Miyahara-sensei is the first-year homeroom and physical education teacher for Reina Aharen and her classmates. She possesses an adult-like appearance with long, dark brown hair reaching chest length and brown eyes. Her typical attire includes a white dress shirt, green skirt, dark beige stockings, black shoes, and a green brooch.

She radiates warmth, gentleness, and helpfulness, fostering a friendly atmosphere that builds trust among students and colleagues. Miyahira-sensei cares deeply, especially for her close friend Ms. Tōbaru. Outside school, she affectionately calls her "Momo-chan," while maintaining formal address during work hours. Their friendship involves frequent shared meals, outings, and trips. Miyahira actively supports Tōbaru during illness by visiting her home and preparing homemade meals.

Beyond teaching, she provides practical help to students, such as lending her personal car to Shōta Raidō and his friends for camping. A lesser-known but substantial trait is her surprisingly large appetite, capable of consuming impressive quantities of food. As homeroom teacher, she consistently prioritizes her students' well-being.