"Parasite Dolls" is a three-episode OVA series set in a dystopian future where androids, known as Boomers, coexist with humans. The story unfolds in a world where Boomers, designed to serve humanity, occasionally malfunction or are exploited for criminal purposes. The narrative centers on the Advanced Police (A.D. Police) unit, specifically the Branch division, which handles cases involving rogue Boomers and other cybernetic threats.

The protagonist, Buzz Nikvest, is a skilled investigator working for the A.D. Police. He is joined by his partner, Gina Marceau, a humanoid Boomer with advanced combat capabilities, and their superior, Chief Reiko Michaelson. Together, they tackle cases that blur the line between humanity and artificial intelligence, often confronting the ethical dilemmas and societal tensions arising from the coexistence of humans and Boomers.

The first episode, "Sleepless Night," introduces the team as they investigate a series of murders linked to a rogue Boomer. The case reveals the darker side of human-Boomer relationships, including exploitation and abuse. The second episode, "Bloodsucker," delves into the underground world of illegal Boomer modifications, where criminals enhance Boomers for nefarious purposes. The final episode, "Reign of Darkness," escalates the stakes as the team uncovers a conspiracy involving a powerful corporation and its experiments with advanced Boomer technology, threatening the fragile balance between humans and machines.

Throughout the series, themes of identity, morality, and the consequences of technological advancement are explored. The characters grapple with their own perceptions of humanity, particularly Gina, who struggles with her dual nature as both a machine and a sentient being. The narrative maintains a focus on the procedural aspects of the A.D. Police's work while weaving in personal stakes and broader societal implications. The series concludes with a resolution to the immediate threats but leaves lingering questions about the future of human-Boomer relations.