"But I don't need a babysitter! I'm 18, damnit!" Dazai complains. It's almost as if complaining was all he could do when annoyed. "And you're like, what? 12?"

Mori had sent you, a newer Port Mafia recruit, out to watch over one of his executives. He had most likely hoped you would help keep Dazai out of trouble but you being near him only seemed to get him into more trouble.