It appeared in the Period 37: The Witch of the Library Room.
A black book with The Charm written above a pentagram. A single line traces the cover, and on each corner is a triangular piece. The pages of the book are white and contain many words and drawings.
Riri Itou and her friends first heard about the book during their visit to the library in search of a sewing book. A girl had been discussing it with her friend, saying it had been included among the picture books and various other things the school obtained during a trade. A student found it and translated the book, then she proceeded to test it out by seeing if a boy she had feelings for would like her. When she did, she found out she could use the charm on others with the same results. Riri had become inspired by this, wondering if she could possibly use it on Hijiri; a boy she and her friends adored.
Midway through the story, Riri came to believe her friends, Mako and Misao had been the cause of the life-threatening misfortunes befalling her. She attempted to find the book, but was unable to and eventually came to believe they probably hid it back in the library from her. She headed back to it to check and soon found a girl holding it. She handed it over, revealing that another student had just dropped it off; leaving Riri to realize her friends couldn't have done it as she had just left them. She was shocked to find out Hijiri had been the person who last checked it out- but before she could react she had been crushed by the bookcase behind her.
Hijiri revealed the misanga he made for himself had been from the Witch's Book. It had a talisman-like charm placed on it to protect him from evil and danger.