There is a war being fought, of which most of the Earth's population is totally unaware. Vesper is a secret agency fighting an army of alien invaders by using super-powerful battle androids. Mahoro is Vesper's most powerful battle android and has won many battles, but she has little operating time left and soon will cease to function. However, if she lays down her arms and conserves her remaining power, the time she has left can be prolonged to just over a year.

Mahoro is given an opportunity to live the remaining time she has as a normal human. She chooses to live among the humans as a maid. She eventually settles in with Suguru, a phenomenally messy high school student who lives by himself after his family passed away. Because Mahoro has little knowledge of the world outside the battlefield, she learns about these things through her interactions between Suguru and his classmates (and a rather annoying but well-endowed teacher).

There is a war being fought, of which most of the Earth's population is totally unaware. Vesper is a secret agency fighting an army of alien invaders by using super-powerful battle androids. Mahoro is Vesper's most powerful battle android and has won many battles, but she has little operating time left and soon will cease to function. However, if she lays down her arms and conserves her remaining power, the time she has left can be prolonged to just over a year.

Mahoro is given an opportunity to live the remaining time she has as a normal human. She chooses to live among the humans as a maid. She eventually settles in with Suguru, a phenomenally messy high school student who lives by himself after his family passed away. Because Mahoro has little knowledge of the world outside the battlefield, she learns about these things through her interactions between Suguru and his classmates (and a rather annoying but well-endowed teacher).