A high school girl named Aya is incredibly curious about the mysterious "oni-san" who works at the CD shop. However, the true identity of the "oni-san" is Mitsuki, a classmate who has never spoken to Aya and is quite inconspicuous. This is a story about the "affection" between girls that has garnered immense attention on Twitter, now finally published as a book. It also includes a newly illustrated story revolving around Mitsuki's past.