Deprived of a typical teenage existence, Denji is burdened solely by the crushing debt left by his irresponsible father. His only companion is Pochita, a chainsaw devil he keeps as a pet, and together they hunt devils for cash that invariably flows into the yakuza's coffers. Denji's aspirations are limited to a modest, pleasant life: one featuring tasty meals and a lovely girlfriend. However, a greedy betrayal by the yakuza results in Denji's brutal and premature death, extinguishing any hope of him ever finding happiness. Surprisingly, an old contract enables Pochita to fuse with the deceased Denji, granting him devil powers and transforming him into a hybrid capable of turning his body parts into chainsaws. Since Denji's new abilities present a major threat to society, Makima, an elite devil hunter from the Public Safety Bureau, takes him in, allowing him to survive on the condition that he obeys her orders. Driven by the promise of a fulfilling life with an attractive woman, Denji gives his all and fights fiercely to turn his naive dreams into reality.