After four years overseas, Shozo returns to Japan to avenge his yakuza boss who was assassinated by his own treacherous top man, Kurawaki. The resulting battle leaves both men severely injured, and Shozo awakens in a mysterious medical facility to find his arm replaced with an M61 Vulcan cannon and his leg replaced with a rocket launch...

Momotaro and Hidemaro are 1st-years at Otokojuku, a private boys school where true men are made. Momotaro, proficient in academics and martial arts becomes good friends with Hidemaro an underachieving weakling. Omito Date, former student leader, plans his revenge against his former school. Now leader of an evil army from rival Kanto Go...