A forty-year-old construction worker named Tanzaburo Tojima has held onto a single dream since childhood: to become a Kamen Rider. Even after realizing the television series is fictional and the evil organization Shocker does not exist, he has never stopped training his body in the mountains, preparing for a moment he knows may never come. As he is about to sell off his precious collection and finally give up, a wave of robberies committed by criminals dressed as Shocker sweeps through the city. On impulse, Tanzaburo buys a cheap plastic Kamen Rider mask from a festival stall, puts it on, and rushes to confront the so-called Fake Shocker. Instead of being hailed as a hero, his clumsy but earnest effort is filmed and turned into an internet laughingstock. Undeterred, he decides to investigate the crimes for real, taking to the streets as his own version of Kamen Rider.

Tanzaburo soon discovers he is not alone in his obsession. Yuriko Okada, a twenty-four-year-old high school teacher, has modeled herself after Electro-Wave Human Tackle, the first female hero from Kamen Rider Stronger, and trains relentlessly to honor her. The Shimamura siblings bring deeper experience: Ichiyo, thirty-two, witnessed Shocker monsters murdering his grandparents as a child and has since dedicated his life to embodying Kamen Rider V3, while his younger brother Mitsuba, twenty-seven, takes up the mantle of Riderman, complete with a homemade replica helmet and functional Rope Arm. Together, this unlikely group of adult fans begins to uncover a terrifying truth. The Fake Shocker crimes are a front, but the real Shocker also exists. Its monsters, including the mysterious Spider Man and the brutal Bat Man, operate in the shadows, converting humans into brainwashed Combatants and pursuing a sinister agenda.

Over the course of the series, the group faces escalating threats that test both their physical limits and their resolve. They hold a tournament to determine who among them is the strongest Kamen Rider, only to realize that their infighting distracts from the real enemy. Tanzaburo finds an unexpected ally in Hachiro Nakao, a forty-four-year-old yakuza who initially led the Fake Shocker robberies out of admiration for Shocker. After being killed and resurrected as a Combatant, Nakao breaks free of brainwashing and joins the heroes, developing his own fighting technique called the.44 Magnum. The group also contends with Yukarisu, a Shocker spy sent to watch Mitsuba who genuinely falls in love with him and defects, and Futaba Shimamura, the middle sibling who resents Ichiyo for driving their family apart but is forced to acknowledge that Shocker is real.

As the story progresses, the Bat Man emerges as a major antagonist, taking over multiple idol groups to indoctrinate fans and convert them into Combatants through his bite. He targets Nakao and his underlings, as well as the Shimamura siblings, seeking revenge for past defeats. Thunder Raiko, a former professional wrestler turned elite Shocker Combatant, hunts down defectors and pushes the group to its breaking point. Tanzaburo experiences his first retreat from a fight, prompting a deep crisis in which he questions whether he has any right to call himself a hero. Through rigorous training, painful losses, and the unwavering support of his friends, he rediscovers that the source of a Kamen Riders strength is not a transformation belt or superpowers, but an unbreakable sense of justice.

In the final battle, Tanzaburo confronts the real Shocker forces without any special equipment beyond his worn plastic mask and his well-trained body. He faces the Shocker Combatman in a rain-soaked alley, trading blows that tear his suit and leave him bloodied but still standing. Yuriko fights alongside him, injured but defiant, and together they overcome the monsters that have terrorized the city. Tanzaburo lands a final Rider Punch that destroys the Combatman, bringing an end to Shocker's active threat. Afterward, he retires his suit, hanging it in his cluttered apartment among the Kamen Rider posters of his youth. He returns to his ordinary life as a construction worker, no longer chasing a fantasy but content in having lived it. The series closes with Tanzaburo walking into the sunrise, his scarf fluttering behind him, a true Kamen Rider in spirit if not in name.