A unusual natural event in Kanazawa prefecture 22 years ago caused the soil to split and rise skyward to extraordinary heights, creating the solitary location known as The Lost Ground. Kazuma is a teenage mercenary who lives in the Lost Ground, searching for any labor he can find to make ends meet in the hard climate. He is one of the few humans who has the Alter ability, which allows him to plaster a metallic alloy over his right arm and body. When this mercenary comes into contact with HOLY, an order whose mission it is to suppress and capture what they term Native Alter Users, and one of HOLY's elite members, Ryuho, an epic rivalry ensues.