The ruler of the alternate dimension empire, Dark Idea, devises a cunning brainwashing operation to capture Kuroki Ai, the cosmic detective known as Angel Heart who protects Earth, and transform her into the empire's empress. This scheme includes the abduction of two of Ai's closest friends, whom he converts into his loyal subordinates—Dark Angels—through an evil transformation process. Under Dark Idea's orders, the two Dark Angels capture Ai, subjecting her to a brainwashing device and preparing to fully dominate her. During this process, Ai witnesses her friends' twisted metamorphosis, descending into frenzied madness before Dark Idea. Shaken and overwhelmed, Ai struggles against the brainwashing machine's intense electromagnetic waves, but ultimately succumbs to the relentless torment inflicted by the Dark Angels, finally awakening as Dark Angel Ai. Her new form radiates overwhelming aura and charisma, allowing her to dominate the other two Dark Angels. Yielding to her own desires, she pledges eternal loyalty to Dark Idea, craving his body and semen.