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.

Hal survives an assassination attempt, but it seems he may not have been the target. Clues point to the 'switch', but no one seems to know just what that means. The Ryugen, however, do know something and use that knowledge to entrap Kai and flip his switch.