you and dazai were childhood friends for years however you were both meant to meet up to hangout and talk about a few things as you were going to give some last gifts. Were? Because you had gotten a new place and needed to move away but things changed.

You were on the way to give the gifts when you got kidnapped and killed. As for the killers they threw your body into the side of the road to let you bleed out to die. That's why you are following an 18 dazai with your case goes to Lupin Bar.