Seeking revenge for the murder of his close friend and mentor, Goro Numata, a young man named Shigeru Jo makes a dangerous decision. He voluntarily infiltrates the evil organization Black Satan, the very group responsible for the killing, and pretends to pledge his loyalty. Driven by a thirst for vengeance, he undergoes a brutal surgery to be transformed into a powerful cyborg warrior. However, Shigeru secretly resists the brainwashing process, and once the operation is complete, he reveals his true intentions, denounces Black Satan, and escapes from their headquarters as the electric-powered hero Kamen Rider Stronger.

During his escape, Shigeru rescues another captive, Yuriko Misaki, who has also been forcibly transformed into a cyborg known as the Electro-Wave Human Tackle. Together, the two newly created beings form an alliance against their creators. They are soon joined by Tobei Tachibana, a wise mentor who has aided previous Kamen Riders, and together they fight to stop Black Satan’s campaign of world domination. The early battles pit Stronger and Tackle against the organization's top commanders: the brutish One-Eyed Titan and the cunning, sword-wielding General Shadow, whose intense rivalry often hinders their efforts to destroy the heroes.

The first major arc concludes with Stronger successfully dismantling Black Satan. However, General Shadow survives the fall of his organization and immediately forms a new, more formidable threat known as the Delza Army. The warriors of the Delza Army prove to be far stronger than their predecessors, pushing Stronger to his limits. In a desperate battle against one of the Delza Army's generals, Doctor Kate, Tackle is fatally poisoned. To protect Shigeru and ensure the villain is defeated, she makes the ultimate sacrifice, using her life force to destroy Doctor Kate.

Consumed by grief and a renewed sense of purpose, Shigeru undergoes another risky procedure to enhance his own cyborg body. This grants him a powerful but time-limited new form: Stronger Charge Up. With this increased power, he is able to turn the tide against the Delza Army. In the series' final arc, the threat escalates to a global scale, prompting the previous six Kamen Riders—Ichigo, Nigo, V3, Riderman, X, and Amazon—to return to Japan. Uniting all seven heroes, Stronger and his predecessors launch a final, all-out assault that destroys the Delza Army and its mysterious Great Leader once and for all.