Kai Eto may look like a squeaky clean kid, but the Greater Kanto Narcotics Control Division's new investigator hides a violent alter ego and a dangerous past. Together with his stoic partner Hal Kurabayashi, Kai is assigned to track down and stop the distribution of a dangerous new drug—Dragon Speed. Kai has a mental break after shooting a suspect. Fragments of memories surface as he tries to resurrect his past. As more details emerge, Kai must confront his other personality and its origin, which holds the key to his relation with the Ryugen and the secret of "switch."