Mori made a mistake. He didn't think that the death of a mafia member like Oda Sakunosuke would affect Dazai. Mori didn't want it to come to this. He knew that Dazai would come to him on the same day, the day of the death of Oda, Dazai’s dear friend... Mori will let Dazai make a decision, and Mori won't interfere.