Following the suicide of the Pyrotechnician, Narihisago is placed in solitary confinement and members of the investigation team feel on edge over his actions. However, an attempt to find a replacement detective proves unsuccessful, and the team is forced to work with Narihisago again. The target is the Gravedigger serial killer, who buries their victims alive and livestreams their dying process. Sakaido discovers the killer is a depressed and lonely man from the victim's neighborhood, but Kazuo realizes he is a copycat killer and the real serial killer remains at large...