Otoha Yousuke, born from an incestuous union between his mother and her yakuza-leader brother, carries congenital insensitivity to pain—a trait that forged his ruthless identity as a criminal enforcer. Unaffected by physical agony, he withstands brutal injuries without flinching, though this void of sensation fuels emotional numbness and alienation.

Bound by contract to Yurine, Tokyo’s spiritual embodiment, he serves as Karas, the city’s supernatural guardian. Tasked with shielding humans and yōkai alike, he battles his predecessor Eko, who plots humanity’s annihilation through mechanized demons called Mikura.

Otoha shifts seamlessly between forms: an armored warrior wielding a katana and explosive shuriken, a jet, or a car, all armed with energy-based weaponry. His combat thrives on preternatural speed and precision, unchecked by pain, yet this advantage spirals into life-threatening recklessness when stripped of his Karas abilities. A volatile "rage mode" surges during dire clashes, amplifying his ferocity.

His past as a yakuza weapon resurfaces when he executes his brother-father for murdering a trusted ally, a pivotal act in his shift from violent enforcer to Tokyo’s reluctant protector. Though stoic, he harbors compassion, covertly running a hospital for wounded yōkai and earning the moniker "Doctor Karas."

During Eko’s assault, losing Yurine severs Otoha’s powers until his defiant vow to defend Tokyo reignites their bond, restoring his strength and resolve. Their final clash forces him to confront Eko’s prophecy that centuries of duty will corrode his ideals. Victorious yet haunted, Otoha continues safeguarding Tokyo’s rebuilding populace, clashing with authorities targeting yōkai. His journey weaves trauma and redemption, prioritizing protection over vengeance as he reconciles fractured loyalties and purpose.