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Iaian (イアイアン, Iaian; Viz: Iairon) is the A-Class Rank 2 professional hero of the Hero Association and the top disciple of Atomic Samurai.


Iaian with helmet

Iaian with his helmet

Iaian is a young man with short blonde hair and blue eyes. He wears a long-sleeved black shirt under his sleeveless medieval iron armor with a shoulder pad on his left shoulder. In his first appearance, he also sported a matching medieval iron helmet. He carries his sword on his left hip. After his fight with Melzargard, he lost his left arm.


Iaian is shown to be quick-tempered as witnessing the widespread destruction of A-City, an act he deems "unforgivable," enrages him. Also, upon being attacked by a mysterious alien, Iaian gives no quarter and responds immediately with an attack of his own. He is quite headstrong and cocky since he was willing to take on Garou head-on to make his master proud of him without regarding his strength, although this could also be interpreted as a deep desire to make his master proud of him.

Iaian is described to be persistent in battle, refusing to back down regardless of whether his enemy is more skilled.[1]This is likely the reason Atomic Samurai constantly interrupts his battles against opponents like Rhino Wrestler and Melzargard. Despite his persistence, he is in fact very analytical in battle, determining the strength of his opponent and all of their abilities. He also does not underestimate his opponent, and constantly warns his two comrades to be on-guard.


Warning The following section contains Webcomic spoilers. You have been warned, manga-only readers.

As a disciple of Kamikaze, Iaian was recruited after an apple cutting test. As Kamikaze has the ability to tell how a person lived their life by cutting with a sword, he only recruits disciples if they pass his test. At some point in the past he and his teammates fought Child Emperor and lost.


Hero Association SagaEdit

Alien Conquerors ArcEdit


Iaian dodging an attack and losing his arm

After the destruction of A-City, Iaian climbs out of the rubble only to see nothing standing in front of him but the Hero Association's Headquarters. He later saves a father and his son from being killed by Melzargard after the father moves some rubble to get to his son.[2] As he is standing there, the monster appears behind him and attempts to crush his head. Melzargard only crushes his helmet, its occupant having moved away in time. He states that there was no way he would not have noticed its killing intent and proceeds to attack the monster.[3] While dodging one of the monster's attacks, his left arm was torn off. Melzargard then began splitting itself into five different forms. [4] Feeling hopeless of his situation, the monster is suddenly cut to pieces by Atomic Samurai and Iaian was ordered to stop bleeding by his master. [5]


Iaian surprised to see Silver Fang alive

While the S-Class heroes are fighting the monster, Iaian advised them to retreat and find another way to kill the monster, but his pleas were futile.[6] During the fight he witnessed Silver Fang being struck by Melzargard's attack and was surprised to see he was unharmed.[7] After the monster was defeated, the spaceship that was above them began to collapse and Iaian was helped carried by Atomic Samurai.[8]

Human Monster SagaEdit

Super Fight ArcEdit

Iaian, Okamaitachi and Bushidrill are waiting outside discussing about Garou's hero hunt, while their master Atomic Samurai is attending a meeting with the Council of Swordmasters.[9] After Atomic Samurai killed the monsterized Haragiri, Iaian noticed the smell of blood and Atomic Samurai ordered they will strike the Monster Association.[10]

Monster Association ArcEdit

Iaian is seen waiting for the S-Class meeting to end with his fellow disciples.[11]

Iaian Rhino Wrestler

Iaian stops Rhino Wrestler's charge

Iaian is one of the heroes who fights the first wave of monsters from the Monster Association.[12] When Rhino Wrestler appears from the 2nd wave, Iaian watches the other heroes attempt to attack the monster but fail miserably.

The A-class hero unsheathes his sword and strikes his horn, momentarily halting the monster's movement.

Rhino Wrestler rates his attack 69 points, and the others see it as the opportune moment to strike together. First, Jet Nice Guy attacks with his Ultimate Jet Straight across the monster's face; next, Double Hole tickles his nose to activate his energy sneeze. Crescent Eyebroll uses his Crescent Consecutive Slashes, while Narcisstoic uses his Rose American Sack attack, and the rest of the heroes join in, but Rhino Wrestler is able to blow all of them away, rating each of their attacks. The heroes are shocked at his power, while Rhino Wrestler reminisces of a moment when Gyoro Gyoro conversed with Rhino Wrestler before the monster raid and how Gyoro Gyoro commended the monster for the increase in strength. Rhino Wrestler screams out for the strongest heroes to fight him, all-the-while fighting Iaian. Rhino Wrestler is able to hold Iaian back, but before the battle could continue further, Atomic Samurai tells his disciple he would take his place. Iaian insists he could handle it, but Atomic Samurai tells him he would cut off his horn himself.

Iaian, Bushidrill, Okamaitachi enters the Monster Association HQ.

Iaian, Bushidrill, Okamaitachi encounter Do-S and the mind-controlled mercenaries. They do battle but are interrupted by Sweet Mask. Sweet Mask calls for the swordsmen to leave the battle to him. They leave and encounter Pig God eating The Great Food Tub and decide to take another route.[13]

The sword heroes encounter Devil Long Hair, and Okamaitachi becomes infatuated with him. Iaian and Bushidrill realize Okamaitachi is infatuated with the monster. Bushidrill and Iaian tell Okamaitachi to snap out of it, reminding them that their role is to lighten their master's burden. Okamaitachi attacks with his Air Blade, but Devil Long Hair stops it with his hair, shocking the swordsmen. Devil Long Hair counterattacks, but Bushidrill manages to stop the attack before any harm was done. The demon-level monster then extends his hair toward Iaian and Bushidrill, and the swordsmen prepare for battle.[14]

Warning The following section contains Webcomic spoilers. You have been warned, manga-only readers.

The three swordsmen work as a unit, rushing in and cutting Devil Long Hair's hair as fast and as effectively as possible, and manage to defeat him, although they admit it was a difficult opponent, and had they not worked together, they surely would have lost. But Okamaitachi, Iaian, and Bushidrill are attacked by Evil Natural Water, a Dragon-level monster, who defeats all of them and badly injures them, knocking Okamaitachi and Bushidrill unconscious. Child Emperor comes across them, and Iaian, the only one who is still conscious, urges Child Emperor to leave, as the monster is still lurking around. 

The three swordsmen are then swallowed up by Pig God, who found them and consumed them, and manages to bring all three of them up to the surface and regurgitate them without any noticeable injuries. As Atomic Samurai watches the other S-class heroes fighting and being unable to do anything since he lost his sword, Iaian speaks to his master and gives him his sword to fight Garou. 

Appearances in Other MediaEdit


The Murder Case That Is Too ImpossibleEdit

Heroes in spring

Iaian in the hot spring

Iaian was invited along with the S-Class heroes to a hot spring resort, after the Dark Matter Thieves failed invasion. While enjoying himself at the hot spring, he wasn't satisfied that some of the heroes that did not participate in the battle were invited to the resort, but Bang managed to calm down the situation. The next day after the ceremony, the heroes find Zombieman murdered, stabbed in the back by Atomic Samurai's katana.

Atomic Samurai alibi

Iaian at the banquet with the other heroes

As Child Emperor interrogates every hero, Iaian was one of many alibis for Atomic Samurai so all suspicions were dropped. While the investigation wasn't progressing, Tatsumaki tried to restrain everyone, until Zombieman suddenly woke up. Zombieman later revealed that Atomic Samurai's katana was floating with green light surrounding it similar to Tatsumaki when it stabbed him. Zombieman didn't care about what happened the night prior and the heroes disbanded.[15]

Abilities and PowersEdit

As a top ranking A-Class hero, he is an extremely skilled and powerful fighter. According to Fubuki, he like his fellow disciples, could be S-Class if it wasn't for Sweet Mask. It is worth noting that while he was weakened after losing his arm, he still remains a strong combatant.

Physical AbilitiesEdit

Immense Speed and Reflexes: Iaian is shown to possess outstanding speed and reaction time, as he was able narrowly avoid a sneak from Melzargard from behind along with dealing a counterattack simultaneously and managed to hold his own against him for a while. He also dodged a follow-up attack from the alien at close range, though not completely, as he lost his left forearm from it. He is also capable of performing several slashes within a second.[1] He is fast enough to cut a wave of bullets while slicing Tongara's rail gun in seconds.

Immense Strength: Iaian was strong enough to stop the charge from Rhino Wrestler, a Demon level monster. Something that even a group of A-Class and B-Class heroes together were not able to do. Rhino Wrestler even acknowledged the strike to his horn, rating it a 69/100, which is much higher than what he rated the other heroes' attacks. He was also strong enough to slice The Organization's rail gun and damage their highly durable armor being used by Tongara.

Immense Endurance: Iaian is very durable with high pain tolerance, as he only displayed shock and no signs of outward pain from having his left forearm blasted off from Melzargard's attack.

Enhanced Senses: Iaian can sense murderous intent around him, and can strike without needing to open his eyes.

Fighting StyleEdit

Expert Swordsman: Being the top disciple of Atomic Samurai, Iaian is extremely skilled with the sword. He has been shown to have a rather keen grasp of what is happening around him, easily avoiding an attack from a large monster and then returning a strike right after.

  • Iai of Certain Kill (必殺の居合, Hissatsu no Iai): True to his name, Iaian attacks with iai strikes, unsheathing his sword, performing slashing attacks, and returning the sword to his sheath all in an instant. Each slash aims for the enemy's vitals and can be performed all under a second. Among the three disciples of Atomic Samauri, Iaian has the fastest swordplay.[1]


Katana: Iaian carries a katana that has a black hilt with a circular hand-guard. The sheath is painted black.

Knight Armor: Despite studying swordsmanship under Atomic Samurai, he dons an iron knight-like armor instead. During the invasion of the Dark Matter Thieves, the helmet was crushed by Melzargard's sneak attack. His armor was made by a famous blacksmith.[1]

Hero RatingEdit

Iaian's rating determined by the Hero Association:[1]

Ability Type Stamina Intelligence Justice Endurance Power Popularity Effectiveness Fighting Ability Total

Major BattlesEdit

Participants Chapter(s) Episode(s) Result
Iaian vs. Melzargard 31, 32 10 Interrupted by Atomic Samurai
Heroes vs. Rhino Wrestler 94 None Interrupted by Atomic Samurai
Iaian, Okamaitachi and Bushidrill vs. Do-S and Narinki's Private Squad 102 None Interrupted by Sweet Mask
Iaian, Okamaitachi and Bushidrill vs. Devil Long Hair 104, 110 None Win
Iaian, Okamaitachi and Bushidrill vs. Evil Natural Water 114 None Ongoing
Warning The following section contains Webcomic spoilers. You have been warned, manga-only readers.
Participants Chapter(s) Episode(s) Result
Iaian, Okamaitachi and Bushidrill vs. Child Emperor (Mentioned - Off screen) None None Loss


  • Iaian's name is a Japanese portmanteau of "Iai" (居合い), a sword-based Japanese martial art, and "iron" (アイアン), referring to his armored appearance.
  • Iaian without armor.[16]
  • According to the databook:
    • What he likes are his master, his blacksmith, his favorite armor shop, and watermelon.[1]
    • What he dislikes are people who put a damper on conversations, demonstrating iai on TV.[1]
    • His hobbies are choosing swords, travel, golf, and visiting temples and shrines.[1]
  • The origin of his hero name comes from his unrivaled skill at Iaido (居合) and his iron armor.[1]
  • There appears to be a habit in the series of Iaian's fights being interrupted, as seen with his battle against Melzargard, Rhino Wrestler, and Do-S.


  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 One-Punch Man Encyclopedia; One-Punch Man: Hero Perfection, page 28-29
  2. One-Punch Man Anime; Episode 10
  3. One-Punch Man Manga; Chapter 31, page 7-12
  4. One-Punch Man Manga; Chapter 31, page 22-27
  5. One-Punch Man Manga; Chapter 32, page 2-7
  6. One-Punch Man Manga; Chapter 33, page 3-4
  7. One-Punch Man Manga; Chapter 34, page 11-16
  8. One-Punch Man Manga; Chapter 36, page 3-4
  9. One-Punch Man Manga; Chapter 69, page 2-6
  10. One-Punch Man Manga; Chapter 69, page 25-27
  11. One-Punch Man Manga; Chapter 93, page 17
  12. One-Punch Man Manga; Chapter 94
  13. One-Punch Man Manga; Chapter 102
  14. One-Punch Man Manga; Chapter 104
  15. One-Punch Man OVA; The Murder Case That Is Too Impossible


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