Naomi Tanizaki is an office staff at the Armed Detective Agency and the younger sister of Jun'ichirō Tanizaki. Naomi is a high school-age girl with hip-length black hair that is styled in a side-swept hime cut and dark grey eyes. She also has a beauty mark underneath her left eye. In general, her appearance does not resemble her brother, given her charismatic allure compared to Tanizaki's timid disposition. She wears a standard seifuku that consists of a white long-sleeved blouse attached with a red sailor-style collar and a black pleated skirt that comes above her knees. She also dons black socks that reach the middle of her calves and a pair of brown loafers. During the aftermath celebration of cannibalism events, Naomi wears her hair in a high bun. She also wears a sky blue dress with white top over it. She also wears heels. Naomi is a bold and strong-willed young girl, who never shies away from involving herself in a case—more specifically, ones that involve her older brother's well-being. Despite not being an ability user, she is often embroiled in the Agency's conflict, but when told to leave, she mostly refuses. As an Agency clerk, Naomi is rather intelligent and quick-thinking, even amidst perilous circumstances. She is also shown to be mentally resilient because, in spite of being a near-frequent victim to kidnappings and ability users, she takes it quite well and is outwardly unaffected. Moreover, she appears to be courteous towards Agency clients, as shown when she professionally served Francis Scott Key Fitzgerald some tea, though she retained some subtle hostility towards their adversary similar to the President at the time. Probably one of Naomi's most prominent characteristics is her deep-seated love for her elder brother, whom she is always with. When with her brother, she can be both childish and provocative. Her feelings seem to go beyond that of ordinary sisterly love and can be seen as romantic in nature due to a number of questionable circumstances and suggestive remarks, to the point that the Agency keeps silent on their relationship "for fear that their hunch was right". However, be it romantic or platonic, Naomi remains unwavering in her devotion and belief towards her brother and does what she can to protect him from harm's way, even shielding him with her own body from Ichiyō Higuchi's gunshots. Besides her brother, Naomi is also kind and caring towards the other members of the Agency. She visibly shows concern when the others were contemplating abandoning Atsushi Nakajima during his kidnapping and easily forgives him when he falls victim to Dogra Magra that caused him to lash out on her and Kirako Haruno with his powers.