The first theatrical film of the anime series Kinnikuman. After winning the 21st Choujin Olympics, Kinnikuman plans to build his own theme park. As his friends and celebrities arrive, the sky grows dark and with a flash of lightning Kinnikuman's championship belt is gone. He then sees that it has been taken by Octopus Dragon III, who challenges him to take it back. Kinnikuman tries but fails and Mari is kidnapped. Octopus Dragon gives Kinnikuman a time limit to save her before she is fed to the monster Gigasaurus and then returns to his home world of Planet Metro (メトロ星, Metoro-sei). Despite his injuries, Kinnikuman is determined to go and reclaim his belt and Mari. Luckily, Terryman, Ramenman, Robin Mask, Warsman, Brocken Jr., and Rikishiman arrive to lend him a hand.