Mifuyu Kiba, a second-year student at Takafuji Private Academy, entered school a year later than her peers following surgery, an experience that initially fostered feelings of inferiority and discomfort. Born in Hokkaido, her name reflects this wintry origin: "美" (mi) meaning "beautiful" and "冬" (fuyu) meaning "winter."

Though kind-spirited, she presented a reserved and withdrawn demeanor, often seen reading or wearing headphones, creating a cool and unapproachable impression. Despite this, she possesses notable intelligence, particularly in economics and finance. She quickly formed close friendships with Yūki Ōjima and Chisato Sumiyoshi after transferring, establishing a daily routine of walking to school together.

Serving as treasurer of the Food Research Club, Mifuyu's economic expertise and natural leadership became vital assets during Yūki's campaign for student council president. Her role evolved from background member to key strategist as she leveraged her financial acumen to support the club's survival.

Secretly, Mifuyu harbors romantic feelings for Yūki Ōjima but actively suppresses them to avoid jeopardizing her friendship with Chisato, whom she knows also cares for Yūki. Prioritizing Chisato's happiness, she outwardly supports a potential relationship between Chisato and Yūki, demonstrating selflessness and loyalty. Her compassionate nature further emerged when she guided Chisato to confront and overcome depression following Yūki's traffic accident, helping Chisato accept her own feelings for Yūki.

Socially, Mifuyu participates in comic skits and gags with Yūki and Chisato in public, sometimes drawing attention. She is fiercely devoted to her friends, consistently going out of her way to provide support and guidance, especially to Yūki during the election challenges. Physically, she has ochre hair, lilac eyes, and stands 1.66 meters tall. A recurring character element is her declaration, "I'll never betray chocolate," emphasizing her alignment with the Food Research Club's interests.