Koyama has a rugged and thuggish appearance. He has a light brown mohawk mirrored by a goatee, a diagonal scar across the centre of his face, a lip ring, three earrings in each ear, and a blatant lack of eyebrows. He is normally seen wearing a hoodie with a black tank top underneath, along with black leather pants and boots.
After Claw is defeated once and for all, Koyama removes his piercings and goatee, and has grown his hair out again. His hair is also black, though it's unknown if it's dyed or if it's his natural hair colour. Like the other Scars, his scars inflicted on him by Suzuki miraculously disappear as well.
Koyama is prideful, reckless and easily frustrated. He has no qualms about using violence against kids and is a self-proclaimed "asshole", who will brutalize even opponents who willingly submit to him. After witnessing bullies attack Ritsu and force Shigeo to apologize for him, Koyama sadistically forces the bullies to grovel and apologize to him to replay the scene that happened just before. It's possible that this is his ruthless way of making others learn to never do evil, at least in regards to commoners. He is prideful, and insists that he did not "lose" against Mob, even though he fled the scene rather than risking facing him after discovering how powerful he was. He is willing to fight dirty, using cheap shots and knockout gas to try and defeat opponents that his sheer power can't overwhelm.
He showcases being naive from time to time, and often overlooks things or tries to avoid the scenario that's too difficult for him.
However, later on his personality changes to reveal that he's willing enough to work with old enemies against a common opponent and is no longer as prideful as he once was before.
In chapter 100.7, it is revealed that he finally got his act together. He became a more honest worker, prioritizing his customer's satisfaction over the profits of the store, much to Sakurai's disapproval. Also, for the sake of protecting their jobs, Koyama is willing to fight against ???% Mob unlike before and working together with Sakurai instead of being hardheaded in fighting alone to prove his worth.
Big Cleanup Arc
Koyama was first seen when he was assigned by Claw to capture Mob but ended up mistakenly targeting Ritsu, attacking him during a scuffle between middle schools in an alley. When he got his hands on Ritsu, Mob intervened and the two had a brutal battle where Mob ended up going 100% Animosity due to Koyama's callous and violent treatment of Ritsu and the other students. Koyama sustained heavy damage in the beatdown that ensued. Before Mob could defeat him, however, he used Sakurai's cursed perfume to put him to sleep, then quickly escaped with Ritsu.
7th Division Arc
Later, he encountered Mob at the base of Claw's 7th Division, standing in their way. Mob, more ready this time, instigated a completely one-sided battle in which Koyama was quickly thrashed and defeated.
World Domination Arc
Weeks later, Koyama reappears in a car with Sakurai to recruit Mob to help fight Claw's plan to take over Seasoning City. After Koyama assures Mob they have no intent of harming him and they don't know what happened to his family, Mob suddenly lifts the car and declares he's about to get out. They convince Mob to stay when they mention that Reigen and some other friends are waiting for them at the Awakening Lab. Mob impatiently levitates the car to avoid traffic, making Koyama feel nauseous. He berates Mob for being reckless but Sakurai says that at least they will be able to shake off possible pursuers. He is then present with the others at the briefing meeting.
Koyama is part of the group that is sent to infiltrate the Claw-occupied Culture Tower via the sewer. Their progress is halted when Shimazaki appears, who pummels them all and forces them to retreat.
Koyama later appears with Teruki and the rest of Scar to back up Ritsu when he's cornered, again by Shimazaki. Koyama is the first one able to land a hit, throwing a manhole cover at him while he's distracted. Teru and Scar all attack Shimazaki at the same time, but are overwhelmed by his incredible power. Shimazaki explains that Scar was the rank of those marked for failure rather than of Claw's advanced, enraging Koyama. Eventually Teru figures out how to predict Shimazaki's teleportation and they gain the upper hand for a moment, even being able to land some powerful hits. However, Shimazaki awakens his ultimate ability, Mind's Eye, and quickly defeats them all in a second. Thankfully, Shimazaki is defeated by a passing Reigen and the battle ends. Koyama plans on attacking the Culture Tower with Mob, but he forces them all to wait and recover from their fight with Shimazaki. He later watches with the rest of the heroes as Mob battles Suzuki atop the Culture Tower.
Koyama is seen talking with Sakurai after the incident has come to a close, asking what he'll do without Claw or the Scars around anymore. He is later seen to have been hired at Smile Mart alongside Sakurai.
Noticing the chaos caused by Mob's ???% mode, Koyama and Sakurai exit Smile Mart and attempt to protect their shop. They're both shocked to realize it's Mob who's responsible, and fail to defend the shop from his immense power. They stand down and leave the area once Suzuki arrives via airdrop, shocked by their old boss' reappearance.
Powers & Abilities
Koyama specializes in using his psychic powers in conjunction with brutal hand-to-hand combat, enhancing his blows using telekinesis. He is also capable of summoning defensive barriers like most psychics. He is shown to be a skilled fighter even when not using any psychic techniques as well. By his own estimation he considers himself stronger then Terada. His psychic aura takes on a reddish color with a purple border around the edges.
Koyama concentrates and creates bands of psychic energy that wrap around his arms and lead into his fists. This is a passive technique that once activated allows him to penetrate psychic barriers with physical strikes and deal heinous amounts of damage. He normally removes his hoodie before activating this ability.
A sub-technique of Telekinetic Helix, Koyama concentrates and revolves his psychic energy around his arm and then attacks with a strong lariat into the target's stomach. He described this as his trump card, though it failed to do much against Mob in his 100% Animosity state besides knock him back and destroy his school uniform.
Notes & Trivia
- He almost threw up when Shigeo made his and Sakurai's car fly, suggesting he may suffer from motion sickness.
- Oddly enough, his name is an oxymoron to his personality (Megumu meaning 'kindness' to his 'asshole' behaviour, although this seemed to have changed recently).
- "Hey you, good-for-nothing. What's with that rebellious stare? ... Grovel, and apologize to me. We're reviewing the scene you were playing out earlier. I know! All of you should grovel! Will this make you a little more willing? If you don't grovel, I'll kill all of you."
- "That's a wise decision, but I'm an asshole."
- Mob Psycho 100 Manga — Vol. 4 Chapters 30–33.
- Mob Psycho 100 Manga and Anime — Vol. 5 Chapter 38 (page 10-16) and Episode 9.
- Mob Psycho 100 Manga — Vol. 5 Chapter 35 (page 4).
- Mob Psycho 100 Manga and Anime — Vol. 4 Chapter 32 (page 8) and Episode 8.
- Mob Psycho 100 Manga and Anime — Vol. 4 Chapter 32 (page 11) and Episode 8.
- Mob Psycho 100 Manga and Anime — Vol. 4 Chapter 33 (page 10) and Episode 8.