During a playful moment with his son, Hiroshi Nohara injures his back and, in a bid for relief, agrees to a spa visit that takes an unexpected turn: he is transformed into a robot, turning the family’s quiet life upside down.
Back at home, his wife, Misae Nohara, watches the strange behavior with growing concern and hires private investigator Teruyo Dandanbara to uncover the spa’s secrets. Her suspicions deepen when Hiroshi, now in robotic form, proves his protective side by rescuing Shinnosuke Nohara and his friends during a field trip, showing that beneath the chrome exterior there remains a father who still cares.
The mystery takes a darker turn when Omega Ranran, who had invited Hiroshi to the spa earlier, supplies him with a mustache add-on. Once plugged in, Hiroshi’s robot persona sharpens into a furious, antifeminist crusade that rails against what he sees as fathers’ grievances. Shin-chan and his friends work to remove the mustache, but Hiroshi is soon captured by Tekkenji Doukatsu, Ranran’s fearsome leader, pulling the family into a dangerous chain of events.
Shin follows Hiroshi to Tekkenji’s factory, where he discovers Hiroshi in his human form; the robot version turns out to be a memory-bearing clone of Hiroshi. With this new understanding, Shin-chan and both versions of Hiroshi rally to halt the campaign, and the robots prove their mettle as Hiroshi’s human will and memory guide their actions to overpower Tekkenji’s forces.
The plot thickens as the Nohara family and Teruyo are captured by Tekkenji, who is revealed to be a robot controlled by police chief Jintaro Kuroiwa. Kuroiwa attributes his own misogynistic attitude to years of abuse and neglect from his wife and daughter, a backstory that complicates the struggle between control and autonomy. In a cruel ploy, Kuroiwa attempts to force Shin-chan to eat green bell peppers using Hiroshi’s robot—an act Shin-chan foils by breaking the forced control and turning the tide.
From the ruined base to the field trip site, a brutal battle rages, pitting human and robotic versions against a tyrannical regime. Shin-chan and the two Hiroshis unite against Kuroiwa, turning the odds in their favor. The showdown culminates in an arm-wrestling contest between Hiroshi and his robot double, where the human version emerges victorious and the robotic replica collapses from its wounds.
In the end, the conflict resolves around identity, family, and resilience. The real Hiroshi proves that love and humanity can pierce through even a mechanical exterior, while the clone’s demise reinforces the message that memories and meanings rooted in care cannot be wholly replaced. The Nohara family, bolstered by Teruyo’s dedication, steps back into their everyday life with a renewed sense of togetherness, knowing that truth and trust endure beyond any chrome facade.
