Monjirō Oniyama
Monjiro Oniyama
Kanji 鬼山 紋次郎
Rōmaji Oniyama Monjirō
Alias Onimon
Birthdate Unknown
Age 17–18
Gender Male
Race Humans
Hair color Black
Eye color Gray
Blood type O[1]
Abilities Kick dirt and turn it into iron balls
Misc. Information
Manga debut The Brave Warrior Appears?!
Anime debut Fair and Square! The Law of Onimon
Japanese voice actor Katsuyuki Konishi
English voice actor Randy Brososky

Monjirō Oniyama (鬼山 紋次郎, Oniyama Monjirō), also called Onimon, is a power user who can turn dirt into iron balls. He has 299 talents and believes that fights should always be "fair and square". He also teaches Kōsuke Ueki some new battle techniques to fight Kageo of the Robert's Ten.


Although he appears to be an adult, Oniyama is only a third year student at Doinaka Middle School. Portrayed as a young muscular man of average height, he has messy black hair that reaches almost to his shoulders. His eyebrows are thin and his eyes are sharp yet carefree, partially covered by the hair that falls over his head. The lower part of his face is shown to have some sparse stubble and a growing mustache. His skin has a tanned shade to it and he also has his left ear pierced with three earrings. Oniyama's outfit and appearance is very casual. He sports a purple shirt that is left unbuttoned and collar left up, along with pale khaki pants with black stripes on both sides, secured by a simple brown buckle. He wears brown shoes and carries a black sling bag with him on his first appearance.[1]

In contrast to his appearance, Oniyama is a strong,[1] kind man with a laid-back personality and believes that the fights should always be "fair and square", with no foul-play.[1] He is first introduced when Fukusuke Hibiki is about to be beaten up by a group of thuds.[2] Oniyama knocks them all out, but instead of leaving them there, tends to their injuries.[2] He acts in a similar way towards Ueki after their match as well, which shows that he is caring at heart. His caring side is also visible from his feelings towards his hometown, which he wishes to rejuvenate through the talent to boost the village economy.[3] In fact, it is the reason that he joined the tournament.[3] He is shown to get bored easily, leading him to announce that "[it's] a drag".[3] Following his match with Ueki, he learns that it is not the number of talents one has, but the strength of one's beliefs that matters.[4] Later on, he teaches Ueki some new battle tricks that would help the latter defeat Kageo Kuroki of the Robert's Ten.[4]


Monjirō Oniyama hails from a sparsely populated village, which is almost at the verge of being deserted. Saddened by their village's decline, he and his friends decide to give their best to rebuild the village and bring it back to life. However, by the time they reach middle school, his friends decide to move to the city as soon as they graduate, like everyone else did. When an enraged Oniyama asks if they have forgotten the promise they had made, they reply it was a long time ago and moreover, they have even heard that the school will be closed down after they graduate. That evening, Oniyama heads back home disheartened and promises that he will never abandon his village. Suddenly, he hears someone moaning and turns around to see an old man carrying something heavy on his back collapse from stomach ache.

Oniyama takes the man to the nearby clinic only to see that it has been closed down until further notice. Seeing that there is no other choice, he takes him to the town hospital where the doctor examines him and tells him he is okay. When Oniyama asks if he could take him back the morning next day, the doctor says he can't as there is not even a doctor in the village, and he has to to be hospitalized for a while. Oniyama tries to persuade the doctor to discharge the old man as he would be alone if he stayed there, but the man says it is okay as he cannot return in that state and become a burden to everyone. That night, Oniyama reflects over what is wrong with the village, and he swears to rejuvenate the village so people would not feel that have to leave for the city. He also takes part in the competition for the same reason, to win the talent to boost the village economy (through the The Talent of Blank).[1]

Battle with UekiEdit

Oniyama first appears while Ueki is getting beaten up by a group of delinquents for trying to question their actions against another boy. When the leader of the gang decides to thrash Ueki one last time, he is attacked by Oniyama's sling bag. Oniyama deems them lame for beating him up as a fight between men should always be fair and square, which also happens to be his personal policy. The thuds decide to gang up on him, irritated by his ignorant attitude, but Oniyama knocks them all out in one go and points his fist at the leader. After they panic and run away, Mori thanks him for saving Ueki, but he leaves saying he cannot stand when hoods gang upon someone rather than fighting them one-on-one, fair and square.

Later on, Mori gets herself a PDA from Yodogawa that alerts her when an enemy power user is nearby. As she tries to get a stylishly dressed Ueki, the PDA goes off, indicating that someone is in the proximity. They follow the directions of the device to confront Oniyama lying beneath a tree in the woods. Mori notices that he has 299 talents, hence tries to dissuade Ueki from getting into a fight. However, Oniyama asks Ueki if he is a power user and when Ueki replies he is, instantly gets into a fight with him. He utilizes his power to kick dirt and turn them into iron balls to knock Ueki out, but tends to his injury and apologizes for being quick, to Mori's surprise. He explains that he did so because sneak attacks are not good as they are not fair and square.

The two resume their battle quickly, and Ueki manages to dodge Oniyama's first ball, but Oniyama charges in and kicks him. Fortunately, Ueki does not lose control and stands up and attacks Oniyama. Despite his numerous kicks and hits, Oniyama is not affected as he blocks all of them with fast hands. Yodogawa appears and tells Mori that Ueki is sure to lose this time as Oniyama is much stronger, even stronger than Ueki's previous opponent, Bolo T.. Meanwhile, Oniyama blocks Ueki one last time and hits him again, nearly overpowering him. This prompts Ueki to use his power and he unleashes a tree. Seeing this, Oniyama creates another huge iron ball which slices the tree and progresses towards Ueki and striking Ueki's face. He declares that Ueki cannot win against him because he can never allow himself to lose.

Realization of the truthEdit

Oniyama creates another ball, but Ueki escapes and declares the opponent lame. Enraged, he creates many balls at once, but Ueki creates a bat and hits them all away, towards Oniyama. Oniyama dodges them and charges at Ueki, creating and aiming balls at the sky as he goes. The balls approach Ueki from above and as he looks up, Oniyama creates another set and aims it at Ueki's front. Ueki dodges the latter ones but the former crash on to him. As Oniyama walks away thinking he has won over Ueki, he hears Mori scream and turns around to see Ueki get up. Annoyed by his teasing words again, he sends some more balls towards the sky, one of which falls on Ueki's back. When he asks what is wrong with him wanting to help his village, Ueki replies there is nothing wrong, but relying the the talent of blank for that would become his weakness. Ueki continues by saying that working hard with friends is the way to rejuvenate the village. Oniyama brushes off his advice and dashes in and targets more balls at Ueki, which hit his stomach and face. However, Ueki gets back up and asks Oniyama that since he is 'fair and square', why cannot he rebuild the village without the talent, like a man.

Although Oniyama is shocked to see Ueki endure his attacks, he asks Ueki what he is going to do with the talent of blank and at the same time, creates a spiked ball. When Ueki replies he has not decided yet, Oniyama asks him why he is battling then to which Ueki responds by saying he joined to protect the talent of blank from evil. Ueki produces two trees that surround Oniyama and drop spiky vines at him, but he dodges them. The two begin direct attacks at each other; Ueki dodges Oniyama's ball, creates a tree and misses it intentionally, binding it to a tree. Oniyama, who believes that Ueki took pity on him, yells at him, but Ueki just withdraws the tree he created which leads the tree which was binded to fall right on top of Oniyama. Ueki then answers that he had no pity and that to protect the talent of blank from evil, he will win.

Powers and abilitiesEdit

He has the power to turn earth (dirt) into iron balls by kicking the dirt toward his opponent. He also has 299 talents, and is shown to be strong in hand-to-hand combat that he can fight a group of people with ease.


Kōsuke UekiEdit

He has shown some respect towards Ueki, like attending to his wound when he attacks him without him being ready, and honoring him when they fight. He was mad when he told him he shouldn't use the Talent of Blank on his ideal but after being defeated he stopped his ideal and teached him how to defeat one of the Robert's Ten.

Manga vs. AnimeEdit



  • Oniyama's zodiac sign is Virgo (Libra in the English dub).[1]
  • He has a tendency to abbreviate things quite often.[3]


  1. 1.0 1.1 1.2 1.3 1.4 1.5 Episode 8
  2. 2.0 2.1 Chapter 29
  3. 3.0 3.1 3.2 3.3 Chapter 30
  4. 4.0 4.1 Chapter 32