Dousetsu, Hamaji's older brother, resides in Edo after leaving her in the mountains with their grandfather. Upon their grandfather's death, he summons Hamaji to the city, intending to exploit her hunting skills. His goal is to kill remaining "fuse"—half-human, half-dog hybrids that consume human souls—claiming government bounties to gain wealth and samurai status.

As a ronin, Dousetsu initially appears immature and unfocused, living in modest lodgings. He frequents Edo's Red-Light District, where distractions from courtesans hinder fuse-hunting efforts. Yet he shows authentic concern for Hamaji's adjustment to the unfamiliar city. When loved ones face threats, his latent competence surfaces: he displays formidable swordsmanship, swiftly defeating foes and coercing officials into aid during crises.

His character shifts when learning local vendor Funamushi carries his child. Committing to responsibility, he marries her and vows behavioral reform to become a dependable father and husband. Post-conflict, he settles into family life with Funamushi and their newborn, whose notable strength draws wry acknowledgment.

Dousetsu remains instrumental in the fuse hunt, participating in tracking Itezuru and delivering the decapitating blow to secure their bounty. Though initially ambition-driven, his climax actions prioritize protecting Hamaji and allies, reflecting his deepened familial duty over personal gain.