One day a high school student Kaoru Tono hears a legend about the Urashima Tunnel. They say that if you go through it, on the other side you will get what you desire. But to obtain it you must pay with years of your own life. Soon the boy finds himself in front of a strange tunnel, eerily similar to the one about which rumors swirl. While Kaoru is thinking of his deceased sister, Anzu Hanashiro approaches him, wanting to join him to test the truth of the legend.