"Do you know the Urashima Tunnel? It is said that as long as you enter that tunnel, you can get anything you want; but in return, you will get older─" High school student Kaoru Tano heard about this urban legend, and happened to find the tunnel that was suspected to be mentioned in the rumor that night. ──As long as you enter this tunnel, you may be able to save your sister who passed away five years ago. After school, Kaoru began to explore the tunnel alone, but was discovered by the transfer student Kyoko Huacheng. The two work together to get what each other wants, but... A surprising summer filled with unprecedented experiences is about to begin──
Purpose: To find the lost self, courage and determination in the confusion of youth.