In the hushed-up war against Saint, mankind has been saved countless times by an android named Andou Mahoro. After her last battle, Mahoro discovers that if she stays in her full battle mode, she only has a limited lifespan left to her. If her armaments are removed, Mahoro has a new lease on life and the freedom to live it as she pleases — for another 398 days at least. So what should an android with a little over a year left do? Misato Suguru, a 14-year-old orphan, hires Mahoro on as a maid. Poor Suguru has no idea of Mahoro's past life, or her deep connection to him. But he is not one to complain as Mahoro moves in. His friends find this suspicious though, and his homeroom teacher Shikijou Saori becomes rather jealous. Now Suguru just has to come to terms with the fact that his beautiful maid is actually only 9 years old and an android!