The story involves Kinnikuman (real name Suguru Kinniku), a clumsy, foolish superhero who discovers that he is the missing prince of the planet Kinniku (known for producing the greatest superheroes in the universe). Since he is a clumsy fool, however, he must prove himself worthy of the throne. To do so he enters wrestling competitions and battles evil Chojin, culminating in a tournament between Kinnikuman and five pretenders to the throne: Kinnikuman Big Body, Soldier, Zebra, Mariposa and Super Phoenix. Many of Kinnikuman's allies begin as villains (Ramenman, Buffalo Man, Ashuraman and Warsman) or arrogant heroes (Terryman, Robin Mask and Rikishiman). The heroes and villains are collectively known as Chojin, which literally means "supermen".
In the beginning of the series, Suguru fights Kaijū by eating garlic and growing 30 meters tall. Despite his great strength and skill, Suguru is quite clumsy by nature. This side of him causes most people to fear him more than the monsters he fights (due mostly to the possibility of him crashing into buildings while in his giant form). He is so clumsy that, at times, regular people are capable of besting him in fights. He has even said on one occasion that although Chojin's wounds heal much faster than human wounds, when he gets hurt it takes longer to heal than a human, probably as a result of how he takes his training and fitness much less seriously than most choujin. He is also very arrogant and believes himself to be more popular than he actually is. He gets daily reminders of the truth, however, when people run from his ugly face or his garlic breath.
Suguru's favorite food is gyūdon, and he will do almost anything if he is offered just one bowl. Though he mostly eats gyūdon, he also pigs out on a wide variety of other foods, and when he is not eating he is usually watching TV. He "trained" for the 21st Chōjin Olympics by eating chips and watching TV. He is stationed in Japan in Beverly Parkand lives there with Meat.
Suguru is also a bit lecherous and has been known to take part in matches he previously refused to simply because a pretty girl asked him to change his mind. Suguru flirts with every girl he sees, and has on numerous times tried to peep on his friends Mari Nikaido and Natsuko Shono. Unfortunately for him, no girls find him in the least bit appealing except for Bibimba.
However (and ironically), when Bibimba first shows up it is a one-sided love on her part and he finds her more annoying than cute. But by the time of the Seven Devil Chōjin Arc he seems to acknowledge her as his betrothed. During the Survivor Match for the Kinniku Throne Arc, he showed great concern for her when she threw herself from the stands and later admits that he believes they are bound by the red string of fate. Oddly, Bibinba is for the most part left out of the anime, and Mari, whom had always shown more interest in Meat, becomes his main love interest.
His personality is reflected in his voice in the anime, which deviates between high and screechy and low and serious.
In Kinnikuman Nisei, Suguru has lost his muscles and become skinny and flabby, but is still quite powerful. As he explains to a doubting Mantaro, while old age has robbed him of most of his physical prowess (thus making Suguru unable to perform many of his most famous moves) he's still able to employ grapples and leves, and his knowledge and coordination have been left unaffected. He has taken on a lot of the same characteristics his father had and is usually bickering with his son. Unlike with his father though, Suguru has a great deal of respect for Mantarō, and although Mantarō finds him lame they maintain a rather healthy father/son relationship. While Mayumi was mostly a comically uncaring father in the early chapters of the original manga and a strict father in the latter parts, Suguru, "a child at heart" (according to the American dub of the anime) tried to get in Mantaro's good graces by spoiling him and hiding from him every trace of his past as a champion, wishing to be no more than a mere father to him. Even when Mantaro eventually learned of his father's past, he still held to the memories of his goofy, caring, simpleminded father.
- Height: 185 cm.
- Weight: 95 kg.
- Classification: Justice Chojin.
- Chojin Power Level: 950,000 (boosted up to 70,000,000 with the Kajiba No Kuso Djikara)
- Kajiba no Kuso Djikara (火事場のクソ力, Kajiba no Kuso Djikara), Kinnikuman's Burning Inner Strength. Originally called the Kajiba no Baka Chikara (火事場のバカ力), it is literally a burning display of power. It is Kinnikuman's ability to improvise during battle despite his ignorance, last longer than a Chojin with a mere 950,000 power should, and overcome great obstacles. His great luck is also believed to be part of this. Though a more literal translation would be Burning Idiotic Strength, most English speaking fans prefer Burning Inner Strength. In the English VIZ manga, this ability is referred to simply as "The Fire," and in the English dub of Kinnikuman: Nisei is called "Ultimate Muscle."
- Kinniku Buster (キン肉バスター, Kinniku Buster), Kinnikuman's trademark (and most popular) attack and one of the 48 Killer Moves. First used during the fight with . He places an opponent's neck on his shoulder and grabs their thighs. He then jumps up and lands in a sitdown position, causing damage to the neck, spine, and groin. This move is also used by his son .
- Neo Kinniku Buster (新（ネオ）キン肉バスター) First used during the fight with . While upside down (or reversing a Kinniku Buster), Kinnikuman does a standard Kinniku Buster hold. He then spins around violently, causing himself and his opponent to fly upwards and land on the ceiling.
- Double Kinniku Buster (ダブルキン肉バスター) Used as the deciding move during the fight with . Kinnikuman does a Neo Kinniku Buster followed by a standard Buster while he and his opponent descend towards the ring.
- Side Kinniku Buster (サイドキン肉バスター) Used during the fight with . Kinnikuman grabs his opponent in a standard Buster hold and jumps onto the ropes. He then launches himself sideways, landing on the wall.
- Muscle Docking (マッスル・ドッキング) A tag technique first used during the fight with The 4D Killer Combo. Kinnikuman and his partner Kinnikuman Great. Later Him and Terryman durring the fight with the Hell Missionaries. They each take an opponent. While one performs a Kinniku Buster on his foe, the other performs a Kinniku Driver on his. With the one performing the Buster descending and the one performing the Driver ascending, they "dock" when the Buster performer sits on the other's shoulders. They then drive into the canvas, affecting both opponents.
- Buster Variation Part 5 (バスターバリエーションPART5) Used by Kinnikuman and on during the fight with the Hell Missionaries. Kinnikuman and Terry grab one opponent and simultaneously perform a Kinniku Buster on him, both grabbing one side.
- Kinniku Driver (キン肉ドライバー, Kinniku Driver), First used during the fight with . Kinnikuman runs up to his opponent and places his head between their legs. He then leaps up, flips the opponent upside down, places his feet on the underside of their arms, and drives them into the canvas.
- Muscle Spark (マッスルスパーク, Muscle Spark), Kinnikuman ultimate technique and one of the Kinniku Clan's Three Great Techniques. Kinnikuman bounces his opponent off his chest and into the air numerous times. He then leaps up after them and gets behind them. He then grabs their wrists with his hands, their neck with his right leg, and their left leg with his left leg, and pulls. As they descend, he gets back-to-back with his opponent and grabs their arms and hooks their legs with his. Right before they hit the canvas, he arches his back causing his opponent's body to fold, and drives them neck and knees first into the canvas.
- Fu Rin Ka Zan (風林火山, Fu Rin Ka Zan) Used as the deciding move during the fight with . It is a four-part maneuver: (風 Fū, "Quick Like the Wind"): Kinnikuman first puts his opponent in a double underhook hold, spins him around, throwing him from arm to arm, and slams him into the canvas . (林 Rin, "Silent Like the Forest"): Rolling Cradle. He then grabs his opponent under his arm and jumps into the air, flipping himself and the victim around until he has him in a piledriver hold. (火 Ka, "Conquer Like the Fire"): With his opponent in a hold, Kinnikuman drives him into the canvas . (山 Zan, "Immovable Like the Mountain"): Finally, he throws his opponent into the air, jumps up after him, catches him in a Reverse , and falls back to the canvas .