Heroic Chainsaw (Izuku Midoriya. The Hero of Hell)

Izuku Midoriya was a young boy who aspires to be a hero that saves others, Just like his Idol, All Might. But when his quirk results came, It was revealed that he was Quirkless

Ever since that day, was hated, bullied, ignored and treated as an outcast because he was Quirkless but even with no powers, He wanted to be a hero. A tragedy truly yet instead of dealing the backlash of being Quirkless alone, He gets a small companion, An animal with a Mutant quirk. A chainsaw dog which he named Pochita

Pochita was his best friend and liked Izuku more than anything else. Yet after being kidnapped by the Yakuza and getting killed. Pochita revives and makes a deal with him

"I'll revive you and be your heart, In exchange. Fulfil your dream of becoming a hero, Izuku"