Mahoromatic

Suguru Misato, a young teen boy living by himself since his parents have passed away a few years ago, decides to hire a maid to help clean up his house. Enter Mahoro, a former combat android created to defend the Earth against a secret alien invasion in the early 1980's. Given the choice of continuing in her service for Vesper and functioning for a mere 37 days or retiring, giving up her combat armor and continuing to function for 398 days, Mahoro has chosen to serve as a maid to one Suguru Misato.