Yayoi Sanzenin presides as the school nurse at Koyomi Academy, her life steeped in dual legacies as both healer and the 13th-generation miko of the Tonami-style Sanzenin Shrine. Born into a lineage devoted to Shinto traditions, she supports her parents at their family temple while balancing duties at the academy. Early spiritual training sharpened her intuition, enabling her to detect unseen threats and mobilize swiftly to shield those under her care.

At school, she navigates corridors in a crisp white nurse’s coat and tailored skirt, contrasting her home attire of flowing priestess robes that mirror her sacred heritage. Though typically composed, she shifts seamlessly into stern authority when provoked, brandishing a katana to command obedience—particularly during clashes with Chitose Hitotose. This duality reflects her intertwined identities: gentle caregiver and unyielding guardian.

Dubbed the "Hospital Hottie," her allure draws male students to feign ailments for her attention, yet her expertise extends beyond nursing. A kendo practitioner and precise swordswoman, she intercedes in conflicts, especially when Chitose’s safety is jeopardized. Her medical degree from Minato Girls’ University underscores her dual qualifications, merging clinical skill with spiritual vigilance.

Within her household, spiritual acuity heightens her nurturing instincts, driving her to mentor Chitose toward maturity. While their bond evolves subtly across adaptations, her focus remains steadfast on his growth, never straying into overt romance. Across media—series, OVAs, games—she upholds a seamless equilibrium between miko rituals and modern pedagogy, her portrayal unwavering in its consistency.