Koji is tall, and has a large muscular build. His head has the form of a rock, which is unevenly shaped and pointed at the top of his head, and his jaw is square shaped. His skin is peach colored.
Koji is a very shy and quiet person. As such, he rarely speaks and prefers using sign language to communicate with his classmates. According to Fumikage Tokoyami, he is very good at keeping secrets.
He appears to enjoy the company of animals, even owning a small rabbit as a pet. With his Quirk, Koji can interact with them in ways others can't. He also owns a few animal plushies and decorations in his room, implying that he likes cute things.
Koji suffers from Entomophobia, being deathly afraid of bugs, with the mere sight of them making him scream and run away in fear. However, Koji is capable of (reluctantly) putting this fear aside if it means helping his comrades.
Quirk and Abilities
- Koji's known U.A. data is as follows:
- His name contains the kanji for mouth (口?), field (田?), shell (甲?), and boss (司?).
- He likes nature.
- He is from the Tohoku region of Japan.
- Kohei Horikoshi likes his design as it deviates away from human form.
- Koji's first line of dialogue happened in Chapter 66, 61 chapters after his debut.
- With his birthday taking place in February, Koji is the third youngest student in Class 1-A, as everyone was 15 when they started U.A.'s school year in early April.
- (To himself) "That's right. I got into U.A. High, my dream school... At U.A., it's always about moving forward! That's what we tell ourselves... Plus Ultra!!"