The ninja's beloved Grandpa Kai is murdered by the yakuza, and now it's payback time. The battle pits Nodoka Matsumoto, the compassionate ninja, against the yakuza heavyweight Kousei Yuzawa. The action takes place in the seedy underground below Tokyo's infamous Kabukicho. Seeking an advantage, the yakuza dope up with Hell's Coupon--a drug that gives them ninja powers. Will that be enough to prove they are the strongest of the criminal underworld?