Rotten Girl is a female employee of the Horse's Bone bookstore. She received her nickname "Rotten Girl" not because she is a fujoshi/yaoi fan as the name would imply, but because she's a huge fan of zombie media. Rotten Girl is obsessed with zombies to the point of sometimes attacking others whenever they display zombie-like behavior. She frequently pairs up with Sommelier despite the glaring difference in height. Appearance-wise, she is short and has short red hair. She is still in high school and lives together with her family.

Spoiler

Her real name is revealed to be Haru, the older sister of Taishi Yatsu who attacks Umio one day at work.