Set in the future on a land that, after being marred by long-lasting wars, has settled into a quiet cycle of decline. Kanata Kumika is a 15-year-old girl who fulfills her dream of enlisting in the army and joins a unit of five girls who protect a fortress that looms over a little village. The girls also play music that reverberates across the skies over towns without people and seas without fish.

This title is reported as using the Spanish city of Cuenca and its nearby Alarcón Fortress as a model for the storyline.