Society was stunned by a case of serial bombings. Raito Shiba, a detective who exclusively handles superhuman cases, gets suspicious that there is nothing left behind at the scene. Raito guesses that employees of the military corporation Yatsuka Heavy Industry were attacked, and investigates the factory in Tachikawa. Then at a nearby park, he meets a girl named Mieko in a schoolgirl uniform. When the conflict worsens with the "Superhuman Bureau," which he has seen as an enemy for long, the surprising secret about Mieko comes to light. Raito, who had his life taken away by an evil organization and was made into a machine body, starts to get complicated feelings in his mind.
Haneda Airport recovers from what seems like a terrorist bomb attack, though no threat or demand was sent. Detective Shiba suspects superhuman involvement, but all the evidence is taken from the Tokyo Metropolitan Police by the Superhuman Bureau, so Shiba tries following a lead to Yatsuka Heavy Industries. Along the way, Shiba meets a girl named Mieko, but quickly discovers that she is a robot as the Superhuman Bureau intervenes and Shiba is caught in an explosion. While Shiba recovers at the Bureau, Professor Hitoyoshi mentions that Mieko was the "female" half of a human-looking robot pair, programmed to seek out a "male" counterpart to form a large explosive in enemy territory. Jiro wants to capture Mieko alive, but Shiba and others at the Bureau want the robot dead before she explodes in a populated area. Despite Jiro's efforts, Shiba takes matters into his own hands, but Mieko decides to jump into a nearby reservoir and self-destruct without killing anyone.
Five years later, Shiba attacks a military truck escorting a male prisoner and frees him. He discovered that the man was the male robot of the pair, and that Mieko did not actually self-destruct but merely slept at the bottom of a reservoir before it was drained for the sake of urban development. Shiba commands the male robot to merge with Mieko for the sake of his terrorist plot, until Jiro appears and inserts a chip into her frame. As the male and female robots merge, they decide not to follow Shiba's command. Enraged, Shiba beats up the merged robot, and then turns his anger on Jiro.