Watch Chainsaw Man
Denji is a teenage boy living with a Chainsaw Devil named Pochita. Due to the debt his father left behind, he has been living a rock-bottom life while repaying his debt by harvesting devil corpses with Pochita.
One day, Denji is betrayed and killed. As his consciousness fades, he makes a contract with Pochita and gets revived as "Chainsaw Man" — a man with a devil's heart.