The school festival has successfully come to an end, but Yumi can't relax and is suffering from lack of sleep. She starts to seriously think about her younger sister... and while pondering, Yumi falls asleep in the Rose Hall. When she wakes up, Sachiko has left a note saying, 'I'll be going to the library,' and has disappeared. Thus begins the library hide-and-seek between Yumi and Sachiko, a mysterious special story surrounding books.