Cutthroat, alias Satsujinki, is a notorious criminal imprisoned for 967 years after committing 999 murders. His execution is disrupted by Akudama operatives hired anonymously, enabling his escape. During the rescue, he murders the overseeing police chief, claiming his 1,000th kill.

He exhibits a childlike persona, humming rhymes and adopting playful mannerisms in calm moments—a stark contrast to his sadistic nature. Violence ignites his euphoria, particularly under the influence of red, which he associates with "blooming flowers." He fixates on individuals displaying crimson halos, interpreting them as targets destined for slaughter, and compulsively manipulates red-lit environments, even sabotaging infrastructure to indulge his obsession.

Standing tall with pallid skin, he has white neck-length hair, violet eyes, and a mole beneath his left eye. His attire—a white overcoat, dress shirt, trousers, and black tights—is accented by bandages wrapping his left hand. Surgical stitches trace his reattached legs, a remnant of injuries sustained during combat.

He develops a warped bond with Swindler, feigning protectiveness while awaiting the maturation of her red halo to kill her. His manipulations include exploiting the immortal Brother as a shield during clashes with the Execution Division Master, impaling the child to strike his foe. A lethal combatant, he wields knives with precision, endures extreme pain, and survives catastrophic injuries, including high-impact falls.

His final act unfolds at Execution Department HQ, where he ambushes Swindler after slaughtering Executioners. Confessing his intent to kill her upon witnessing her halo’s zenith, he is disarmed and fatally stabbed by Swindler. He dies praising the radiance of her crimson aura.