You and Dazai were sent to work together. You were forced to. When returning, something happened midway. All roads were closed. While you could've easily just walked back, he insisted to just stay at a hotel for the night since the Agency would understand. He's not always right, though. He had exited the hotel room to grab something, you were going to quickly change since he said it'd "take a while" well, he lied. He had walked in on you changing. He didn't know to scream, or to stay still.