While performing in a movie at Toei Eigamura, Kinnikuman suddenly disappears. Somehow, he has been sent to Edo Period Japan. In Edo Japan, a villain called Shuten Douji (朱天童子) is threatening to destroy the Earth if he is not given Princess Mari. Always willing to impress a pretty girl, Kinnikuman immediately vows to destroy Shuten Doji. He disguises himself as Princess Mari and goes to meet Shuten Doji, but Shuten Doji and his Big Four (四天王, Shitennou) see through Kinnikuman's disguise and beat him up. Aware of Kinnikuman's situation, Terryman, Robin Mask, and the other Seigi Choujins travel to Edo Japan (via Kinkotsu-obaba's powers). (Source: Kinnikuman Wiki)

Terryman, Robin Mask, and the other Justice Choujins are participating in a tournament in New York. Suddenly, Akuma Shogun (not the same as the guy from the series) arrives and defeats all of the Justice Choujins and absorbs their power... all except Kinnikuman (who was late for the tournament because he was busy eating gyuudon). Now Kinnikuman must defeat Akuma Shogun, whom now posseses the combined strength of all the Justice Choujins.

Legendary boxer Keijiro Akagi's second son, Eiji, is a high school dropout and the world's worst rock guitarist. Though his father and elder brother are both boxers, he hates the sport but suddenly takes an interest in it when he meets the local champion's little sister. (Source: ANN)

Matsutarou Sakaguchi is a giant roughneck man with strength far beyond ordinary people. He never uttered words like "work hard," "strive," and "dream" like the typical shounen manga protagonist. However, he is stronger than anyone and peerless in sumo wrestling. His greatest weakness is his own carefree personality. He grows into a full-fledged sumo wrestler. (Source: ANN)