The main plotline concerns retired Mr Ueno, who since a child has been cared for by his late parents’ robot maid ‘Maria’ – a lifelike humanoid in a maid’s outfit! Over the years, Ueno has developed an unconsummated love for Maria, but although she has not ‘aged’ as such, she is now classed as an obsolete model and Ueno is finding it difficult replacing her fading battery… The secondary plotline involves Detective Yuri Akagi, who is investigating a series of rapes, which she believes may be being committed by a rogue droid.

Maria has been gifted to a college student, Akiba, by his academic mentor Yoshiyuki, who has died under suspicious circumstances. Little does Akiba known that Maria has been reprogrammed by Yoshiyuki to do battle against the evil Host-Droids – male robots designed by a rival robotics company to take revenge on the female species.