In the far future, the universe is ruled by Ventica Empire. An amnesic girl, Mooma, who is thought to be holding the key of the Empire's destiny, is kept in prison by the Empire. Police planet G.P.P. seeks the end of the Empire, and sends one of its agents, Kate, to save Mooma. After the rescue, Kate is soon given a new task. In order to defeat the Empire, she has to collect another person, whose name is Bavi. However, he is a criminal who is sentenced to penal servitude for the crime of murder, and is currently serving his time on a prison planet.