The office of Unicorn Chinese Branch is attacked by tank corps led by Red Cobra. Chang, its head, asks the help of the Japanese Branch. Azuma, Daisaku and Minami fly there on Giant Robo's back. The robot destroys the tank corps at once and Red Cobra is arrested. Asuma and Chang leave for New York by helicopter to take the prisoners to the headquarters, and Daisaku and Minami return to Japan with the robot. On their way, the helicopter is swallowed by Iron Power, enemy's new weapon with huge iron teeth. Azuma and Chang are taken to a secret base of the syndicate in the heart of Mt. Izu. Azuma, however, succeeds in communicating with the branch by a transmitter he has put in his shoe.
