Natsume Nakashima, a former colleague and classmate of Lilith from their boarding school days, arrives at Yuuri's mansion determined to persuade Lilith to return to their previous employer, Yagami. Lilith had left that position abruptly without notice. After Natsume's written demand for her return was refused, she intervened personally. Natsume struggles to understand why Lilith works without salary for Yuuri, a child, instead of accepting stable employment under Yagami—whom Natsume considers a reliable adult offering better pay and a more prestigious household environment.

She possesses light orange hair styled in twin tails reaching her chest, distinctive sharp teeth, and light yellow or olive eyes. Her attire consistently features a traditional black maid dress with a white apron, a white mob cap, dark brown boots, and short black gloves.

Natsume persists in her missions but exhibits contradictions in emotional expression. She openly worries for Lilith's well-being and professional reputation while concealing her own romantic feelings for Lilith, initially deflecting or denying them when confronted. She later openly admits these feelings, acknowledging her intense focus on Lilith stems from genuine concern and affection. Concurrently, Natsume nurses unrequited romantic feelings for her master, Yagami. She struggles to articulate why she loves him, citing his flaws—laziness, emotional volatility, and a penchant for sweets—alongside his consistent presence despite treating her like a child.

Her competencies as a maid are lacking; Lilith frequently assisted her during their service to Yagami due to Natsume's deficiencies in household duties. She possesses poor financial management skills, spending impulsively on shopping and leaving no savings, contrasting Yuuri's frugality. Academically, she lacks depth, exemplified when she tests Yuuri on the theory of relativity—a concept she cannot grasp herself.

Natsume's character develops from stubborn insistence on retrieving Lilith to recognizing Yuuri's suitability as Lilith's employer. She observes his thoughtfulness, care for Lilith, and responsible financial habits, eventually conceding Lilith's choice may be valid. Visiting Yagami's estate, she assists Yuuri's aspiration to become a "dandy" like Yagami, advising him true maturity involves actions beyond words—even while criticizing Yagami's unsuitability as a role model. She experiences personal growth in emotional honesty, moving from suppressing feelings to admitting her love for Lilith and acknowledging the complexity of her emotions toward Yagami despite their challenging master-servant dynamic.