Koyomi Mizuhara, commonly known as Yomi, is a grade-school friend and general antithesis of Tomo. She is the voice of reason of the series, carrying herself as the most mature and sometimes bitter member of the group. Though smart and athletic, she is constantly dissatisfied with herself due to her weight and is always trying various diets in an effort to become thinner. While usually functioning as Tomo's "straight man", she sometimes manifests a rather cruel sense of humor, such as tricking the cat-tongued Osaka into eating an extremely spicy croquette. Compared to most of her peers, Yomi uses more masculine Japanese speech patterns, especially when dealing with Tomo's antics.