation of the worm and go through with treatment. However, I won't force you. Unless they were a relative, I wouldn't force treatment on a patient with no desire to be cured."

Five days, Kousaka repeated in his mind. He had to come to a decision by then.

"And I'll add just in case," said Urizane, "if you deny treatment, you will never meet Hijiri again. I don't know if she'll accept treatment or not, but in either case, it would be too dangerous to let once-infected persons stay together."

"Right," Kousaka said. "And my germaphobia and misanthropy won't be cured either."

"Indeed. And even if you do undergo treatment, until we can be sure the worm is fully gone from both your bodies, I can't let you come near Hijiri. I take it you understand?"

"...Yes."

Then Urizane seemed to remember something, opened a desk drawer, and handed Kousaka a photograph. It showed something resembling an inkblot used for a Rorschach test. From the progression of everything prior, Kousaka had some idea of what this unclear image was.

"Is this a photo of the worm?"

Urizane nodded. "Seeing that photo must make it feel a little more real, yes? Pictured there is two of the worms fused together. It was mentioned in Professor Kanroji's emails, but it seems when this parasite meets another in a person's body, their male and female sexual parts link up, and they adhere together in a Y shape."

Kousaka looked at the photo again. The worms, dyed a faint red, seemed to him to look less like a Y shape, and more like a heart drawn by a young child.

When Kousaka returned to the waiting room, Izumi and Sanagi sitting on the back sofa looked up. Kousaka smiled at Sanagi, but she averted her eyes and lowered her head.

"Seems you're finished," Izumi said. "I'll send you home."

"See you, Hijiri," Izumi said to Sanagi. It seemed she was staying here. Perhaps this was a hospital as well as a household, so she lived in this clinic.

Kousaka stopped in front of Sanagi, wanting to say something to give her relief before he left. But he didn't know how to speak to her.

No, he did know, really. Just say "Even after hearing all that, my feelings for you won't change, so don't worry." It was simple.

But Kousaka couldn't do that. He didn't have the confidence in his own feelings he did before.

Thinking back, it was all unnatural from the start, Kousaka thought. Why was Sanagi captivated by a good-for-nothing like me? Why did our compulsive disorders improve when we were together? Why did love bud between us with such a gap between our ages? There were just too many illogical aspects.

But if it was all an optical illusion caused by the worm, it lined up. Sanagi and I didn't fall in love. The worm inside me and the worm inside Sanagi fell in love.

He felt like he'd been expertly swindled. Like a swingback from the happiness he'd felt just a few hours ago, Kousaka's feelings rapidly sobered.

In the end, he left the clinic without a word to Sanagi. On the drive back, Kousaka just gazed out the window absentmindedly, but as they neared the apartment, he said to Izumi, "Um..."

"There was one thing I neglected to ask about the worm..."

"What?", Izumi asked, still looking ahead. "I'll answer if I can."

"Has its route of infection been identified?"

Izumi shook his head. "It's unclear. But Urizane's thinking it's probably oral infection. You were probably unlucky enough to eat food with the worm in it. You got any ideas?"

"Unfortunately, no."

"Thought so. ...Any other questions?"

"Does the worm spread from person to person?"

"It does." He replied quickly. Izumi seemed prepared for that question. "The adult worm resides in the central nervous system, but eggs and larvae move around the body through the bloodstream. ...But just living together won't spread it. Or else the worm wouldn't go to the trouble of making hosts fall in love. You get what I'm saying, right?"

"Yeah," Kousaka said. "It's sort of like a sexually-transmitted disease, isn't it?"

Izumi grinned. "If you don't wanna be shy about it, yeah. So, we know your worm didn't spread from Hijiri Sanagi. It's been lurking in your body since long before."

"I know. I wasn't doubting Sanagi. I was just curious."

Izumi's answer finally solved the mystery. On December 20th, Sanagi tried to kiss Kousaka while he was sleeping. But she caught herself just in time, and said: "I was just about to do something there was no coming back from."

Sanagi was probably plotting to spread the worm to Kousaka then. At the time, no one was aware that Kousaka was a host of the worm. And Sanagi knew that hosts of the worm would be brought together by a forced love.

Sanagi was planning to make their relationship perfect by spreading the worm to Kousaka. But just before she carried it out, she came to her senses. She awakened to the fact that she would be putting Kousaka's life in danger, couldn't bear to face him after that, and ran away.

That seemed to be the reality.

After dropping Kousaka off in front of the apartment, Izumi spoke.

"I'll come in the afternoon five days later. Get yourself ready by then."

"I don't think it'll take that long."

"Don't have to overthink it. It can happen to anybody. Alcohol, loneliness, and darkness can trick your eyes, and make you see a destined love. And when the two wake up sober the next morning, they notice the mistake they made. That's the same thing that's happened to you."

With no more to say, Izumi left.

Kousaka didn't go straight inside; he stood by the entrance and gazed at the light pouring out the windows of the apartment and nearby residences. Thinking how through those windows were people living totally different lives felt strange. It had been a long time since he was conscious of others' lives in that way.

Then out of nowhere, Kousaka thought about his mother's death.

I wonder. Perhaps I wasn't the only one infected with the worm then.

Perhaps my mother's suicide was caused by the worm.

In the month before her suicide, she was uncharacteristically kind, and treated him affectionately. That had never made sense to him all this time. The mother he knew wouldn't admit her own faults even if the world went topsy-turvy.

But if that were because of the worm, then he could accept it. His mother, made misanthropic by the worm, could only open her heart to Kousaka, similarly infected with the worm. The worm in his mother's body and the worm in his body were calling to each other.

Strangely, he felt cheerful. Now I can hate my mother without reservations, Kousaka thought. To her very last, she couldn't love Kousaka of her own volition. That fact cleared up a discontentment in his mind.