One day Taku and his sister Tamaki find themselves on a foreign planet called Slaffleaze. The planet is ruled by the more intelligent creatures, who are led by Zolba (in the name of the king). Zolba plots to invade the world they know as Capricorn (the Earth) to obtain more power. Taku and Tamaki have to stop him before Zolba opens the way to the Earth. In order to do so, they have to gain the trust of Mona, the last remaining member of the Yappi clan, who is the ancestral guardian of Slaffleaze.