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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 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. During his fight with Melzargard, he lost his left arm.[2]


Iaian is shown to be quick-tempered as witnessing the widespread destruction of A-City, an act he deems "unforgivable," enrages him.[2] Also, upon being attacked by a mysterious alien, Iaian gives no quarter and responds immediately with an attack of his own.[2] 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,[3] although this can 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 stronger or more skilled.[1] This is likely the reason Atomic Samurai constantly interrupts his battles against opponents like Rhino Wrestler,[4] and Melzargard.[2] 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, Bushidrill and Okamaitachi, to be on-guard.

As a seasoned warrior, Iaian is also quite perceptive in and out of battle. Namely in regards to understanding the mindset of others around him. Having picked up on Sweet Mask's bloodthirst from when the A-Class hero slaughtered the leftovers from the alien invasion. He made the snap decision to double back and prevent another massacre at the hands of the idol and save the brainwashed mercenaries.[5] Being the cool and collected type; instead of getting into a heated debate, Iaian suggests to Okamaitachi that they run a thorough background check on the superstar afterward.

Abilities and Powers[]

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

Physical Abilities[]

Iaian dodges Melzalgard's sneak attack

Immense Speed and Reflexes: Iaian is shown to possess outstanding speed and reaction time, as he was able to narrowly avoid a sneak attack from Melzargard from behind along with dealing a counter-attack shortly afterward and managed to hold his own against the monster for a while.[2] He also dodged a follow-up attack from the alien at close range, though not completely, as he lost his left forearm from it.[2] He is also capable of performing multiple slashes within a second, and is fast enough to speed past and cut a wave of bullets while slicing Tongara's rail gun into pieces in the blink of an eye.[6] Iaian's amazing speed was once again shown when he was able to intercept Sweet Mask's attack that intended to decapitate the entire Narinki's Private Squad with the speed somewhat surprising the handsome hero.[7]

Iaian stops the charge of Rhino Wrestler

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.[8] Rhino Wrestler even acknowledged the strike to his horn, rating it a 69 out of 100, which is much higher than what he rated the other heroes' attacks.[9] He was also strong enough to slice The Organization's rail gun and damage their highly durable armor being used by Tongara.[10] Additionally, Iaian was capable of slicing through Tatsumaki's psychic barrier which she created to shield him from the destruction of the Monster Association HQ.[11]

Enhanced Endurance: Iaian has a 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.[2] He was also the only one out of the three disciples who could still fight along with the rest of the heroes against the Monster Association cadres, despite having just beaten by one of the latter.

Enhanced Senses: Iaian can sense murderous intent around him, and can strike without needing to open his eyes.[12]

Fighting Style[]

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 Rating[]

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

Ability Type Stamina Intelligence Justice Endurance Power Popularity Effectiveness Fighting Ability Total
Weapons 7 5 7 6 7 6 6 8 52


A sketch of Iaian in a hot spring, showing the metal band around the base of his amputated arm.

  • 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.
  • Murata drew a sketch of Iaian without armor.[13]
  • 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 battles 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 One-Punch Man Encyclopedia; One-Punch Man: Hero Encyclopedia, page 28-29
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 One-Punch Man Manga and Anime; Chapter 32, and Episode 10
  3. One-Punch Man Manga and Anime; Chapter 69, and Episode 19
  4. One-Punch Man Manga; Chapter 97
  5. One-Punch Man Manga; Chapter 105, page 14
  6. One-Punch Man Manga; Chapter 105, page 8-10
  7. One-Punch Man Manga; Chapter 106, page 7-8
  8. One-Punch Man Manga; Chapter 96, page 108-109
  9. One-Punch Man Manga; Chapter 96, page 110
  10. One-Punch Man Manga; Chapter 105, page 10
  11. One-Punch Man Manga; Chapter 130 (Online), page 7
  12. One-Punch Man Manga; Chapter 107, page 27-28


Hero Association
S-Class 1. Blast • 2. Tornado of Terror/Tatsumaki • 3. Silver Fang/Bang • 4. Atomic Samurai/Kamikaze • 5. Child Emperor • 6. Metal Knight/Bofoi • 7. King • 8. Zombieman • 9. Drive Knight • 10. Pig God • 11. Superalloy Darkshine • 12. Watchdog Man • 13. Flashy Flash • 14. Demon Cyborg/Genos • 15. Metal Bat/Bad • 16. Tanktop Master (Tank Topper Army) • 17. Puri-Puri Prisoner
B-Class 1. Blizzard of Hell/Fubuki (The Blizzard Group) • 2. Eyelashes • 3. Mountain Ape • 6. Wild Horn • 7. Caped Baldy/Saitama • 20. Glasses • 25. Pink Hornet • 29. Double Hole • 39. Smell Master • 39. Reclusamurai • 43. Gun Gun • 49. Butcher • 50. Jet Nice Guy • 60. Needle Star • 65. Piko • 69. Crying Man • 70. Trap Tengu • 71. Captain Mizuki/Mizuki • 74. Lily of the Three Section Staff/Lily • 77. Bone • 81. Tanktop Black Hole • 93. Mushroom • 99. ShooterDarkness BladePineapple
Undetermined Class GunmaTanktop GirlTanktop RockabillyTanktop RacerTanktop Al DenteTanktop SwimmerTanktop JungleTanktop MaskTanktop HatterTanktop DoctorPandaman
Staff Members AgoniBushoC Branch OperatorConsole OperatorExmaGuichesJinzurenMain Branch OperatorMcCoyNarinkiSekingarShelter Nr. 7 GirlSitchSome Important GuySpecial Committee GirlZ Branch Committee GirlZ Branch OperatorZeimeet