He is a student in Class 1-A at U.A. High School who is training to become a Pro Hero.
Koji is a tall young boy of a wide, muscular build with peach-colored skin. His head takes the form of a rock, which is unevenly shaped and pointed at the top of his head, and his jaw is square-shaped.
He has a hero costume with a tight yellow suit, only reaching to his knees and elbows, with a large red marking over his torso and at the ends of his sleeves. On his chest, there is a symbol resembling an open mouth, and he wears yellow shoes with red lining.
As of the Provisional Hero License Exam, he added two white straps over his shoulders and wears a mask that covers his entire face, with holes above over his mouth so his voice still can be heard when he's using his Quirk. His shoes were changed out in favor of boots.
Despite his brutish appearance, Koji is a very shy and quiet person. He rarely speaks and usually prefers using sign language to communicate with his classmates, so much so that Kyoka Jiro assumed that he was mute and was greatly surprised when Koji spoke.
According to Fumikage Tokoyami, he is very good at keeping secrets. Koji also really hates violence due to his friendly and kind-hearted nature.
- His favorite thing is nature.
- He is the only student in Class 1-A to have a pet which is a white rabbit.