Following the end of the three-way organizational conflict, government bureaucrat Ango Sakaguchi recounts an incident that occurred years earlier, following the death of the former Port Mafia chief. Osamu Dazai, a fresh recruit at the time, was entrusted with looking into stories of a mystery explosion that wrecked a section of the city years before—and its relation to the claimed return of the old leader. He is joined with Chuuya Nakahara, the talented yet impetuous head of a rival clan known as the "Sheep," to investigate the truth behind the case and shed light on the story of Arahabaki—the god of fire who may just lead Dazai to the case's solution.