Suguru Kinniku, known as Kinnikuman, is the prince and eventual king of Planet Kinniku. Accidentally abandoned on Earth as an infant when his parents mistook him for a pig during space travel, he grew up alone. His early Earth years were marked by poverty, academic failure, and unsuccessful attempts to establish himself as a capable superhero despite inherent strength. He ultimately became president of a gyudon lovers' club. Initially characterized as clumsy, emotionally immature, and arrogant, he chased women, switched jobs frequently, and avoided serious responsibility. Cowardice defined his early fighting spirit; he typically refused combat unless offered incentives and was universally dismissed as a worthless superhero.

His trajectory changes when Alexandria Meat, a servant from Planet Kinniku, recruits him to reclaim his homeworld from the usurping King Tone. Though reluctant, Kinnikuman returns and enters wrestling tournaments to prove his worth. His fighting style evolves from simple giant-form kaiju battles fueled by garlic to specialized wrestling techniques. Key abilities include the Kinniku Buster (a piledriver variant), Kinniku Driver (a leg-trapping tombstone piledriver), Muscle Spark (a multi-bounce chest slam into a submission hold), and FuuRinKaZan (a four-move combo). Despite growing prowess, he retains clumsiness and occasionally employs unconventional tactics like using flatulence for propulsion or distraction.

Personality development unfolds through tournaments and rivalries. He transforms from a self-centered underdog into a justice-driven leader, especially evident during the Chojin Olympics. His inherent nobility surfaces during crises, intensifying against dishonorable foes. He forges deep bonds with former enemies like Ramenman and Warsman, and allies like Terryman, who becomes his inseparable tag-team partner. Their friendship, built on unconditional trust, endures into later life. Romantically, he initially dismisses Bibimba, an assassin sent to kill him, but gradually reciprocates her feelings. They marry, and Bibimba later sacrifices herself for him during the Survivor Match for the Kinniku Throne arc. Their son, Mantaro, is born years afterward.

Kinnikuman's crowning achievement is winning the Survivor Match against five pretenders, securing his kingship. Post-coronation, he returns to Earth for a farewell wrestling match against Terryman, symbolizing closure to his active career. Decades later in the sequel *Kinnikuman Nisei*, he is physically diminished by age, losing muscle mass and developing a large stomach. He avoids discussing his past glory with Mantaro, intentionally destroying records of his achievements to facilitate his son's normal upbringing. Consequently, Mantaro views him only as a bumbling, simple-minded father, unaware of his legendary status. Despite frailty, he retains technical wrestling knowledge, employing submission holds and grapples during a spar with Mantaro. The Kinniku Buster becomes a dangerous forbidden technique due to the toll it takes on his aged body.

A 2011 manga revival depicts him temporarily regressing into cowardice after prolonged peace, doubting his past victories as luck-dependent, setting the stage for renewed growth that echoes his original arc. Throughout his life, his appearance fluctuates: he wears a signature mask featuring exaggerated lips and a forehead "meat" kanji symbol, while his rarely seen unmasked face is notably handsome. In old age, his physique shifts from muscular to a pot-bellied, frail frame, though his commitment to protecting the universe endures.