As a young boy, he inherits his father's debts from the Yakuza. After meeting Pochita, he becomes a Devil Hunter for the Yakuza in an attempt to clear his debt. Once the Yakuza, under the control of a Devil, betrays him, he dies and Pochita becomes his heart. He is then revived and can become the Chainsaw Man by pulling a cord on his chest. After meeting Makima, he became a Public Safety Devil Hunter as a member of Tokyo Special Division 4.