Miyuki Koizumi is a central character in the anime Dokkiri Doctor, serving as the school nurse at the clinic and health center managed by the doctor, Haruka Nishikikōji. She is introduced as a childhood friend of Haruka, a bond that forms the foundation of their relationship throughout the series. Miyuki is described as a pretty and capable nurse, but her role extends far beyond typical medical duties. She frequently acts as the voice of reason in the face of Haruka's eccentric and often malfunctioning inventions, helping to fix the chaos those creations cause. Her personality is grounded and practical, making her the series' primary straight man, or tsukkomi, who reacts with exasperation to the absurd situations that unfold around her. Despite this, she is not simply stern; she shows genuine care for Haruka and the students, balancing her sharp tongue with kindness and compassion. Miyuki possesses notable physical abilities, being highly skilled in martial arts, particularly karate, and has won numerous competitions—a contrast to her gentle appearance. Her motivations stem from a sense of responsibility and loyalty: she wants to protect the school community and support Haruka, even though his antics often frustrate her. Their relationship is complicated by unspoken romantic feelings; Haruka constantly tries to impress her with his inventions, but his shyness and the resulting disasters keep them in a platonic, almost fiancé-like dynamic. Over the course of the story, Miyuki remains a steady, common-sense anchor, showing growth in her patience and willingness to handle the unpredictable consequences of Haruka's genius. Her most notable abilities include her martial arts prowess, her medical knowledge, and her talent for damage control when experiments go wrong.