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Whatever I might say to you, I know you'll do what you have to and save the people who need saving. You'll give it all you've got and then some. It's that iron will that can turn things around and make the impossible, possible. I know that you can do it, and I know that you will. Don't doubt yourself. Just act. Fly, Koichi. Fly, Hero.
Iwao Oguro's letter to Koichi Haimawari in "Letter"

Iwao Oguro ( () (ぐろ) (いわお) Oguro Iwao?)[3], commonly known as Master (師匠 Shishō?), is the vigilante known as Knuckleduster (ナックルダスター Nakkurudasutā?). He was formerly the Pro Hero High-Speed Hero: O'Clock (超速ヒーロー・オクロック Chōsoku Hīrō Okurokku?) in Japan, and Hyper Quadfist ( (チャオ) (ピン) (スー) (チェン) Chaopin sūchen?) in China.[4]


Knuckleduster is a towering, heavily muscled man. He has short dark hair and visibly thick eyebrows, and also possesses heavy stubble and a prominent scar running diagonally down his left cheek.

His costume consists of a simple wrap-around black mask tied over the top of his head, a tight-fitting dark shirt, jeans, boots, and a long hunter green trench coat. On his hands, he wears a pair of dark gloves topped with a pair of brass knuckles, or knuckledusters, from which he derives his name.

After his initial encounter with Number 6, his right leg is busted to the point of requiring a cane to walk, and also appears to have his left eye completely scarred over.

As O'Clock he wore a full-body red suit and a mask that covered his eyes and half of his face. He also wore gloves and boots, and his suit had several lines around the arms, legs, and torso. On his shoulders, he had what appeared to be his symbol. He was noticeably slimmer at the time, though still quite muscular.



Knuckleduster is an individual with a strong sense of justice and drives to do the right thing. He has no government-issued hero license, but this does not stop him from putting on his costume and going out every night to fight street-level criminals and local gangs to keep his neighborhood safe from crimes most "heroes" will not bother with. Despite this reckless streak, he does genuinely admire Heroes for the work they do. This is probably because he also used to be a Pro Hero before his powers were stolen, which left him Quirkless.

Knuckleduster is known for his violent nature.

Knuckleduster shows no resentment towards people who do and shows no fear towards villains who have powerful Quirks. In fact, he seems to love fighting against particularly strong people who have powerful Quirks, enjoying the challenge and becoming very upset or frustrated whenever there are no particularly strong Villains to fight. When a fight is too easy, he quickly becomes depressed. This seems to be one of the main joys of his life, as he becomes invigorated whenever he gets to fight a strong opponent. He is even willing to fight against Pro Heroes if the situation calls for it.

Knuckleduster seems to be a person with a tendency to use violence to solve any problem. He prefers to punch first and ask questions later, as he is willing to beat up people he deems to look suspicious on the slim chance that they may be villains or users of the Trigger drug, forcing his teammates to hold him back before he goes too far. His attitude extends to that he was willing to attack a young-appearing woman under the suspicion of being a villain. Knuckleduster feels little to no guilt or worries about what he does, despite the fact that he could have been registered as a Villain if the misunderstanding continued, showing a more aloof and careless side to his personality.

However, despite this, he has proven to be more intelligent and perceptive than he seems to be at first. His conclusions are usually right, proving to have a great capacity for deduction. During fights he is able to devise strategies and stratagems very quickly to deal with villains with dangerous or problematic Quirks, knowing when is the best time to attack or what item is the most adequate to defeat them. And when he is not wearing his vigilante attire, he can behave like a well-mannered and polite person, presenting a perfect façade of a worker for a local non-profit organization, complete with business cards and a technically true spiel about the group.

Iwao taking care of his wife.

The truth is, underneath his intimidating exterior and violent behavior, Knuckleduster is actually a very caring and compassionate individual who cares for the people close to him and encourages them to achieve their goals. He trains Koichi Haimawari to improve his combat style and his Quirk and is proud of his progress. He is also a loving father and husband who holds a deep grudge against the people who hurt his family.

During his time as O'Clock, he was a stoic Hero known for quick "snatch and grab" approaches to solving crimes, thanks to his Overclock speed, along with his frequent partnerships with the Police Force, specifically Eizo Tanuma. However upon reflection after losing his Quirk, he feels that "O'Clock" was a failure as a hero, representing as merely another cog in the system that only fixed problems on the surface. This also being one of the many reasons for his denying of Number 6's request to become O'Clock's successor, believing O'Clock not to be a hero that should be idolized.

Despite his attempts to initially deny it during the Underground Masquerade, Kendo Rappa was able to recognize that, just like him, Iwao loved the thrill of a no holds barred fight and getting his hands dirty, which clashed with his supposed image as O'Clock. When he embraced his Knuckleduster persona, Kendo's belief turned out to be right as Knuckleduster allowed that more chaotic side of his personality to be unleashed.


Overall Abilities: Knuckleduster is currently Quirkless, proven when Eraser Head tried to erase his Quirk to no avail. Despite this, however, Knuckleduster still possesses a large amount of physical strength and skill, which enabled him to fight on even terms even with a Pro Hero like Eraser Head. Knuckleduster appears to be skilled in hand-to-hand combat, utilizing brass knuckles as his weapon of choice. Knuckleduster's skill with his fists was great enough to overcome the swordsmanship of Stendhal, a powerful and notorious Vigilante, landing a heavy blow before the vigilante could scratch him, single-handedly defeating the swordsman. During his time as a Pro Hero, he went undercover and fought Kendo Rappa in a cage match, managing to stay conscious and unharmed after the villain used his Strongarm, an impressive feat considering the power of his Quirk and how easily he defeated most of his opponents with it.

  • Enhanced Durability: Despite being Quirkless, Knuckleduster is very sturdy, standing up even when he receives blows from physical enhancement Quirks. Perhaps more impressive is how he is able to withstand Kendo's Strongarm blows, which individually were powerful enough to break Eijiro Kirishima's Red Riot Unbreakable.
  • Enhanced Strength: Knuckleduster's strength is surprisingly high, and he is sometimes mistaken for having a strength-enhancing Quirk. He was capable of going fist to fist with a tremendously physically powerful and fast-moving Trigger-enhanced man and knock him out with relative ease.[5]

Keen Intellect: Despite appearing to be a mere brawler, Knuckleduster has great intuition and tactical knowledge. When fighting Trigger-enhanced villains, he is able to work out how their Quirks work and the best way to counter them all while locked in a fight with them.[6] He also quickly understood Stendhal's way of fighting as well as his state of mind,[7] and also preemptively formulated a battle plan that would allow him to defeat Kuin Hachisuka whilst also saving the life of his daughter, Tamao.[8]

Former Quirk

Iwao using his heightened speed and perception.

Overclock (オーバークロック Ōbākurokku?): Iwao's Quirk allowed him to accelerate his brain's perception to extreme speeds, making it appear to him as if the world was moving in slow motion. While his Quirk was active, his accelerated perception granted him increased physical speed.

The Quirk requires a cool-down period after it's used, and can only be used for a few seconds at a time.[9]

At some point in the past, Iwao's Quirk was stolen by All For One, leaving him Quirkless.[10][11]

  • Heightened Focus: Thanks to his Quirk, O'Clock could see, hear, and think at hyper speed.[12]


Brass Knuckles: Knuckleduster's main weapons and the reason for his Vigilante name.

Grappling Hook: Knuckleduster has been seen swinging from buildings by means of a grappling hook.

Painkillers: Used to tone down pain. Bought regularly from Giran.[13]

Taser Knuckle: A taser weapon with a built-in defibrillator. Bought off Giran.[14]

Pheromone Cocktail: An explosive cocktail made to draw in bees and then explode. Made with items obtained from Giran.[15]

Sniper Rifle: A high-precision firearm, which allows shooting at a very long distance.[16]

Radio Box: A regular radio box used against Number 6 to counter his usage of Overclock.

Shotgun: A firearm used for close range encounters.[17]

Battles & Events

Battles & Events

Chapter Appearances

Vigilantes Beginnings Arc
1. "I'm Here" Appears
2. Takeoff Appears
3. Nice Guy Reborn Appears
4. Honesty Appears
5. Bee Appears
6. No Need to Hold Back Appears
6+ Alpha. Hero Conference Flashback
6+ Beta. Hero Visit Absent
7. Top Runner Appears
7.5. Appearance Matters Appears
8. Him Appears
Stendhal Arc
9. Judgment Appears
9.5. Mask Absent
10. Scream Appears
11. Crossing Lines Appears
Vs. Queen Bee Arc
12. Senpai Flashback
13. Makoto/Truth Appears
14. MAJOR Appears
15. Playboy Appears
16. Mom Descends Appears
17. Tag Team! Appears
18. Force of Will Acceleration! Appears
19. Family Appears
20. Event Announcement! Appears
21. Ensemble, Assemble! Absent
22. The Day Of Appears
23. Daughter Appears
24. A Father-Daughter Talk Appears
25. Goodbye to Dad Appears
26. Tamao Appears
27. Business as Usual Appears
28. What a Man Takes with Him Appears
Osaka Incident Arc
29. Equipment Issues Fantasy
30. Cooperation Request Flashback
31. Day-Tripping Down to Naniwa! Absent
32. Idols Keep Their Secrets! Absent
33. Stumbling into Nasty Business! Absent
34. Crabtastic Rampage! Absent
35. Blown-Up Hero?! See Ya Later! Absent
Sky Egg Arc
36. Must-Have Merchandise Absent
37. Public and Private Absent
38. High-Speed Flashback
39. A Rational Man Flashback
40. A Rational Team-Up Absent
41. Ultimate Move! Fantasy
42. Mixer Absent
43. Casanova Absent
44. One Outrageous Traveler Appears
45. The Man Returns Appears
46. Christmas Eve Hero Absent
47. Farewell Party! Flashback
48. Investigation Start! Steamy Romance Spotted?! Absent
49. Zero Hour Absent
50. Defend the Tower! Absent
51. I Do What I Can Absent
52. Balloon Soul Absent
53. Limits and Catastrophe Absent
54. Hotline Absent
55. This Is a Hero!! Appears
56. I'm No Hero Appears
57. Explosive Man Appears
58. International Flight Home Fantasy
School Days Arc
59. Rain and Cloud Absent
60. Taking in a Stray Absent
61. Two as One Absent
62. Glass Sky Absent
63. Find That Resolve Absent
64. Fight On, Shota Absent
65. A Sky with No Rain Left Flashback
Final Performance Arc
66. Graduation and Career Path Absent
67. Professional / International / Spicy Curry Absent
68. I'd Better Not Lose Absent
69. Hero on the Scene Absent
70. True Self Absent
71. Thanks for the Guidance Flashback
72. Searching for You Absent
73. The Queen Descends Absent
74. After the Storm Flashback
75. Letter Flashback
76. Deadly Weapon Pictured
77. Strategy Absent
78. Dispatch Absent
79. Inferno Number Two Absent
80. Who's That, Now? Absent
81. Bee My Pop Mentioned
82. High-Speed Hero II Absent
83. Earthbound Perp Absent
84. Dreams of a Hero Absent
85. Questioning Pictured
Underground Masquerade Arc
86. Underground Fighting Tournament Flashback
87. Rap Rap Rap Appears
88. Hidden Face, Bare Ears Appears
89. Super-Smashing Tiger Bunny! Appears
90. Team-Up in the Underground Appears
91. Dash Ahead to Plan B Appears
92. Might Signal Appears
93. Three-Second-Back-and-Forth Appears
94. Underground Roots Flashback
94.5. Tanuma Report Pictured
Naruhata Lockdown Arc
95. Moon Mentioned
96. Negotiations Flashback
97. Pursuers Absent
98. Intentional Persuasion Technique Disguise
99. Invasion of the Faceless Disguise
100. Super Explosion! Disguise
101. Fly at Night Absent
102. Intruder Disguise
103. Aim for the Head Disguise
104. This Face Flashback
105. Escape Start Disguise
106. Chase of Crawlers Disguise
107. A Hundred Hits Disguise
108. Things That Live in the Abyss Disguise
109. Encirclement Disguise
110. Careless Appears
111. Return of the Fist Appears
112. The Ends to Miscalculation Appears
113. The Worst Villain Fantasy
114. Dogfight Appears
115. Conclusion to Power Absent
116. The Final Lesson Appears
117. The Absolute Worst One Fantasy
118. Golden Age Fantasy
119. That's Why I'm... Absent
120. Rootin' For Ya! Fantasy
121. Reinforcements Arrive Absent
122. One-Two Finish Absent
123. Bye Bye, Hero Appears
124. Forever Absent
125. Each of Our Futures Absent
126. The Skycrawler Rising Appears


  • Iwao's surname contains the kanji for "male" ( o?) and "black" ( guro?), and his first name contains "rock, crag" ( iwao?).
  • Knuckleduster's favorite things are cigarettes and beer.
  • His vigilante name is another name for the brass knuckles that form a part of his costume.
  • Hideyuki Furuhashi, the author of Vigilantes, said that if All Might was Superman, Iwao would be comparable to Batman.
  • Furuhashi confirmed that O'Clock's Costume is based on DC Comics' The Flash.[18]


  1. My Hero Academia: Vigilantes Manga: Chapter 16.
  2. My Hero Academia: Vigilantes Manga: Chapter 19.
  3. My Hero Academia: Vigilantes Manga: Chapter 19.
  4. My Hero Academia: Vigilantes Manga: Chapter 44.
  5. My Hero Academia: Vigilantes Manga: Chapter 6.
  6. My Hero Academia: Vigilantes Manga: Chapter 6.
  7. My Hero Academia: Vigilantes Manga: Chapter 11.
  8. My Hero Academia: Vigilantes Manga: Chapter 26.
  9. My Hero Academia: Vigilantes Manga: Chapter 38.
  10. My Hero Academia: Vigilantes Manga: Chapter 44.
  11. My Hero Academia: Vigilantes Manga: Chapter 75.
  12. My Hero Academia: Vigilantes Manga: Chapter 38.
  13. My Hero Academia: Vigilantes Manga: Chapter 26.
  14. My Hero Academia: Vigilantes Manga: Chapter 26.
  15. My Hero Academia: Vigilantes Manga: Chapter 26.
  16. My Hero Academia: Vigilantes Manga: Chapter 55.
  17. My Hero Academia: Vigilantes Manga: Chapter 57.
  18. My Hero Academia: Vigilantes Manga: Vol.6, Omake

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