Listen. When it comes to fighting... it's all about making use of your particular strengths.
Ken Ishiyama to Eijiro Kirishima and Rikido Sato in "Stripping the Varnish"

This article is about the U.A. High teacher. For the Pro Hero known as Rock Lock, see Ken Takagi.

Ken Ishiyama ( (いし) (やま) (けん) Ishiyama Ken?), also known by his hero name Cementoss (セメントス Sementosu?), is a Pro Hero and member of the U.A. High School faculty where he teaches Modern Literature.


Cementoss appears to be a humanoid block of cement with black eyes and gray hair tied into a short ponytail. His body shape is evenly blocky all around his body. His eyes are generally closed and his lips are pulled upwards. His hero costume consists of a sleeveless brown suit that includes yellow stripes, shorts, and an elongated collar. He also sports gray shoes with yellow soles.


Cementoss is an often serious yet pleasant individual. He is very careful of the well being of others. He did not allow Eijiro to compromise All Might's identity [1] and also wanted to stop the match between Izuku and Shoto, noting that Izuku's injuries were serious enough to stop the bout.[2]


Entrance Exam Arc

Cementoss first appears as a part of U.A. High's judging panel during the Entrance Exams. He is visually surprised when Izuku Midoriya uses his Quirk to destroy the giant robotic villain in a single punch.[3]

U.S.J. Arc

Cementoss arrives with his fellow faculty members when Tenya Iida brings them to the U.S.J to halt the League of Villains' assault. He uses his Quirk to create a wall between All Might, Izuku, and Eijiro to protect All Might's identity. He tells Eijiro it's dangerous and commands him to return with his class. All Might thanks Cementoss for this, and Cementoss replies that he's actually a big fan of the number one hero.[1]

U.A. Sports Festival Arc

Cementoss sports festival

Cementoss acts as the proctor for the fighting tournaments.

During the U.A. Sports Festival's final event, Cementoss acts as the proctor for the one on one fighting tournament. He creates the ring where the combatants will fight and a chair for himself to sit. He sits down and warns the participants that he will step in if things get too rough.[4]

During the fight between Izuku and Shoto, Cementoss contacts Midnight and asks her if they should stop their fight because of Izuku's reckless fighting. He adds that his adrenaline is blinding him from how serious his injuries are and that Recovery Girl likely won't be able to heal him in a single session. He also says Izuku may not even be able to fight in his next match even if he wins. They allow the two to continue fighting until the climax of their bout. Worried that the two may kill one another, Cementoss and Midnight step in. However, Izuku's and Shoto's attacks hit Cementoss's cement pillars and creates a shockwave that destroys the entire arena. After the smoke from the collision clears, Cementoss comments that although great power isn't always a good thing, he finds Shoto and Izuku both amazing.[2]

Vs. Hero Killer Arc

Following the U.A. Sports Festival, U.A. students receive internship opportunities from Pros hoping to draft them. In the faculty room, Cementoss informs All Might that a new nomination has arrived for Izuku.[5]

Final Exams Arc

Prior to Final Exams at the end of the first years' first term, Cementoss meets with his fellow faculty members. They discuss changing the finals format from facing robotic villains to fighting against the teachers. Cementoss comments that this may be too difficult for the students, but they all ultimately agree on the change. Cementoss joins the other teachers at the Final Exams practical portion test site to meet Class 1-A.[6]Cementoss is placed against Eijiro and Rikido Sato in the first match.

Cementoss defeats Eijiro and Rikido

Cementoss defeats Rikido and Eijiro in the first term final.

The three of them arrive in a replica city area where their battle begins. Cementoss begins by using his Quirk to create many cement walls to block their advance from the front. Eijiro and Rikido use their Quirks to smash their way through the walls, but Cementoss continues to create more. As both the student's Quirks work on a limit, Cementoss holds the advantage in a drawn-out battle. Cementoss informs the duo of their weakness as he overwhelms them with cement and knocks them out.[7]

Provisional Hero License Exam Arc

Cementoss, Midnight, and Ectoplasm join Shota Aizawa in his homeroom class to announce that Class 1-A needs to develop super moves.[8] They move to Gym Gamma where the teachers announce that the students will need special moves for the upcoming Provisional Hero License Exam. Cementoss uses his Quirk to create stages for each student to fight one of Ectoplasm's clones.[9]

Paranormal Liberation War Arc

Cementoss assists his allies in the Paranormal Liberation Raid by using his Quirk to tear open the Paranormal Liberation Front's Gunga Mountain Villa hideout.[10]


Modern Literature Expertise: Ken teaches high school modern literature. This suggests that he is well versed in the subject.


Cement (セメント Semento): Ken's Quirk allows him to manipulate any cement based material that he touches, allowing him to shape it into various forms. His Quirk doesn't appear to have a time limit, and Recovery Girl mentioned his Quirk is among the most difficult of the U.A. teachers to fight against.[11]


3/5 C
2/5 D
5/5 A
5/5 A
4/5 B
Ken's stats, according to the Ultra Archive Book

4/6 B+
5/6 A
5/6 A
5/6 A
1/6 E
Ken's stats, according to the Ultra Analysis Book

Battles & Events

Battles & Events

Character Appearances

U.S.J. Arc
12. Yeah, Just Do Your Best, Iida! Absent
13. Rescue Training Absent
14. Encounter with the Unknown Absent
15. Vs. Absent
16. Know Your Enemies Absent
17. Game Over Absent
18. Heroes' Counterattack Absent
19. All Might Absent
20. The World of Pros Debut
21. In Each of Our Hearts Appears
U.A. Sports Festival Arc
22. That's the Idea, Ochaco Appears
23. Roaring Sports Festival Absent
24. Mad Dash and Knockdown Absent
25. In Their Own Quirky Ways Absent
26. Chase Down the Leader Absent
27. Earth-Shatteringly Fateful Negotiations Absent
28. Strats, Strats, Strats Absent
29. Unaware Absent
30. Cavalry-Match Finale Absent
31. The Boy Born with Everything Absent
32. Smile, Prince of Nonsense Land! Appears
33. Shinso's Situation Absent
34. Victory or Defeat Absent
35. Battle On, Challengers! Absent
36. Bakugo vs Uraraka Appears
37. Midoriya and Endeavor Appears
38. Todoroki vs. Midoriya Absent
39. Shoto Todoroki: Origin Appears
40. Emancipation Appears
41. Fight On, Iida! Absent
42. Final-Match Time Absent
43. Todoroki vs. Bakugo Absent
44. Relaxing Day Off Absent
Vs. Hero Killer Arc
45. Time to Pick Some Names Appears
46. Bizzarre! Gran Torino Appears Absent
47. Struggling Absent
48. Getting the Knack Absent
49. Midoriya and Shigaraki Absent
50. Kill'Em Dead Absent
51. No, Knock it Off, Iida! Absent
52. Hero Killer Stain vs. U.A. Students Absent
53. From Todoroki to Iida Absent
54. Re: Ingenium Absent
55. Conclusion?! Absent
56. Conclusion Absent
57. The Aftermath of Hero Killer Stain Absent
58. Internship's End Absent
59. Listen Up! A Tale From the Past Absent
Final Exams Arc
60. Gear Up For Final Exams Appears
61. The Worst Combo Appears
62. Katsuki Bakugo: Origin Absent
63. Yaoyorozu Rising Absent
64. The Task at Hand Absent
65. Wall Absent
66. Midoriya's Observations Absent
67. Stripping the Varnish Appears
68. Encounter Absent
69. Interview with Midoriya Absent
Provisional Hero License Exam Arc
98. Moving into Dorms Absent
99. Goodbye Two-Digit Chapters, Hello Three Digits Appears
100. Creating Ultimate Moves Appears
101. The Girl Called Mei Hatsume Absent
102. On Cloud Nine Appears
103. The Test Absent
104. White-Hot Battle! To Each Their Own Strengths! Absent
105. Shiketsu High Lurking Absent
106. Class 1-A Absent
107. Denki Kaminari's Thoughts Absent
108. RUSH! Absent
109. Rescue Exercise Absent
110. Rescue Exercise Continued Absent
111. Smoldering Start Absent
112. What's the Big Idea? Absent
113. Test's Aftermath Absent
114. Result's Aftermath Absent
115. Unleashed Absent
116. Meeting in Tartarus Absent
117. A Talk About Your Quirk Absent
118. Meaningless Battle Absent
119. Deku vs. Kacchan, Part 2 Absent
120. The Three Absent
121. Second Semester Opening Ceremony Absent
Shie Hassaikai Arc
122. A Season for Encounters Absent
123. Unrivaled Absent
124. Trouble Ahead!! Episode: Work Studies Absent
125. Overhaul Absent
126. Open Up, World Appears
127. Sir Nighteye and Izuku Midoriya and Mirio Togata and All Might Absent
128. Boy Meets... Absent
129. Eri Absent
130. Listen to the Truth Appears
131. Fighting Fate Absent
132. The Plan Absent
133. Catch Up, Kirishima Absent
134. Let's Go, Gutsy Red Riot Absent
135. An Unpleasant Talk Absent
136. Close at Hand!! Absent
137. Restraint!! Absent
138. Go!! Absent
139. Shudder! The Underground Labyrinth Absent
140. Suneater of the Big Three Absent
141. Hassaikai: Behind the Scenes Absent
142. Shield and Shield, Spear and Shield Absent
143. Let’s Rumble, Rappa!! Absent
144. Red Riot, Part 1 Absent
145. Red Riot, Part 2 Absent
146. Temp Squad Absent
147. Twoga!! Absent
148. The Anguish of Young Twoga Absent
149. Don't Get Mad, Irinaka Absent
150. Mirio Togata Absent
151. Mirio Togata!! Absent
152. Lemillion Absent
153. Transform! Absent
154. Unforeseen Hope Absent
155. Saviors, the Saved and a Hero's Place Absent
156. The Power of Those Saved Absent
157. Infinite 100 Percent Absent
158. Chisaki's Warped Compassion Absent
159. It's Over!! Absent
160. Expressway Absent
161. Bright Future Absent
162. Suitable One Absent
Remedial Course Arc
163. Smoldering Flames Absent
164. Masegaki Absent
165. Win Those Kids' Hearts Absent
166. Be Proud, License Trainees Absent
167. Number One Hero's Starting Line Absent
168. The Strange Tale of Aoyama Appears
Endeavor Agency Arc
241. Do That Interview! Absent
242. Have a Merry Christmas! Appears
243. Off to Endeavor's Agency! Appears
244. Recommended Reading Absent
245. Rise to Action Absent
246. Message Absent
247. Status Report! Absent
248. One Thing at a Time Absent
249. The Hellish Todoroki Family Absent
250. Ending Absent
251. Just One Week Absent
252. The Unforgiven Absent
Paranormal Liberation War Arc
253. Shirakumo Absent
254. You Could Be More of a Hero than Anyone Absent
255. Hero Hopeful Absent
256. The High, Deep Blue Sky Absent
257. Pass It Forward, to Whomever Absent
258. Friends Absent
259. A Quiet Beginning Appears
260. Life's Work Absent
261. High-Ends Absent
262. Mirko, the No. 5 Hero Absent
263. I Wanna Be With You Guys!! Appears
264. One's Justice Appears
265. Villains and Heroes Absent
266. Happy Life Absent
267. Flames Absent
268. Scramble! Absent
269. The Three of Us Absent
270. Inheritance Absent
271. Dark Cloud Absent
272. Good Morning! Absent
273. The Thrill of Destruction Absent
274. Search Absent
275. Encounter, Part 2 Absent
276. You Cheated...! Absent


  • "Ken" (?) means "stiff, firm, hard". "Ishiyama" (石山?) means "Stone Mountain". "Cementoss" is possibly a combination of "cement" and "toss".
  • According to Volume 4:
    • He's a big fan of All Might.
    • He likes round things (whilst being, ironically, blocky).
    • His favorite food is manju.
    • On his profile in Volume 4, the author commented that he should have given Ken's hair a crew cut.
  • Cementoss shares his first name with Ken Takagi, the "Pro Hero: Rock Lock".
  • He shares the same voice actor with Masaki Mizushima, otherwise known as "Normal Hero: Manual".



  1. 1.0 1.1 My Hero Academia Anime: Episode 13.
  2. 2.0 2.1 My Hero Academia Anime: Episode 23.
  3. My Hero Academia Anime: Episode 4.
  4. My Hero Academia Anime: Episode 19.
  5. My Hero Academia Manga and Anime: Chapter 45 and Episode 26.
  6. My Hero Academia Manga: Chapter 60.
  7. My Hero Academia Manga and Anime: Chapter 67 and Episode 34.
  8. My Hero Academia Manga and Anime: Chapter 99 and Episode 52.
  9. My Hero Academia Manga and Anime: Chapter 100 and Episode 52.
  10. My Hero Academia Manga: Chapter 263.
  11. My Hero Academia Anime: Episode 35.
  12. My Hero Academia Manga: Chapter 67 (p. 2).

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