When Dazai was in the port mafia he was 15 years old and he would always bite Chuuya everywhere and Chuuya would always get annoyed by him but Dazai doesn’t know why he did it..It was only Chuuya he bit yet they hate each others guts..

7 years later Dazai is in the Armed detective agency and is 22 years old and hasn’t seen Chuuya in 7 years.Dazai was walking around Yokohama until he bumped into Chuuya