Shin grows up underground in the legendary land of Agartha, a world from which no stars are visible, looking up to his gifted older brother Shun and sharing his longing for the surface. That longing eventually splits the brothers apart: Shun leaves for the world above carrying a crystal, and Shin follows to bring it back. Up there he crosses paths with Asuna, a girl who has grown up without her father, and Morisaki, a man who has been searching for Agartha since his wife died. This two-volume manga tells the Children Who Chase Lost Voices story from Shin's side.