Miss Ayumi is a teacher at Graviton High School, where she has the three protagonists A-ko, B-ko, and C-ko in her class at the same time. Her daily responsibilities include trying to get C-ko to pay attention to her lessons while also doing her best to prevent A-ko and B-ko from physically fighting each other. She is usually seen teaching poetry, and she often rides a moped to school. She becomes visibly agitated and scared whenever anything goes wrong in her classroom, such as C-ko’s incessant crying or B-ko’s remarks about the class being boring.

Beneath her outwardly nervous and somewhat frazzled demeanor, Miss Ayumi nurses a secret gloominess in her soul. Both of her parents are deceased, and she worries that she will never fall in love. This personal sadness drives her to take unusual steps in her search for a husband. At one point she prays over a hexagram‑marked pendant, a detail that later coincidentally resembles certain alien clues. Ultimately, Mr. Daitokuji arranges a match for her with a man named Kei, and she accepts the arranged marriage. The wedding nearly takes place, but is canceled at the last minute due to a series of interconnected and chaotic events.

Miss Ayumi is also a member of the Volunteer Defense Force, a loose organization of citizens who step in to defend the city when the official authorities fail. In the film Cinderella Rhapsody, when a brawl between A-ko and B-ko escalates into a citywide alert, Miss Ayumi immediately dons a flamboyant superhero costume and rides a gravity‑defying cycle into action. Her outfit’s skimpy design was a holdover from the time when Project A‑ko was originally planned as an adult series.

She loves fireworks displays and is an avid swimmer. Her subject appears to be literature. She is a supporting character throughout the series, appearing in Project A‑ko as well as its sequels.