: Fyodor infects both the Armed Detective Agency’s leader, Yukichi Fukuzawa , and the Port Mafia’s leader, Ōgai Mori , with a "Cannibalism" virus.
: They investigate rumors of the previous Port Mafia boss returning from the dead, eventually uncovering a plot involving the investigator Arthur Rimbaud. Bungou Stray Dogs 3rd Season
The third season of , produced by Studio Bones and directed by Takuya Igarashi, aired from April to June 2019. Spanning 12 episodes, this season masterfully balances the franchise's signature dark prequel lore with a high-stakes modern-day battle for Yokohama. The Prequel: "Dazai, Chūya, Fifteen Years Old" : Fyodor infects both the Armed Detective Agency’s
Season 3 opens with a three-episode adaptation of the light novel prequel. Set seven years before the main story, it explores the chaotic "Dragon’s Head Conflict" and the first meeting between and Chūya Nakahara . Spanning 12 episodes, this season masterfully balances the
: Dazai, then a member of the Port Mafia, and Chūya, the powerful leader of a juvenile group called "Sheep," are forced into a partnership by the Mafia's leader, Ōgai Mori .
: The virus will kill both leaders in 48 hours unless one of them dies first, which would save the other. This forces the Agency and the Mafia into a bloody all-out war to protect their respective heads.