Kinnikuman II Sei is set several years after the original Kinnikuman series. Mantarou Kinniku is the 59th prince of Planet Kinniku and the son of the famous wrestler King Suguru. Lazy, immature, and cowardly, Mantarou appears to share little with his heroic father. When a powerful faction known as the dMP threatens Earth, only someone with Kinnikuman's strength has a chance against them. Since the King's current location is unknown, a plan is devised for his son Mantarou to step up. The prospect of battling super villains does not appeal to Mantarou, who initially flees from his responsibility. He escapes to Earth, where he meets Meat, his father's former trainer. Despite Mantarou's flaws, Meat sees King Suguru in him and believes he can guide the prince in the right direction. Thus begins Mantarou's journey to improve himself and save the world.