Octopus Dragon, Harigorasu, and Ukon are all kaijū from the infamous "Roots Island" two-part story from the original manga that does not appear in recent reprints.
As his friends and celebrities arrive, the sky grows dark and with a flash of lightning Kinnikuman's championship belt is gone.
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).
Although Rikishiman manages to grab hold of the wall of the valley, he tells Kinnikuman and the others to go on without him as it would take too much time to save him.
After a comical scene where Kinnikuman mishears Ukon's name as unko (うんこ,, poop), Ramenman and Brocken Jr. volunteer to take them on while the others continue on the journey.
Kinnikuman and Terryman finally find Mari but are immediately challenged by Octopus Dragon to a tag match against himself and Mouko-seijin.
After a fierce struggle, Terryman defeats Mouko-seijin with his trademark Calf Branding but is shot by Gammalar before he can help Kinnikuman.
They almost kiss but are interrupted by a female dinosaur emerging from the ground beneath them and confessing her own feelings for Kinnikuman, ending the film on a comical note with all the characters laughing.