Asuna is a young girl who has been forced to grow-up quickly due to the death of her father and spend her days listening to mysterious music from a crystal radio which she received as a memento. On the way to her favourite mountain hideout, she is attacked by a fearsome creature and later saved by a young man named Shun, who came from a faraway land called Agartha.<br> <br> They begin to open their hearts towards each other and Asuna promises to be back, but is not able to find Shun the next day. In school, a lecture about the mythological underworld Agartha, the land of the dead by substitute teacher Morisaki catches Asuna's attention.<br> <br> Asuna then comes across a boy that resembles her saviour at her hideout, and eventually finds out it is his brother Shin, who is being chased by a group of men after his Clavis, the key to Agartha.<br> <br> With the entrance to Agartha before her eyes, Asuna makes up her mind to see Shun once again and together, they set out on a journey into a land of legends…