Miori Mitō is a major supporting character first introduced in the university arc of the series. She is a first-year student enrolled in the International Business program at Yokohama City University, the same institution attended by Sakuta Azusagawa, Mai Sakurajima, and Nodoka Toyohama. She appears in the story beginning with the tenth volume of the light novel series and becomes a central heroine in volumes fourteen and fifteen, which are adapted into the anime season Rascal Does Not Dream of Santa Claus.

Miori possesses a cheerful and approachable personality that helps her form friendships quickly, making her well-liked among her peers, particularly by male students. She has a laid-back and somewhat naive demeanor, but she also displays an unpredictable side that can surprise those around her. One of her most distinctive traits is that she does not own a smartphone, a choice that sets her apart from most of her generation and serves as an early point of connection with Sakuta, who shares a similar disinterest in mobile technology. She follows trends and dresses up, but she does so for her own satisfaction rather than to impress others.

Her role in the story is linked to the central mystery of the season, as she becomes a key figure in unraveling the Kirishima Touko phenomenon and helping to resolve a widespread outbreak of Adolescence Syndrome that affects many people. She is among the few individuals who can perceive certain supernatural occurrences, such as the invisible girl Nene, indicating that she herself may be affected by Adolescence Syndrome. Her bond with Sakuta develops through their shared aversion to smartphones and her willingness to involve herself in the strange events unfolding around them.

While specific details about her personal background, motivations, and character development are not extensively documented in the available sources, she is portrayed as a confident and self-assured young woman who is not easily swayed by others. She declares herself a potential friend openly and engages with the world on her own terms. Her relationships with other characters, especially Sakuta, are central to her involvement in the plot, and she contributes meaningfully to the resolution of the season's conflicts. No supernatural abilities of her own are described, but her sensitivity to the syndrome phenomena marks her as important to the story.