Kazuma fights with his entire body turned into a weapon, raw and ugly, no grace, just survival instinct sharpened into combat. The Lost Ground is a scar on the world, and everyone in it is scarred too; the show doesn't pretend their violence is noble. Two mercenaries on opposite sides of a war neither of them started keep finding reasons to fight each other instead of the people actually pulling strings, and that obsession is the only honest thing either of them has.

Twenty-two years ago, a strange environmental phenomenon in Kanazawa prefecture split the land and pushed it upward to extraordinary heights, forming an isolated region called The Lost Ground. Kazuma, a young mercenary, scrapes by there by taking any work he can get in a harsh environment. He is one of the few people gifted with the Alter ability, which lets him coat his right arm and torso in a metallic alloy. Everything changes when he runs into HOLY, an order dedicated to suppressing and capturing Native Alter Users, and into Ryuho, one of its elite members. From that meeting, a fierce rivalry takes shape in this sci-fi action adventure.