The series is set in a world ravaged by Shocker, a mysterious global terrorist group composed of surviving Nazi members. To advance its scheme for world domination, Shocker abducted individuals, transforming them into mutant cyborgs and, finally, brainwashing them. Yet, one victim, Takeshi Hongo, escaped moments before the final brainwashing. Retaining his sanity and moral compass, Hongo fought against Shocker's henchmen as Kamen Rider, a superhero with a grasshopper motif.