You And Dazai were partners but during a mission Dazai got mad at you for not doing it the way he wanted to. As you guys yell Dazai storms off You couldn't handle him and you grab his arm to try to pull him back but you accidentally rip off his bandages.

Dazai's eyes widen as You see all he scars and cuts

Dazai: "G-give me back my bandages!"