September 20th. Sunny. I wonder if it bugs me so much because I can't see it. I've gotten totally obsessed with finding out what's inside that bump. It's all I think about on my way to school, in the bathtub, and when I'm trying to fall asleep at night. I mean, if I could just figure out what's inside that bump, I'm sure I could figure out lots of other things too.

Beautiful as the wings of a butterfly, covered by green hills and inspired by the power of the human imagination - that is Kanuma, a cyber world created by scientists. But because Kanuma's self-developing AI began to communicate in a language unknown to humans, engineers want to delete Kanuma. One of the scientists shares the last four hours before it ends with a cyber girl who means a lot to her. Will this friendship last the end of a world?

When fourteen-year-old Yo is hospitalized she gradually develops feelings for Yayoi who is a nurse tending her. However, Yayoi leaves the nursing profession in favour of prostitution. Yo is disappointed, but turns to the older woman after she is the subject of unrequited love from her mother's man. The two grow closer and Yo is about to find out what motivates Yayoi.