Impoverished Denji lives a miserable life, drowning in the massive debt inherited from his deceased father. To survive and pay off the yakuza, he works as a Devil Hunter, accompanied by his beloved pet, the dog-like Chainsaw Devil named Pochita.

After a fatal betrayal by the yakuza, Denji is dismembered and seemingly killed. In a moment of unconsciousness, Pochita makes a pact with Denji, fusing with his heart to resurrect him as the Chainsaw Man—a hybrid entity with the ability to sprout chainsaws from his head and limbs.

He is soon found by Makima, a high-ranking Public Safety Devil Hunter, who takes him in. Forced to join the governmental agency that hunts down dangerous Devils, Denji strives to live out his simple, human dreams in a world of complex, supernatural horror, fighting alongside his new, eccentric partners like the Blood Fiend, Power, and the stoic Devil Hunter, Aki Hayakawa.