Saya Takamine is a math teacher and homeroom instructor with cyan hair styled long with side-parted bangs and sidehair, violet or red eyes, a 157 cm slim frame, and measurements of 83-56-85 cm (C cup). Born into prestige, her elite education enabled skipping two school years and studying abroad, making her the youngest qualified teacher among peers. Her arrogant, rude demeanor targets underperforming students through the 'Student Quality Control Committee,' openly scorning the protagonist and earning widespread dislike.

She advises the Rhythmic Gymnastics club, demonstrating proficiency and owning gymnastic ribbons. Her wardrobe includes leotards, miniskirts, ballerina shoes, formal skirt suits, torn clothing, and slave collars under coercion. Unconventional behaviors involve dog cosplay, paw gloves, and pet collars. Dominant yet childish due to her sheltered upbringing, she remains sexually inexperienced, having never masturbated. She is Takamine Miyu's older sister.

Across official media, the protagonist blackmails and humiliates her, exploiting vulnerabilities through forced degradation, dog cosplay, and explicit sexual coercion. These acts challenge her elite self-image, with one narrative arc depicting her being "shown what a woman's real use is," stripping away her arrogance. Her psychological downfall remains fragmented across adaptations.