- Classification: Jikan Choujin
- Homeland: Avenir Kingdom, Planet Avenir (raised in Hachiouji, Tokyo, Japan)
- Age: 13~14
- Height: 183 cm
- Weight: 94 kg
- Choujin Kyoudo: Unknown
- Trademark Techniques: W Kinniku Buster, Chaos Sphere Bottom
- Tag Teams: Muscle Brothers Nouveau (Mantarou Kinniku)
- Submitted by: Megumi Kaneda (兼田恵) of Kanagawa and Ōshaku Yoshida (吉田大錫) of Osaka
- First Appearance: Manga (Part 2) Chapter 25
Chaos is a very kind, although somewhat childish, character. Though he claims to be a human and not a Choujin, as a child a horn grew on the side of his head. Currently the horn is gone and in its place is a keyhole shaped hole, a characteristic shared with the Jikan Choujin (he also has a design pattern on his body similar to them). In addition, when the Jikan Choujins used their "Legend" Destroying Bell, he suffered along with the other choujin. He is the lone survivor of the massacre of his parents and fellow villagers. Remembering this incident causes him to go into violent fits, at which point he has to take a sedative (in the form of an asthma inhaler). During these fits, his fighting strength increases many fold, and he is able to compete at the same level as Neptuneman. After taking his medication, however, he forgets everything he did during his fit.
Chaos is a huge Choujin Otaku, and has a huge collection of Choujin-based goods (including Kinkeshi figurines). He will go through any means to add to his collection, even beat up his friend Kawazaki-kun. He also has an odd obsession with pigs and giving people pig-themed gifts, most probably due to the fact that his earliest clear memory is living with a huge pig.
He works as a bogus Choujin Wrestler named Butanikuman (ブタ肉マン, Porkman), putting the money he earns into the Gakincho House orphanage he grew up in. Although Chaos seems to have feelings for Rinko, he has a huge crush on singer Matsuda Seiko and has a collection of her merchandise. He appears to greatly admire Idol Choujin Geronimo as a fellow "human fighting alongside Choujins".
He refers to himself in the first person as Wachiki (ワチキ), occasionally using the more common Boku (ボク). He also refers to Sister as Mother (マザー).
- W Kinniku Buster
- Chaos Sphere Bottom
- King German Suplex
- Rolling Savate
- German Suplex
- Muscle Docking (failed)
Chaos grew up on Planet Avenir and was trained by his father in Choujin Wrestling. Two mysterious figures attacked his village and killed everyone but him. After he escaped, he returned to his parent's graves and promised to avenge them someday and allow the Avenir Clan to live on.
He somehow loses his memories, comes to Earth, and is found by Sister resting underneath a huge pig. The pig looked at Sister and then walked into the woods, never to be seen again. Sister then took Chaos to Gakincho House and raised him as her own. Over the years he got stronger and also helped Sister raise the orphans, whom love him dearly and refer to him as An-chan (あんちゃん, Big brother).
He uses his Choujin otaku knowledge to his advantage and gets a job with a bogus Choujin Wrestling show as Butanikuman. Whatever money earned he doesn't spend on his Choujin goods collection he spends on gifts and food for the orphens. In 1983, he and his friend Kawazaki-kun attend the Universal Choujin Tag Tournament (the Dream Choujin Tag Arc). After Neptuneman flew into space to blow himself up, Chaos manages to obtain the Kinnikuman Great mask. Kawazaki-kun is actually the first to grab the mask, but Chaos smacks him around until he gives it up.
Chaos's future is so far unclear. During a time period known as the Justice Rest (正義の安息（ジャスティス・レスト）), where legends like Kinnikuman, Terryman, and Robin Mask were raising their children and others like Ramenman, Buffaloman, and Brocken Jr. were settling into retirement, a wave of Akugyo Choujin seized the opportunity and attacked Earth. In the Choujin Encyclopedia (超人大全, Choujin Taizen) this incident is referred to as the Rain of Brutality (残虐の雨, Zangyaku no Ame). They were defeated by a lone Seigi Choujin whose name is unknown to Meat and Mantarou (due to Mantarou ripping the Encyclopedia page out and using it as toilet paper before Meat could read his name).
Although Mantarou is very sure that this man is Chaos, Meat and Chaos himself are skeptical. Furthermore, before the timeship Kevin Mask can take off, Mantarou is sent out to remove a headstone that is blocking it's path. The first letters in the name on the headstone are covered in dirt, but the last two letters are "ΘS".
Ultimate Choujin Tag Arc
Chaos meets Mantaro and the others during one of his bogus Choujin Wrestling performances, during which he accidentally begins fighting for real after a pair of brass knuckles hitNinkaido Rinko Rinko Ninkaido. He is ganged up on by the other wrestlers until Mantaro saves him and they are chased out of the show by angry fans. He brings them back to the Gachinko House, where they see his huge Choujin Goods collection, which includes the Great Mask. Mantarou asks Chaos to pose as Kinnikuman Great and team up with him, but he refuses because he is actually a regular human. However, he changes his mind after Rinko dresses up like Seiko Matsuda and dances around for him.
As they enter for the preliminary Battle Royal, Chaos does many comical otaku-type things, such as filming a bootleg of the match, asking for autographs from all of the Choujin, and making a face print of Mongolman's face make-up. During the match, Mantarou tries his best not to tag Chaos in so as to protect him, but after Neptuneman and Seiuchin begin fighting Chaos is forced into the action. He is at first outpowered, but after he realizes that he is bleeding, he becomes empowered through one of his episodes and begins fighting back. After he takes his medicine and calms down though, he is easily put in the Optical Fiber Cross Bomber, but is saved when Mantarou throws Seiuchin's head cover in the path of the technique.
After overhearing Meat tell Mantarou that teaming up with Chaos wasn't the best idea, Chaos runs away. However, after Sister helps him realize that the "key" to unlocking his memory is courage, he understands that he must go back and complete the tournament. Although Ikemen has to take his place during the lottery drawing, he makes it back in time for the first match. During their match against the Hell's Carpentors, his otaku knowledge helps them defeat PlaMoman's plastic model techniques, but his inexperience against Choujins causes many problems and he soon goes into another one of his fits. They try to win with the Muscle Docking, but Chaos becomes too scared to complete it, forcing Mantarou to defeat Deiku Toryu with a Muscle G. With support from Mantarou, Rinko, Sister, and the others, he is finally able to defeat PlaMoman with a Power Bomb, earning a victory for the Muscle Brothers Nouveau. Afterwards, the four competitors become friends.
Chaos is later seen watching the Reserve Match between the Five Disastors and the Handblades. He reveals that he greatly admires Geronimo, both being humans who fought alongside the Seigi Choujins. Chaos later trains alone in the rain, until Rinko arrives with his old friends from the Bogus Choujin Wrestling Show. Recently, Chaos was greatly surprised to learn that Mari Nikaido was Rinko's mother.
The Muscle Brothers Nouveau are currently fighting the 20 Million Powers in an Electric Cage Match. Because they are a newly formed team, they have yet to master the timing of their combo attacks and are soon overpowered by the 20 Million Powers. Recently, Chaos' memories have been restored and his aura tore apart the Great Mask and costume. He unleashed a series of attacks on Buffaloman proving he is more the he appears to be. During the fight the 20 Million Powers used the Long horn train but, they countered also using the Long Horn Train using Chaos's legs as the horns. It caught the 20 Million Powers off guard then Chaos puts the Japanese leg roll on Mongolman, while Mantaro puts Buffaloman in the Muscle G making their new move the Muscle Evolution. The move defeats the duo and destroys the Mongol Mask.
- Alias: Butanikuman, Kinnikuman Great III
- Least Favorite Food: Beni shoga
- Favorite Celebrity: Seiko Matsuda
- Saviour of the Interval (間隙の救世主, Kangeki no Kyuuseishu)
- The Man who Creates Legends (伝説を作り出す男, Densetsu wo Tsukuridasu Otoko)
- Saviour of the Era (時代の救世主, Jidai no Kyuuseishu)
- Win/Loss Record (Singles)
- O Minutes Avenir (King German Suplex)
- O Itto Mask, Robin Mouse (W Kinniku Buster)
- Win/Loss Record (Tag)
- Kinnikuman Manias (Mantarou Kinniku)
- O Beefman, Curry Lou Thesz, Faux Lupin (Arm Hook Double Dropkick)
- O Tenmusuman (Double Brainbuster)
- O Itto Mask (Unnamed Combo Technique)
- Muscle Brothers Nouveau (Mantarou Kinniku)