Mahoromatic: Automatic Maiden

Mahoro, a powerful battle android, fights alongside Vesper, a secret agency taking on an alien army. With limited operating time left, Mahoro's lifespan can be extended to just over a year by conserving her power, but she'd have to stop fighting. Instead, she chooses to live the remaining time as a maid for Suguru, a middle school student who lives alone after his family passed away.