Mahoro was created with artificial intelligence making her nearly human, aside from the super human abilities bestowed by her artificial body. Her purpose was to stop the invasion, and it was Mahoro that single handedly turned the tide and fought back to the point of a stalemate.

Time passed by with many battles between Saint and Vesper. Neither gaining an upper hand, and thanks to a well orchestrated cover up - civilians were none the wiser that that aliens even existed. While Mahoro was created for battle, it was her cheerful charming personality that endeared her to the people at Vesper, although thinking like a human also has its concequences. During one battle Mahoro came face to face with her "human personality" conflicting with her android intellect, when she was forced to choose between destroying a missile instilation (and indirectly killing Commander Misato), or save him and let millions to die at the missiles launched by Saint. Mahoro took the logical choice, but would have to bear the burden of her conscience for the rest of her life.

Years would pass after the incident, with Mahoro at the front fighting against Saint. Eventually Mahoro was informed that she was nearing the end of her operational life, and that she had a limited time before she would shut down. However if Mahoro would retire from combat, that her operational life would extend by a couple hundred days. With her distinguished service, Mahoro was encouraged to go into retirement. But Mahoro had always lived a life of service; and it was all she really knew, so to her a retirement of inactivity was out of the question. So Mahoro was transferred into the housekeeping division of Vesper and given a job as a maid.

Around the same time that a young 14 year old boy was looking for a maid to clean house. It would certainly be nice to have a nice old lady to help clean his house, and maybe keep him company since he lived alone. Of course when an extremely cute young girl named Mahoro showed up, Suguru was a bit unsure. Especially with the entire "I'm an android that used to fight aliens" thing. Yet for some reason things felt right with Mahoro, and Suguru decided to keep her on board. Of course things didn't go as smoothly as planned. It looks sort of... suspicious having a young pair of hormonally charged teenagers living together. Aside from that Mahoro takes the ideal of being a maid WAAAY to seriously. Still, Suguru couldn't remember the last time he had been so happy.

But there are secrets that Mahoro still hasn't revealed to Suguru. He still doesn't know that her life will terminate in about a year. He also doesn't know that his father used to work for Vesper and it was Mahoro who was responsible for his death. Can Mahoro; who was the single most important weapon the Earth had fielded against the aliens, simply retire or will her past catch up to her? These facts lurk constantly in the back of Mahoro's mind, but to her commander Misato was like a father, and she owes it to him, and his son to at least TRY to make amends for what she has done - even if it was the logical thing to do...