"Armitage III" is a four-part original video animation (OVA) series set in a futuristic world where humanity has colonized Mars. The story explores themes of artificial intelligence, identity, and the ethical implications of advanced robotics. The narrative centers on Ross Sylibus, a former Earth police officer, who is transferred to Mars after a traumatic incident. Upon arriving, he is partnered with Naomi Armitage, a skilled and assertive detective. Together, they investigate a series of murders targeting "Third-Type" robots—androids indistinguishable from humans, designed to perform specialized roles in society.

The murders are initially dismissed as the work of anti-robot extremists, but as Sylibus and Armitage delve deeper, they uncover a more complex conspiracy. The Third-Type robots, including Armitage herself, are revealed to possess advanced emotional and cognitive capabilities, blurring the line between machine and human. The investigation leads to the discovery of a covert project aimed at creating a new generation of androids capable of reproduction, challenging societal norms and raising questions about the future of humanity and artificial life.

Armitage’s true nature as a Third-Type android becomes a central focus, as her existence threatens powerful entities invested in maintaining the status quo. The series explores her struggle for acceptance and self-identity in a world that views her kind as disposable. Sylibus, initially skeptical of robots, develops a deep bond with Armitage, questioning his own prejudices and the ethical boundaries of artificial intelligence.

The plot escalates as the duo faces off against corporate interests, political corruption, and violent extremists. The climax reveals the extent of the conspiracy, involving the suppression of Third-Type technology to preserve human dominance. Armitage’s role as a prototype for a new era of androids positions her as both a target and a symbol of hope for a future where humans and machines coexist.

The series balances action, mystery, and philosophical inquiry, with a focus on the evolving relationship between Sylibus and Armitage. Their partnership drives the narrative, highlighting themes of trust, loyalty, and the search for meaning in a technologically advanced yet morally ambiguous world. The story concludes with an open-ended resolution, leaving room for interpretation about the future of humanity and artificial life on Mars.