División

What would happen if you were reincarnated in the past instead of future? Cain has noticed how different he was since he was a child. Unexplained phenomenon keeps happening unto him and a certain shadow keeps lurking in the dark. And now that he's older, a sudden heart attack claimed his life. He died at the age of 35 and woke up immediately realizing he's in the past. What brings him in the past? How did that happen and why was he reborn in the first place?