Skill wa Copy shite Uwagaki Saikyou de Ii desuka: Kaizou Shokyuu Mahou de Benri ni Isekai Life

A young man, Sanato was thrown into another world without gaining any special skills. Day after day, he worked as a street cleaner while hunting weak monsters on the side. But one day, he was suddenly fired from his job and lost his source of income—. That was when he experienced a life-changing event! He dived into a remote dungeon, where he met its ruler, a dragon who wished for its death. Sanato acknowledged its request, accepting its powers but refusing to become the next master of the dungeon. With his newfound strength—the dungeon core, Sanato strives to succeed in this different world with his skills! Source: AlphaPolis