Takeru Tachibana, a teenager, embarks on a mission to rescue his sister, Sayoko, from the cruel arena of cyborg dogfighting. A bombing in their town kills their parents and injures Takeru at the age of 10. Sayoko's decision to sell her brain to the Albion Corporation for Takeru's medical expenses turns into a disastrous transformation into a cyborg. She becomes a champion in the dogfighting world but Takeru halts her reign. However, Sayoko's life hangs by a thread as her cyborg brain is configured to destroy itself unless she returns to the ring or is cured within a week. The story's other characters also carry burdensome histories, and the Albion Corporation is relentless in reclaiming its stolen possession.