Nadeshiko Sōma is a supporting character who serves as Shinichirō Asano's homeroom teacher and the school nurse at the same institution where Shinichirō and Sakuya Shimazu study. She is also the older sister of Matsuri Sōma and an appointed guardian of Sakuya from the Shimazu clan. Nadeshiko has neck-length black hair, brown eyes, and typically wears glasses along with a lab coat, reflecting her dual role as an educator and medical professional.

Her personality is playful and mischievous; she frequently teases both Shinichirō and Sakuya, often engaging in lighthearted pranks or remarks. Despite her professional position, she maintains a relaxed and somewhat flirtatious demeanor, even going so far as to jokingly propose marriage to Shinichirō as a way for him to avoid job hunting. This behavior underscores her underlying interest in him and her tendency to use humor to navigate serious situations.

Nadeshiko's primary motivation appears to be a genuine care for those under her supervision—both as a teacher and as a clan-appointed guardian. She takes an active role in connecting Shinichirō to the Shimazu family, initially recommending him for a part‑time job that leads him into the world of demon hunting. Her connection to the supernatural side of the story is further evidenced by her technical or magical skills: she is responsible for creating an artificial body that allows another character (Suseri Shimazu) to maintain a youthful appearance indefinitely, demonstrating a notable ability in crafting or alchemy.

Within the story, Nadeshiko functions as a reliable adult figure who provides guidance, medical support, and occasional comic relief. Her relationship with Sakuya is protective, while her dynamic with Shinichirō mixes professional authority with personal teasing. She does not undergo significant character development over the course of the series, remaining a steady presence who facilitates the main cast's activities.