It is a time of peace between the Earth and the Moon, in the aftermath of the great war between them. On Earth, young Asagiri Tatsuya is amazed to learn that his home is to have a Lunar exchange student, for a homestay guest. Even more amazingly, his guest is none other than the Princess of the Lunar Sphere Kingdom, Feena Fam Earthlight. As Tatsuya struggles to deal with the ramifications of this, and as tensions rise between Earth and Moon, he also learns that there is more to this homestay than meets the eye, and that he and Feena have a shared destiny...