During a worldwide broadcast of a Choujin Rugby match, the subterranean ruler Hydra King and his Underground Space Supermen abduct Robin Mask. Their plan is to draw out the Justice Choujins and then strike them using the Robin Memo, a document that reveals every Justice Choujin’s vulnerability. As the world watches the drama unfold on television, Kinnikuman and the Justice Choujins unite and head toward Planet Hydra.
