Kaori Nonomiya is a first-year student and library committee member. She stands 151 cm tall with a slim build and measurements of 75-51-78 cm, featuring short brown hair, amber eyes, and consistent attire of glasses paired with a hair ribbon. Her school uniform typically includes a skirt and over-the-knee socks. In the library, she enforces silence rigorously, wielding the thick medical reference "Home Medicine" as a threat against disturbances. Outside these duties, she exhibits a quiet, bookish demeanor, preferring solitary time among books.

Academically, she excels in literature-based subjects—modern Japanese, classical literature, and Chinese classics—but struggles with and dislikes mathematics, physics, chemistry, and physical education. Her dietary preferences favor omelets while avoiding foods with animate appearances. Privately, within the library, she harbors unexpressed romantic and sexual fantasies about an older male student, Tomohiro Takabe. Mina Hayase's involvement with Tomohiro fuels Kaori's persistent internal conflict and unresolved emotional turmoil regarding him.