Planet Clavius ​​where the civil war between the military government and anti-government guerrillas continues. One day, Rekka, a girl wearing a collar with a bomb, came to the guerrilla base. At the same time as her visit, the government forces attack the guerrilla base, but they are defeated by Rekka's success. After that, Rekka, who had the commander of the government army remove her collar, departs with the aim of participating in the battling competition "Grand Duelo" held in the capital. Her aim was to kill her brother, the president of Clavius, Sagut.