A physicist named Tetsuo Okita discovers a new, highly dangerous mineral called Satanium, which possesses power beyond that of uranium and emits destructive effects on anyone exposed to it. The evil global organization Destron, seeking to conquer the world, abducts Professor Okita to force him to reveal the source of this deadly mineral so they can collect more of it. This event forces the transformed hero Shiro Kazami, as Kamen Rider V3, into action. He must race against time to rescue the professor and stop Destron from acquiring the Satanium, which would give them an unstoppable advantage in their quest for global domination.

The story takes place within the ongoing war between Destron and Kamen Rider V3, a young man who became a cyborg superhero after his family was murdered by the organization. Created by Kamen Riders 1 and 2, V3 possesses numerous special abilities and his own motorcycle, the Hurricane, to fight his mechanized enemies. The setting is primarily contemporary 1970s Japan, where Destron maintains secret bases and conducts terrorist operations.

In this specific confrontation, Destron deploys several of its Mechanical Army kaijin, including Lens Ari, Pickel Shark, Drill Mogura, Jishaku Inoshishi, Gama Boiler, Burner Koumori, Missile Yamori, Spray Nezumi, Kusarigama Tento, Guillotine Zaurus, Dokubari Gumo, Taiho Buffalo, and others, to achieve their objective. As the battle intensifies, Kamen Rider V3 finds himself facing overwhelming numbers of Destron soldiers and monsters under the command of Doctor G, Destron's German general who oversees the Japanese division. Realizing he cannot succeed alone, V3 receives crucial assistance from the original Kamen Riders, Takeshi Hongo (Kamen Rider 1) and Hayato Ichimonji (Kamen Rider 2), who join forces with him to turn the tide against the Destron forces. This alliance of three Kamen Riders represents a significant narrative arc, demonstrating the enduring legacy of the original heroes supporting their successor against the resurrected threat of Destron, which rose from the ashes of the previous evil organizations Shocker and Gel-Shocker.