Koji is a Stand User who wields Blue Thunder, a Stand that can generate helicopter rotors on his or anyone else's body. He is the counterpart of Koichi Hirose in the 37th universe and is friends with Rohan Kishibe, Muryotaisu Nijimura, Fukashigi Nijimura, and Reimi Sugimoto. He later befriends Jorge Joestar and assists him with finding Yoshikage Kira.
Koji is a short, skinny teenage boy with spiky hair. He has a few thin bangs on his forehead. Koji resembles Koichi Hirose from the first universe and also wears a Japanese school uniform. When he fought Yoshikage Kira in the past, Koji's uniform was a black gakuran. During the summer when the story takes place, his uniform consists of a collared t-shirt with the top unbuttoned and trousers.
Koji is an amiable teenager who can also be reliable. Unlike his friends, he is not as rowdy. Jorge says that Koji appears like a nice kid and doesn't seem like the type to be friends with the two he hangs out with. He is friendly with strangers but also perceptive, as he watches Jorge carefully when they first meet just in case Jorge is an enemy Stand user.
Koji is humble about his Stand, thinking it looks lame despite its usefulness in both transportation and combat.
- Main article: Blue Thunder
Koji's Stand allows him to spawn propellers on either his or anyone else's bodies. He typically places them on his head enabling him to fly, but he can also place them on his hands to generate gusts of wind. The size of the propellers can be adjusted as well.
- JORGE JOESTAR Chapter 4: Morioh
- Based on his age.