Using "first type" androids, humans began terraforming the unfriendly environment of Mars and built the city of Saint Lowell.

Ross Sylibus, a middle-aged policeman from Chicago, travels to Saint Lowell to meet his new partner Naomi Armitage.

As Ross exits the shuttle, he bumps into a mysterious man with a big suitcase and two robotic guards, and Armitage orders the men to stop.

To everybody's surprise and horror, McCanon turns out to be a robot: a new, never-seen-before "Third type" android that is superficially identical to humans.

The mysterious man, René D'anclaude, reveals that the Third types have been among the regular people for a long time and nobody can tell them apart from humans.

While the police drop the case with D'anclaude's supposed capture, Armitage and Julian search a databank for information on her origins.

Armitage and Ross later go off in search of her "father", Dr. Asakura, only to learn he had lost his mind, as explained by a gentler, reprogrammed version of D'anclaude, living with delusions of creating "Fourths".

They learn that the Thirds were originally "assassinroids" - deadly robots with organic components, capable of infiltrating secure facilities by masquerading as humans.

These revelations shock and dismay Armitage, leading her to seek comfort in Ross, who affirms her value as a living being before consummating their relationship.

When Armitage arrives on Earth, she confronts Colonel Strings, hero of the First Error, which was a suppression of a robot uprising, which in reality, was to cover up the existence of the Thirds.

Its vice president, Demetrio Mardini, asks Armitage to give the data on how Thirds can conceive so humanity can create a race of beings who exist to serve.

She then escapes but is damaged and is found by a repairer third named Mouse, who prides himself on his skill and frequently brags that he's a "genius".

Back on Mars, prime minister Fredrick O'Hara sends Ross to Earth to represent the planet in the support of robot rights, promising amnesty from the charges against them.

It is here that Yoko shows that she has a photographic memory, leading them to the space elevator whose location she determined from a map she saw minutes beforehand (Ross comments that she is "quite a genius").

He tells her that the password is "Heaven's Door"; but that if she exceeds more than her internal battery can handle, she will "be knocking at the Pearly Gates for real".

Pioneer USA released an English-dubbed version of the OVA series in VHS & LaserDisc format in North America in four volumes, each containing a single episode, between March 29, 1995, and December 5, 1995.

She praises the design and scripts, while saying that the "basic plot is simply a retelling of Pinocchio - the toy that wants to be real, or, in science fiction terms, the robot yearning for love and acceptance as a person, not just a product".