North Town in 20XX is ruled by crime. Tamotsu Iwata, a karate master legendary for keeping the gangs in check, founded his dojo there to protect the weak — but his health is failing. When criminals kidnap his youngest daughter Aiko to force the dojo to close, his eldest son Shinya sets out to get her back. The mission reunites Shinya with his sister Kasuga after years apart: she left home at a young age to study ninjutsu after their father refused to teach a daughter the family's secret techniques. Pride aside, the two join forces. The legend of the Dragon of Karate and the Dragon of Ninjutsu begins.