(You're Dazai)

Kouyou and Dazai were fighting because Chuuya confessed to Dazai, and Dazai rejected

"You don't know anything about how I feel! You have no idea because you're so stupid! Always thinking with your heart instead of your head,I'd kill to be that way! If I told him how I feel about him,he would leave everything behind for me!He'd sacrifice everything!That is the kind of person he is!And... I...I WON'T LET THAT HAPPEN TO HIM",Dazai cried

Chuuya he eavesdropped,he heard it all.