A host of demigods have inherited the world after the Demon King has died, and a battle to determine the mightiest ensues.

Antigamente existia a 'mágica' e respeitada vila do "Céu", uma fortaleza flutuante. Acreditava-se que ela era o centro mais protegido do mundo, pois era uma combinação de gigantescas muralhas impenetráveis, e havia um poder de flutuação que era sustentado por um outro mistério, o 'Chakra Negro'. Mas por algum motivo a vila oculta do "Céu" foi extinta... a "Vila Flutuante" sumiu com tudo e com todos, o que restou foram somente ruínas e algumas histórias. Agora ela reaparece trazendo à tona laços inseparáveis.

A strange environmental phenomenon 22 years ago in the Kanazawa prefecture caused the land to split and protrude upwards reaching unprecedented heights, creating the secluded area known as The Lost Ground. Kazuma is a young mercenary who lives in the Lost Ground, looking for any work he can find to sustain his livelihood within the harsh environment. He is one of the few people that are gifted with the Alter ability, which allows him to plaster his right arm and torso with a metallic alloy. When this mercenary encounters HOLY, an order whose purpose is to suppress and capture what they call Native Alter Users, and one of the elite members of HOLY, Ryuho, an epic rivalry begins.