Karas, formerly Otoha Yosuke, began life as a yakuza enforcer under the command of his brother—later exposed as his biological father. His congenital inability to feel pain, a consequence of incestuous parentage, forged him into a ruthless assassin. After surviving his father’s betrayal and a near-fatal ambush, he lingered in a comatose limbo until Yurine, the living embodiment of Tokyo’s spirit, resurrected him as the city’s Karas: a spectral guardian sworn to defend humans and yōkai alike.

Reborn with shapeshifting armor that morphs into vehicles or aircraft, Otoha wields a katana empowered by Shinto rites. His arsenal includes accelerated healing and the Hiei Zangetsu state, marked by crimson eyes and a blade that morphs into an executioner’s tool. Though impervious to pain, his flesh remains fragile, forcing dependence on regeneration to survive catastrophic injuries.

Once consumed by vengeance against his yakuza kin, Otoha pivots to thwarting Eko, a rogue Karas bent on exterminating humanity through mechanized demons called Mikura. Reluctantly allying with Nue, a defecting Mikura, and Homura, a rival city’s guardian, he navigates distrust to counter Eko’s onslaughts. A critical blow comes when Eko severs Otoha’s bond to Yurine, stripping his powers. Near death, Otoha revives through raw will, resurrecting Yurine and reclaiming his mantle—a transformation from solitary avenger to selfless sentinel.

Beyond battle, Otoha tends to yōkai in a clandestine hospital, balancing violence with quiet stewardship. Bonds with allies like Fate Testarossa, whom he mentors, and Takaya Aiba, a sparring partner turned confidant, expose his evolving empathy. As Shinjuku crumbles and losses mount, he grapples with humanity’s fear of yōkai yet clings to his vow as Tokyo’s protector. His journey culminates in a bittersweet triumph, the city’s ashes cradling his unyielding pledge to bridge its fractured worlds.