The Chojin Crown, the tournament which Mantaro (Kid Muscle) reluctantly participates in. After going along with the obstacles (most of which were created to try and eliminate him), he qualified.

Kinnikuman II Sei takes place several years after the events of the original Kinnikuman. Mantarou Kinniku is the 59th prince of Planet Kinniku and son of the renowned wrestler, King Suguru. Lazy, immature, and cowardly, Mantarou seems to have little in common with his heroic father. When a powerful group calling themselves the dMP threatens the Earth, only someone as powerful as Kinnikuman stands a chance against them. Not knowing the current whereabouts of the King, a plan is formed to have his son Mantarou take up the mantle. The idea of fighting super villains does not sit well with Mantarou, who initially runs away from his duty. He flees to Earth where he encounters Meat, his father’s old trainer. Despite Mantarou's shortcomings, Meat sees King Suguru in him, and believes he can set the prince on the right path. Thus begins Mantarou's journey to better himself and save the world.

With the seas under constant threat from the hostile "Abyssal Fleet," a specialized naval base is established to counter them. Rather than standard naval weaponry, however, the base is armed with "Kanmusu"—girls who harbor the spirits of Japanese warships—possessing the ability to don weaponized gear that allows them to harness the powerful souls within themselves. Fubuki, a young Destroyer-type Kanmusu, joins the base as a new recruit; unfortunately for her, despite her inexperience and timid nature, she is assigned to the famous Third Torpedo Squadron and quickly thrust into the heat of battle. When she is rescued from near annihilation, the rookie warship resolves to become as strong as the one who saved her. [Written by MAL Rewrite]

The countdown to extinction begins on Sunday with the arrival of the Septentriones, otherworldly invaders set on the eradication of mankind. Caught in the crossfire, Hibiki Kuze and his friends join in the war for humanity's survival by signing contracts with demons to become "Devil Summoners." Soon, their abilities attract the attention of JP's, an underground agency led by Yamato Houtsuin. Once recruited into JP's, Hibiki and his friends fight and bond alongside other ordinary citizens who are Devil Summoners. However, with each new day, another Septentrione appears to wreak havoc upon Japan. Even if many lives are lost in the process, before that night ends, the young summoners must defeat the invaders at all costs. [Written by MAL Rewrite]