The world was plagued by Shocker, a mysterious terrorist organization. For its plan in world domination, Shocker recruited agents by kidnapping people, turning them into mutant cyborgs and, ultimately, brainwashing them. However, one of the victims was rescued just before the final step, and his name was Takeshi Hongo.

With his sanity and moral conscience remaining intact, Hongo became the grasshopper-looking, altered-human (改造人間, kaizou ningen) superhero Kamen Rider and battled Shocker with his newly acquired powers.