A book rental shop in Gensokyo. Today, Kosuzu Motoori, who was tending to the store, was looking at a book with a quizzical look on her face. It was a book that even she, who is familiar with demon books with mysterious powers, had never seen before. Making sure no one was around, she stroked the cover with her finger. Bukku...BOOKING? I might as well read it anyway." Kosuzu sits down on a chair and opens the book. Unaware that this was the beginning of something strange that would affect all of Gensokyo.