Im-sol is an ordinary student who is about to graduate from college.Hiding the fact that she is a fan of Ryu Seon-jae, the fifth member of the Idol group Potato Pancakes',Right now, she is doing cosplay in public. -BREAKING NEWS- Ryu Seon-jae, a member of the Idol group, Potato Pancakes', is dead!Then one day, because of an accident, Ryu Seon-jae died and Im-Sol, who was in sorrow, accidentally picked up a pocket watch and made a time leap to the past, six years ago..Gray pants, white shirt, beige knit vest.No matter how much she blinked and squinted at him, he was standing alive, right before her."Seon-jae, that's Seon-jae. Ah, it's him. He's real."Ryu Seon-jae, a high school student who she only saw in the picture, was right in front of her eyes.This may be an opportunity.An opportunity to prevent Ryu Seon-jae from joining Potato Pancakes and becoming its 5th unlucky' member.An opportunity to save Ryu Seon-jae, who died at the age of 23 with no luck because he took a wrong cold medicine.Eighteen to live again, with only one goal.It is to save Ryu Seon-jae!To save the best in the past,Im-sol's struggling ordeal, The Best of Tomorrow.'