Mei Nakayama is a 20-year-old woman with brown eyes and shoulder-length straight brown hair styled in a side-parted bob cut. She stands 157 centimeters tall, weighs 42 kilograms, and possesses a slim build with pale skin and body measurements of 81-55-84 centimeters, including a B-cup bust. Her typical attire includes glasses, earrings, a dress shirt, and a skirt.

She works as a secretary and personal assistant to private detective Satoru Kido, efficiently managing office duties and aiding his investigations. Her compensation involves irregular, unconventional methods instead of formal paychecks, a situation she accepts despite its inconsistency. An orphan and university student, Mei displays tsundere traits, often starting with sharp or dismissive behavior that may soften contextually. She drives pivotal decisions, such as convincing Kido to take a protective assignment at a client’s mansion after his initial refusal. This case centers on a missing jewel and concealed family secrets.

Her character remains consistent with this established role in additional seasons, movies, or spin-offs, without significant development or expanded background.