Denji, yearning for a tranquil life with his crush, is coerced by the yakuza to exterminate devils for debt repayment. Armed with his devil companion Pochita, he dives into gruesome deeds for money. Tragically betrayed and slain by a devil under yakuza control, Denji experiences a bizarre resurrection as Pochita fuses with him, granting him the fearsome abilities of the chainsaw devil. Transformed and ruthless, Denji swiftly eliminates foes, attracting the attention of devil hunters from the Public Safety Bureau who recruit him. Empowered and resolved, Denji vows to realize his modest desires with unwavering determination, now equipped to confront even the most formidable adversaries.