Although Kid Muscle, who goes by the name Mantaro, is often seen as inept and unattractive, he is tasked with defending the planet against deceitful extraterrestrial wrestlers known as dMP. He teams up with the Muscle League, a collective of wrestlers from different worlds who prepare to safeguard Earth. By harnessing the coveted power known as "Ultimate Muscle," Mantaro undergoes a transformation that makes him almost unbeatable, enabling him to triumph over the dMP.