Genpachiro Otta is a lieutenant in the Metropolitan Police's First Investigation Division, the first group to be sent out to investigate crimes. He serves as a liaison between his division and the Special Investigations Division. He often dismisses the actions of the Special Investigations Division as that of an "occult club", but he is in fact quite fond of Shinnosuke, a fact he tries to hide. After the Special Investigations Division is disbanded, Otta is promoted to police inspector. He later becomes the chief of the First Investigation Division.
In the events of the film Super Hero Taisen GP: Kamen Rider 3, Otta has been turned into a general in Shocker and has become the monster Cheetahkatatsumuri. He is destroyed by the combined efforts of Kamen Riders 1, 2, and 3, but is brought back to life as a normal human when the timeline is restored to normal.