In a world where power is everything and hunters climb dungeon towers to survive, 18-year-old Jiva awakens a rare B-rank skill—Upgrade. But unlike flashy fireballs or sword mastery, his ability is non-combat… and comes with a terrifying price. To evolve weapons, artifacts, or even other skills, Jiva must sacrifice parts of his own body. A finger. A tooth. Blood. Flesh. While others laugh at his "useless" skill, Jiva walks a brutal path—trading his pain for strength.