When I watch the anime I get excited by Koro-Sensei's new student, Itona. He has many similarities with koro-sensei. So, my question is: why do they look different? Koro-sensei is like an octopus and Itona is like a human.

  • Your question doesn't mention a Tako? did you mean Itona in the title? May 7, 2015 at 12:10
  • Yeah hehe. I mean why Itona didn't look like tako(octopus) like koro-sensei. @ToshinouKyouko
    – enjeru
    May 7, 2015 at 12:24
  • Ah I see now :) May 7, 2015 at 12:25
  • hehe. Sorry I make you confused :p @ToshinouKyouko
    – enjeru
    May 7, 2015 at 12:26

4 Answers 4


Itona isn't a relation of Koro-sensei.

He is the son of Horibe Electronics Factory's former president. After his father's company went bankrupt, Itona was abandoned by him which became a source of bullying towards him as well. One night, he was found by Shiro who told him that in his eye lies a tenacity for power and that he would help him achieve that power in order to grasp victory.

See more: http://ansatsukyoshitsu.wikia.com/wiki/Itona_Horibe

I presume the similarities lie in the tentacles. Itona's powers are manufactured by scientists, wheras Koro-sensei is an octopus alien.

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  • Ah I get it. Sorry I don't read the manga so I didn't know hehe.
    – enjeru
    May 7, 2015 at 12:23
  • No problem :) it's a good read May 7, 2015 at 12:26
  • @ToshinouKyouko well if you actually read the latest grey area translations, it's revealed that Koro-Sensei actually isn't an alien......
    – Vogel612
    May 7, 2015 at 12:29
  • @Vogel612 :o I haven't read it since the anime started. Feel free to post a better answer :) May 7, 2015 at 12:38
  • @ToshinouKyouko your answer as far as Itona and Koro-sensei's relationship is 100% correct as far as we know from the manga, so I don't think the answer needs improving per se.
    – Daboyzuk
    May 7, 2015 at 13:01

As @Toshinou Kyouko explained, Itona and Korosensei aren't actually related.

Koro-sensei was...

... originally the subject of human experimentation. His powers are the result of the experiments that were run on his own body.

Itona is considered being Koro-sensei's brother because...

... he received his tentacles from the same scientists who experimented on Koro-sensei. His powers are inherited from Koro-sensei.

As for why they don't look alike:

Itona had his tentacles implanted into him. Those tentacles were most likely originally part of Koro-sensei's body after the latter turned into the octopus we now know and "love". Unlike Koro-sensei, his body didn't actually change.


Koro-sensei and Itona are not blood related at all, it's the tentacles that make them both fall in the same category "family".

This brother relationship was first mentioned by the official guardian, as to make Itona confused about his relationship with Koro-sensei. He intended to kill Koro-sensei with the help of an enraged Itona, but as obviously failed.


Koro sensei was actually human once , he was formerly the reaper before his apprentice turned him in and stole his name, he was then experimented on by shiro and grew the tentacles after escaping the facility and killing his best friend and destroying the facility.

  • Please include relevant sources/references. If possible, avoid repeating information from previous answers.
    – W. Are
    May 28, 2019 at 19:59

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