Rio Kitagawa is a tall, academically gifted high school student distinguished by her striking looks and understated awareness of her own attractiveness, a trait that stirs envy in classmate Akane Kobayashi. She balances playful charm with tenacious determination, regularly teasing Mika Suzuki—a petite, youthful-looking 27-year-old teacher whose innocent demeanor captivates Rio. Their exchanges revolve around Rio’s flirtatious, occasionally overbearing advances, which blur the line between affection and harassment.

Openly lesbian, Rio fixates on individuals with petite frames, especially Mika. Her infatuation fuels calculated decisions, such as failing exams to engineer private tutoring sessions, blending manipulation with genuine pursuit. A subtle sadistic tendency surfaces in acts like coaxing Mika into overindulging on chocolates to elicit discomfort or crafting hypothetical contests celebrating Mika’s unique traits.

Though academically capable, Rio often sidelines school obligations to prioritize her obsession. Her teasing lightly targets Mika’s insecurities about weight, framed as cheeky camaraderie rather than cruelty. Her given name combines Japanese characters for “white jasmine/village” (莉/里) and “center/cherry blossom” (央), contrasting with her surname Kitagawa (“north river”).