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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 fairly tall 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.[3] Also, upon being attacked by a mysterious alien, Iaian gives no quarter and responds immediately with an attack of his own.[4] 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,[5] 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,[6] and Melzargard.[7] 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.

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.[8] 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 PowersEdit

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 AbilitiesEdit

Immense Speed and Reflexes: Iaian is shown to possess outstanding speed and reaction time, as he was able to narrowly avoid a sneak from Melzargard from behind along with dealing a counter-attack simultaneously and managed to hold his own against him for a while.[9] He also dodged a follow-up attack from the alien at close range, though not completely, as he lost his left forearm from it.[10] He is also capable of performing several slashes within a second.[1] He is fast enough to speed past and cut a wave of bullets while slicing Tongara's rail gun into pieces in seconds.[11] 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.[12]

Iaian Rhino Wrestler

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.[13] 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.[14] He was also strong enough to slice The Organization's rail gun and damage their highly durable armor being used by Tongara.[15]

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.[16]

Enhanced Senses: Iaian can sense murderous intent around him, and can strike without needing to open his eyes.[17]

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


Iaian stump without shirt

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.[18]
  • 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 1.11 One-Punch Man Encyclopedia; One-Punch Man: Hero Encyclopedia, page 28-29
  2. One-Punch Man Manga; Chapter 31, page 32-33
  3. One-Punch Man Manga and Anime; Chapter 31, and Episode 10
  4. One-Punch Man Manga and Anime; Chapter 31, and Episode 10
  5. One-Punch Man Manga; Chapter 69
  6. One-Punch Man Manga; Chapter 94
  7. One-Punch Man Manga; Chapter 32
  8. One-Punch Man Manga; Chapter 102, page 14
  9. One-Punch Man Manga and Anime; Chapter 31, page 10-12, and Episode 10
  10. One-Punch Man Manga; Chapter 31, page 24-26
  11. One-Punch Man Manga; Chapter 102, page 8-10
  12. One-Punch Man Manga; Chapter 103, page 8
  13. One-Punch Man Manga; Chapter 94, page 105-106
  14. One-Punch Man Manga; Chapter 94, page 107
  15. One-Punch Man Manga; Chapter 102, page 10
  16. One-Punch Man Manga; Chapter 31, page 25-28
  17. One-Punch Man Manga; Chapter 104, page 14


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
A-Class 1. Sweet Mask • 2. Iaian • 3. Okamaitachi • 4. Bushidrill • 5. Heavy Tank Loincloth • 6. Blue Fire • 7. Magic Trick Man • 8. Death Gatling • 9. Tanktop Vegetarian • 10. Stinger • 11. Twin Tail • 13. Great Philosopher • 16. Butterfly DX • 17. Lightning Genji/Genji • 19. Lightning Max/Max • 22. One Shotter • 24. Green • 25. Crescent Eyebroll • 26. Golden Ball • 27. Smile Man • 28. Spring Mustachio • 29. Narcissistoic • 30. Peach Terry • 31. Forte • 32. Shadow Ring • 33. Doll Master • 34. Feather • 35. Air • 36. Chain'n'toad • 37. SneckHeavy Kong
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. Mizuki • 74. Lily of the Three Section Staff/Lily • 77. Bone • 81. Tanktop Black Hole • 93. Mushroom • 99. ShooterDarkness BladePineapple
C-Class 1. Mumen Rider/Satoru • 3. Strange Binding Shell • 13. Tanktop Tiger • 22. D-Pad • 40. Funeral Suspenders • 66. Food Battler Futoshi • 85. Battery Man • 89. Red Muffler • 111. Armored Chief Clerk • 133. Gearsper • 141. Gasmask Cowboy • 174. Grave Eight • 179. Ecolo G • 203. Monocross • 221. Dynamite Man • 225. Angry Man • 283. Horse-Bone • 295. Studless • 300. Poison • 331. Bunbun Man • 347. Hyottoko • 359. Saturn Man • 385. Red NoseMohicanCherion (Soda Pop Boys) • SwimWater GunShoulderpadsHacker NetMeat PounderRabbit
Undetermined Class Tanktop GirlTanktop RockabillyTanktop RacerTanktop Al DenteTanktop SwimmerTanktop JungleTanktop MaskTanktop HatterTanktop DoctorPandaman
Ex-Heroes All Back-ManGrad School GraduateSerial Bomber
Staff Members AgoniBearded WorkerBespectacled WorkerC Branch OperatorConsole OperatorExecutive GirlGuichesMain Branch OperatorMcCoyNarinkiSekingarShelter Nr. 7 GirlSitchSome Important GuySpecial Committee GirlZ Branch Committee GirlZ Branch OperatorZeimeet
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