Nanase Kotobuki is a second-year student at Seijoh Academy who works as a student library aide. She has bleached brown hair and an excellent figure, traits contributing to her popularity. Her communication style is characteristically brisk and harsh, serving as deliberate armor to conceal her genuine emotions and vulnerabilities.

She first observed classmate Konoha Inoue from afar during junior high, perceiving his happiness—especially around Miu Asakura—as authentic. Reuniting with him in high school, however, she discerned a marked shift in his personality, interpreting his consistent kindness as disingenuous. This perception fuels her outward hostility, masking her longstanding romantic feelings. Her inability to express these emotions results in repeated misunderstandings that suggest animosity toward Konoha.

Her struggle to communicate her affection forms the core narrative in "Bungaku Shōjo Memoir III - Koi Suru Otome no Rhapsody." Her closest friend, Kurara Mori, recognizes Nanase’s true feelings and intervenes to bridge the misunderstanding. Their comedic yet earnest attempts to convey Nanase’s emotions often backfire, including one misadventure culminating in hospitalization.

Despite briefly becoming Konoha’s girlfriend within the broader series, their relationship concludes when he chooses Tōko Amano over her, particularly following events tied to the "Romantie" book. After this rejection, Nanase continues to harbor feelings for Konoha but transitions into a supportive friend role. Her emotional journey includes periods of avoidance and attempts to inflict emotional pain upon him, depicted in the "Minarai" series. She explicitly tells Hinosaka of her desire to shield others from Konoha’s perceived emotional complexities, revealing protective instincts and unresolved attachment.

A significant aspect involves reconciling Konoha’s identity as a writer. She associates his novel-writing with a personality transformation she finds unsettling, preferring his version detached from literary pursuits. She directly reassures him that stopping writing is acceptable to her and that she would remain regardless. This stance underscores her desire for emotional stability and authenticity. After confessing these feelings to Hinosaka and processing events related to the second book (excluding the "Shoushin" incident), she achieves emotional catharsis, enabling her to continue loving Konoha from acceptance rather than resentment.