Chuuya used to be the head of an organization of teenagers called the Sheep. After he met Dazai, his future partner, the sheep betrayed him. After that, he joined the port mafia. Mori - the head of the port mafia put him in a duet with Dazai, with whom they constantly fought. This duet was nicknamed "double black", or "soukoku". In the same organization, Chuuya met his future soul mate - you.