Seki-sensei teaches as a homeroom instructor across multiple grade levels. She possesses tan skin and dark purple eyes matching her hime-cut hair, consistently accenting her appearance with dark red lipstick. Her professional wardrobe features a black shirt under a purple blazer, paired with a purple pencil skirt and black high heels.

Her demeanor merges strictness with compassionate undertones. She enforces clear behavioral standards, exhibiting impatience toward rule-breakers by sometimes hurling chalk at distracted students. Beneath this stern exterior, she actively monitors student welfare, providing emotional support during personal struggles. Her blunt honesty initially intimidates but ultimately reveals an approachable nature.

Her background includes attending the elite Karen Girls' Academy in middle school, where she gained notoriety for confronting bullying boys. Her childhood father's death complicated her teaching career, as certain private schools questioned her suitability due to her single-parent upbringing. This history shapes her educational approach, blending firm discipline with empathy for overlooked student hardships.

Personal evolution emerges through a romantic subplot where colleagues and students learn of her relationship with Kitagawa. When he receives a job transfer invitation to New York, she declines accompanying him to prioritize her current students' graduation ceremony. They sustain long-distance communication with reunion plans post-academic year.

Beyond classroom duties, her dynamic with colleague Yuki-sensei strains when Seki conceals her relationship, echoing past friction over Yuki's undisclosed dating life. Her student interactions evolve across years: initially instructing Doremi Harukaze's entire class, later teaching only Doremi, and eventually Pop Harukaze per light novel canon.

Notable trivia includes her motorcycle-riding skill and the theory linking her name to Hiromi Seki, a Toei Animation producer associated with the series.