The narrative centers on the two titular girls, Escha and Chron, whose contrasting personalities are likened to the sun and moon. Both girls originate from Terminal, a future post-apocalyptic world that is empty and monochrome. They cross worlds and arrive in the present day, which they refer to as Transit. As Escha and Chron experience the light (scenery) and sound (music) of the real world, the future world of Terminal gradually transforms into a more vivid place.