Setsuna Sanzenkai washes up with no memory of how he got there on Urashima, an island where three founding families have been in decline since a shared misfortune struck them five years earlier. Taken in as a servant by Rinne Ohara, and later drawn into the orbit of the shrine maiden Sara, Setsuna claims to be a time traveler trying to change the island's fate, a claim the wary islanders aren't ready to believe. This manga adapts Frontwing's mystery visual novel of the same name, following Setsuna as he tries to prove himself to a community that doesn't trust outsiders.