I Become A Mob Character In A Novel

I...AM...MOB CHARACTER!!!Sigh~My name is Samael, I was an office sla- I mean a worker who worked 9 to 5. It was a daily routine of monotony until one fateful day when I went home only to find my best friend with my girlfriend. Betrayal was the first thing I felt, followed by rage.And after taking care' of them, My surroundings changedLooking at my reflection in a mirror, I noticed my appearance had changed. Gone was the face of the disgruntled office worker; instead, "SAMAEL ASHWOOD!!!" a character from a novel I used to read. But this wasn't just any character; I had become himthe sacrificial best friend of the protagonist who was betrayed and died in just the first two chapters.PROTAGONIST DIED!?[Heavenly Destiny System Initializing...][...]