|This article is about a/an actor in the TV special Birth of the 10th! Kamen Riders All Together!!.|
Dr. Hajime Kaido (海堂 肇博士 Kaidō Hajime Hakase) - He is Ryo's father's friend and is the researcher of the biochemistry which is also the teacher of a university. He cooperates in Ryō unstintingly.
Behind the scenes
Dr. Hajime Kaidō was played by Eiji Karasawa (柄沢 英二 Karasawa Eiji).
- Birth of the 10th! Kamen Riders All Together!!
- Kamen Rider 1 Through RX: Big Gathering (archive footage only)