Tsuki no Sango takes place in approximately the year 3000, when humankind arrived at the peak of its civilization, but is losing its will to keep living. The story follows a girl, called "princess" by those around her, living on a small island with a fifty-person colony and a shining coral reef. She is a descendant of the Moon people, and it focuses on how her ancestor supposedly came to Earth.

The story is about a witch named April with the power to turn lies into reality. Due to this terrifying power, April is confined in a small house. However, once a year on April 1, April opens the door to her house to visitors. (Source: Tsuki-kan)