Following the advice of new friends, Roue and Chrome set off to find Heaven Land, a gear utopia, in order to revive Uncle Zett. But when a threatening gear blocks their path, Chrome unknowingly takes on a vicious combat form that frightens Roue. What other secrets might Chrome have that he doesn't even know himself? And when their next lead on Heaven Land brings them to Valhalla, a coliseum of warriors, what horrors will Chrome unleash when he's forced to fight once more?
Nearly 200 years after the destruction of humanity in World War III, Roue lives a happy life exploring the ruins of civilization with her "uncle," a robot named Zett. But when their peaceful life is threatened, Roue must trust the mysterious robot Chrome to bring her family together again.