Koyomi Mizuhara, also known by her nickname 'Yomi', is one of the main characters in the anime and manga series Azumanga Daioh. She is a responsible and level-headed student, often acting as the voice of reason among her more eccentric friends. Known for her glasses and slightly sarcastic demeanor, Yomi is academically driven and cares about her health, though she struggles with her weight. She plays an important role in the group as a stabilizing influence and close friend to Tomo Takino.