When he wakes up, Setsuna has no memories. He is on the island left behind by time, Urashima. Everyone he meets is mysterious and puzzling. At night he is surprised by a girl singing on the beach, and somehow says her name.

Setsuna begins to research soot blight syndrome to understand the shocking statement Rinne makes. The endemic disease keeps the island isolated and toys with Rinne, Karen and Sara’s fates. But Rinne’s mother Kuon knows something unexpected.

Setsuna, Sara and Karen try various ways to get Rinne to come out during the day. Their fun time is interrupted when Rinne sees a hidden shack. After that, Rinne tries to stop thinking about the past, but Karen makes a decision to face it down.

Although it was by Karen’s request, Setsuna does something unthinkable. They go to the mainland so that Karen can escape and go to see her mother. Why did she cry while Setsuna watched over her? Meanwhile, Sara is getting close to something.

Sara has a hypothesis as to why Setsuna came back in time and believes they are destined to be together, but Rinne confronts him with a dark truth. Crimson flames lick the heavens, bringing an end to a bloody history.

The darkness has lifted for Karen and Sara. Rinne has prepared herself to bid farewell to the past and set off toward tomorrow, but Kuon seems to have misgivings.