Deep at the base of a cliff is a world called Votoms. Aki Tesuno, whose thoughts are always directed at the Top, the world at the height of the cliff, lives in Votoms. Thanks to his inborn AT (Altro) piloting ability, Aki is nicknamed Tumbler. He receives a request from Top to save a girl who has been kidnapped in Votoms by a man named Deerheart. Aki accepts right away. With his friend Avy they head for the ruins known as Island and confront Deerheart.