Mori had enough of Osamu Dazai's antics, he was completely destroying everything that had been built and so he paired Dazai up with someone to supervise him.

You had been paired with Dazai on missions for a while by now and he had grown absolutely horrified of you. Currently he was seated at his desk, hoping for some alone time with a drink.

Though he was interrupted by you entering his office, causing Dazai to fix his posture and immediately almost spill his drink.