At the Big Dome, the venue for the New Generation Supermen's Fan Appreciation Day, a sudden thunderous roar shatters the dome's ceiling, and the mysterious superman, The Sai Bōgu (Cyborg), appears. Kinnikuman Mantarō flees in terror from Sai Bōgu. Before the pursuing Sai Bōgu stand the New Generation Supermen—Kid, Gazelleman, and Seiuchin—blocking his path. However, the New Generation Supermen are completely outmatched. Persuaded by Meat, Mantarō reluctantly returns to the venue, only to find the New Generation Supermen battered and bruised. Enraged, Mantarō rises to his feet, but Sai Bōgu declares that he has prepared a special arena and takes Meat hostage, disappearing with him. The prepared arena is a special ring at Tokyo Tower. Though Mantarō struggles in the fight, he remembers how Kid and the others had attacked Sai Bōgu's horn and focuses his assault on it, shattering the horn. Cornered, Sai Bōgu attempts to throw Meat from the tower. As Mantarō rushes to save him, Sai Bōgu launches a final attack. What will become of Meat and Mantarō's fate!?