Dazai, Chūya, Fifteen Years Old.Ango narrates a story of the worst bloodshed incident in Yokohama, where 88 corpses were produced. Prior to the events of the first season, eight years ago, Mori has just taken leadership of the Port Mafia, having secretly killed his predecessor who was showing self-destructive tendencies. Dazai acts as Mori's witness. A year passes, and Dazai is sent to examine strange rumours of the Predecessor's revival within a Suribachi City, a city built in a crater produced after a massive explosion eight years ago. Suribachi is also currently an area of conflict between the Mafia and 3 other organisations: Gernhardt Secret Society (GSS), Takasekai and the Sheep, a group of juveniles. There, 15-year-old Chuya appears to battle Dazai as the leader of the Sheep, believing that the Port Mafia is looking into the rumour of 'Arahabaki'. Arahabaki was supposedly summoned by the hatred of a tortured soldier and caused the explosion of Suribachi City eight years ago. They fight briefly before witnessing the Predecessor appear before their very eyes. Chuya is then captured and brought to the Mafia headquarters. Mori decides to have him and Dazai work together, with the Sheep members' lives on the line, to uncover the truth behind the seemingly connected rumours of the Predecessor and Arahabaki.