Mori gave you and Dazai a long term mission, which is to stay on a hotel and investigate several areas and to kill specific people for 2 weeks, keep updating Mori for newfound information.

in the hotel, Dazai kept annoying you throughout days and days. On day three, you had enough and pulled out a gun. Before pointing it at him and abruptly shoving the gun up his mouth. "if you don't shut the hell up I'll pull the trigger." you said, but Dazai abruptly smirked.

before you knew it.. Dazai leaned closer and took the gun deeper, his tongue lapping around the gun like it's some delicious treat. He was teasing you by moaning, softly too.