It is winter, just before February, when Misato Juri discovers a strange, beautiful butterfly in the garden of his apartment. Its lustrous lapis-blue wings are cruelly shriveled, leaving it unable to fly, so Juri names her “Ao” and takes her in. The next day, he returns home to find an unfamiliar girl collapsed in his room. Wearing a dress patterned with familiar lapis-blue wings, she introduces herself as Ao, the butterfly he saved, and reveals that she possesses an infallible ability to predict the future. As thanks for saving her, she reads Juri’s fortune and gives him a shocking prophecy: he will die in nine days.

Ao’s sudden transformation raises more questions than answers. Why did the butterfly become human? What is the source of her ability to see the future? And can Juri somehow escape the fate she has foretold? With only nine days remaining, Juri must uncover the truth behind Ao and the mysterious connection between them before his time runs out.