Tsuki no Sango

Tsuki no Sango summary:

The story takes place in approximately the year 3000, when humankind arrived at the peak of its civilization, but is loosing it's will to keep living. It follows a girl, called "princess" by those around her, living on a small island with a fifty person colony and a shinning coral reef. She is descendent of Moon people, and it focuses upon how her ancestor supposedly came to Earth.