Father-and-son detectives, Sanada Kenji and Sanada Shun, fall into a trap while tracking the villain Buglar. Buglar is an androgynous criminal obsessed with beauty, indifferent to gender. Taking Kenji hostage, he torments Shun, leaving him helpless. Witnessing this, Kenji summons all his strength, pushing himself to the limit to help Shun escape. While fleeing, Shun transforms into the crossdressing heroine Metalwoman to save his father. Though Shun rescues Kenji in his Metalwoman form, his true identity is exposed to Buglar. Buglar then kidnaps Kenji and brainwashes him, luring Metalwoman into a trap and forcing the brainwashed Kenji to attack him.