The terrorist organization Shocker, seeking world domination, targets the Toyo Atomic Energy Research Laboratory in Tokyo, but their initial attack by the revived monsters Bat Man and Scorpion Man is thwarted by an impenetrable electromagnetic force field surrounding the complex. Enraged by the failure and the Japanese branch lagging behind its international counterparts, the Great Leader of Shocker orders the creation of a new cyborg soldier capable of destroying the barrier. To accomplish this, Shocker scientists abduct arrogant professional soccer player Ken Nomoto, renowned for his lethal kicking power, and surgically remodel him into Tokageron, a reptilian monster fused with lizard DNA. The narrative follows Takeshi Hongo, a brilliant biochemist kidnapped and transformed by Shocker into a grasshopper-themed cyborg who escaped and now fights as the heroic Kamen Rider. Allied with his mentor Tobei Tachibana, the professor's daughter Ruriko Midorikawa, and the hot-headed Kazuya Taki who is secretly an FBI agent, Takeshi must stop Shocker from detonating a five-kilogram bomb that would destroy the laboratory and devastate Tokyo within minutes.

As Tokageron and the newly revived Monster Corps, which includes the ten cyborg assassins previously defeated by Kamen Rider, scout the laboratory for weaknesses, Taki investigates a suspicious house only to discover a room filled with seemingly lifelike statues of past Shocker monsters that are actually the dormant Revived Monster Corps awaiting orders. When Tokageron overpowers Kamen Rider in their first encounter using his soccer-based attacks, Takeshi retreats to train intensively at Tachibana's former racing grounds, developing a new technique the Electric Ray Rider Kick to counter Tokageron's abilities. The story culminates in a final confrontation at the laboratory where Kamen Rider, now wielding his enhanced attack, intercepts the bomb mid-flight, deflects it back at Tokageron, and battles all eleven Shocker monsters simultaneously. The resulting explosion destroys both the bomb and the monster army, securing victory for Kamen Rider who then departs, vowing to continue protecting Japan from Shocker's ongoing schemes for world conquest.