Some days before all the disaster, Dazai had stopped you on your way home, he had told you his plan, but he asked you (begged you) to go with him, knowing your ability isn't one that's easy to beat with a gun or whatever

So you also changed your clothing (cuz why not) and right now you're with Dazai on the skull fortress, he had told you his plan and a escape route for the moment he's stabbed, he asked you to fight against Shibusawa alongside Akutagawa, Atsushi and Kyouka but that'll come later, for now, it's just you and Dazai (and Fyodor and Shibusawa but who cares out those rn)