The Inhumanoids in
Kamen Rider: The First are not non-humans as their name would suggest, but rather
cyborgs much like the Kamen Riders. The organization's ranks are depicted as having three commanding characters (seen only on screens), as well as several special-class soldiers and unidentified grunts. •
Masaya Kikawada as , a college student and motorcycle enthusiasts who was abducted by Shocker and converted into the Inhumanoid , a special-class soldier charged with the carrying out of covert search-and-destroy missions. He later regained his sense of self and defects from Shocker, instead fighting against them as the Kamen Rider, who later re-dubbed himself as Kamen Rider 1. •
Hassei Takano as , a man who competes for Asuka's affection who can transform into , a special-class soldier in the Shocker ranks charged with hunting and eliminating the traitor, Hopper 1. He later begins fighting against Shocker, alongside Hongo, as Kamen Rider 2. • Takano also portrayed Katsuhiko Yano, Asuka's late fiancé, in a dual role. •
Rena Komine as , a journalist who initially accused Hongo for the murder of her fiancee and fellow reporter before she fell in love with him upon learning the truth. •
Hiroshi Miyauchi as , the owner of a motorcycle shop where Hongo receives the Cyclone motorcycle. •
Eiji Wentz as , an ill teenager who was inducted into Shocker as the Inhumanoid , a special class soldier assigned to Bat's squadron, and later works independently alongside his romantic interest, Snake. •
Ryoko Kobayashi as , Haruhiko's romantic interest and a fellow ill teenager who was inducted into Shocker as the Inhumanoid , a special class soldier assigned to Bat's squadron, and later works independently alongside Cobra. •
Mayumi Sada as , a female commander in the Shocker ranks, she is responsible for the selecting of new Inhumanoid candidates to be inducted into the organization. Like Dr. Shinigami, "Lady" only appears via satellite on screens in the Shocker headquarters, and her physical whereabouts are unknown. •
Issa Hentona as , a young male commander in the Shocker ranks, he is responsible for the organization of missions and troop deployment. Like Dr. Shinagami and "Lady", "Youth" only appears via satellite on screens in the Shocker headquarters, and his physical whereabouts are unknown. •
Itsuji Itao as , a private taxi driver who can transform into the Inhumanoid , a field captain in the Shocker ranks who's responsible for covert assassination missions, and is behind several "mysterious" deaths prior to and during the course of the film. •
Kanji Tsuda as , a field captain in the Shocker ranks, he is responsible for the "recruitment" (abduction) of potential Inhumanoid candidates. He is the only Shocker soldier depicted as being capable of flight. •
Renji Ishibashi as •
Hirotarō Honda as •
Hitomi Nakahodo as •
Katsumi Shiono as •
Hideyo Amamoto as , also known by his real name Dr. Shinigami, the mysterious elderly man who is the figurehead of shocker. During the course of the film, he appears only via satellite on screens in the Shocker headquarters. His physical whereabouts are unknown. This was Amamoto's posthumous role after his death in 2003. • Eiji Maruyama provides the voice of Shinagami. ==Returning cast and crew==