Doctor Mochizuki
An ambitious geneticist who turned Masaru into ZO and then created the Neo Organism. His dream was to create the 'perfect life-form', but instead it turned on him and was held captive by his creation. He used grasshoppers as a means to contact ZO via telepathy.
Hiroshi Mochizuki
A young boy who lives with his grandfather Seikichi and targeted by the Neo Organism. Hiroshi longed to be with his father, who had gone missing years ago. As a memento, Doctor Mochizuki gave Hiroshi a pocket watch that played music. Hiroshi was at first afraid of ZO, but as ZO proved he truly was a friend, Hiroshi affectionately referred to ZO as 'Oni-chan' (brother).
Seikichi Mochizuki
The grandfather of Hiroshi and father to the Doctor who started the whole mess.
She has a karate class and had a misunderstanding with Masaru. ZO battles Koumori Man to cover Hiroshi and Reiko's escape before they are sucked in a pocket dimension by Kumo Woman.
Series:  Kamen Rider ZO