Sentan Island is a tiny island that is encircled by the Yuden Sea. It survives in a condition of dreamy peace, isolated off from the conflict between the Northern Government and the Southern Continent Free Zone. Akiyuki Takehara, our hero, lives on Sentain Island with his mother Fusa. He is presently estranged from his father, the local doctor Ryuzo, yet the father-son tie continues. Akiyuki comes to school one day after delivering Ryuzo the lunch that Fusa has cooked for him as usual, and is caught up in an explosion along with his buddies, Haru and Furuichi. The explosion causes a strange light to penetrate Akiyuki's arm, giving him great anguish. He doesn't have much time to think about it, though, because the white-haired girl who rode on the bus with him guides him to a power unlike anything he's ever known.