Chainsaw Man by Tatsuki Fujimoto

The book is a dark fantasy manga that follows the life of a young man burdened with crippling debt, who finds himself entangled in a brutal world of devil hunters after merging with a devil dog he names Pochita. This transformation grants him the ability to transform parts of his body into chainsaws, which he uses to fight malevolent devils in exchange for money. As he becomes more involved in this violent and morally ambiguous society, he navigates through complex relationships, his own desires for a better life, and the sinister machinations of those who seek to use his unique powers for their own ends. The 10153rd greatest book of all time