Mako Mizukoshi attends Kazami affiliated school as a junior high student in class 3-1. Her affluent background stems from her father's role as director of the local hospital, and she has an older sister named Moe alongside a younger brother. Physically, she sports short blue hair with spiky bangs and green eyes, standing 154 cm tall with a 40 kg weight. Her slim figure measures 80-55-85 cm. Her personality features a short temper and frequent grumbling, particularly when provoked by Jun'ichi Asakura or her rival Suginami. Despite this irritable exterior, she secretly holds feelings for Jun'ichi, displaying modern tsundere traits by masking concern with outward frustration. She maintains a close friendship with Nemu Asakura, often showing genuine worry for Nemu's well-being. Her rivalry with Suginami, rooted in elementary school, consistently sparks quarrels and teasing exchanges. During lunch breaks, she habitually joins her sister Moe on the school rooftop to share nabemono meals. As an active music club member, she plays the soprano flute.