星を追う子ども

Asuna Watase is a lonely girl who listens to strange music on a crystal radio her late father left her. After a creature attacks her, she is saved by a boy named Shun who says he comes from Agartha, a hidden land beneath the earth. When Shun's brother Shin and her teacher Mr. Morisaki both turn out to be drawn to Agartha, Asuna follows them underground.