In the anime, Usagi calls him Motoki-oniisan and has a very big crush on him in the beginning of the series. He is also friends with Mamoru Chiba, who attends the same college he does, Azabu Institute of Technology. His girlfriend is Reika, a wonderful science student. He has a little sister, Unazuki, who is also friends with Usagi and the others.

In the manga, Motoki holds part-time jobs at both the Crown Game Center and the Crown Fruit Parlor. He attends KO University. In the first arc of the manga, he recognizes the Senshi and learns their true identities, but promises not to tell anyone.