This article is about the U.A. High teacher. For the Pro Hero known as Rock Lock, see Ken Takagi.
Ken Ishiyama (石山堅,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, seemingly shut eyes and gray hair tied into a short ponytail. His body shape is evenly blocky all around his body. His eyes are generally closed (but tiny when opened) 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 in the manga.
Cementoss is an often serious yet pleasant individual. He is very careful of the well being of others. He did not allow Eijiro Kirishima to compromise All Might's identity  and also wanted to stop the match between Izuku Midoriya and Shoto Todoroki, noting that Izuku's injuries were serious enough to stop the bout.
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 deform the object into various shapes and sizes, changing it’s appearance. 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.
Cementoss considers himself a big fan of All Might despite the fact that he is also a Pro Hero. Like the rest of the professors at the U.A. He knows his secret identity and he does his best to prevent others from discovering it. He also knows about All Might's stomach wound and how this limits his ability to use his Quirk, so Cementoss cares about his health and advises him not to overdo it when he performs his duties as a hero.
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