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.

When they awoke, they were looking up at the blue sky from five years ago. It was the mysterious island where Rinne and the real Setsuna had been before parting ways forever. Rinne feels excited to see the real Setsuna again and finally settle things, but what they find are more riddles, tears, and darkness.

Setsuna rises up to create a future for a city without hope, but tragedy strikes time and again. Meanwhile, Rinne finishes her invention and Setsuna sets out for the future to save mankind's existence. Just before he goes, Setsuna makes a promise to Rinne.

Rinne and Rinne - A truth about these two girls is brought to light by a photograph, and Setsuna makes a decision. Will it make everyone happy? A new future awaits once this great mystery is solved. No more hesitating. It's the eternal finale.