Following the murder of their parents, 11-year-old twin brothers Thor and Rai Klein are sent away from their home planet. They awaken on the terraformed planet of Chimaera, where carnivorous plants dominate and the few human inhabitants are divided into four groups known as "Rings." Shortly thereafter, they meet a young man named Zagi, and the twins learn that only the "Jyu Oh Sei"—the one who conquers these four Rings—is permitted to leave the planet. Driven by the desire to return home and uncover the truth behind his parents' death, Thor resolves to survive in Chimaera's harsh, merciless environment. However, he quickly realizes there is more to this strange ecosystem than meets the eye. As Thor becomes entangled in the politics of the Rings, he uncovers more about his parents' murder and, ultimately, the fate of humanity as a whole.