Urashima is an island far from the mainland. The people who live there lead carefree lives. But five years ago, the island's three great families suffered a series of misfortunes, and succumbed to suspicion. The people of the island cut off all contact with the mainland, and began a slow decline. One day, a young man named Setsuna washes ashore claiming to be a time-traveler and suffering from amnesia. He meets three local girls: Sara, Rinne, and Karen. Their meeting will change the course of the island's fate.