Sakie Satō balances her career as a mathematics teacher with her existence as a succubus, a condition demanding significant lifestyle adjustments. She possesses fair skin, long black hair typically secured in a ponytail, and wears glasses intentionally to reduce her allure; concealing clothing, such as a red tracksuit, helps minimize her noticeable figure and prevent accidental exposure of her features, which amplifies her effect on others. Without these precautions, her natural beauty and physique become more pronounced, intensifying her succubus traits.

Her succubus physiology involuntarily releases potent aphrodisiac pheromones affecting nearby individuals, particularly straight men and gay women, often unleashing hidden aspects of their sexuality. This results in extreme self-consciousness, social anxiety, and a timid, reserved personality. She maintains strict distance from males, experiences profound loneliness, and lives remotely to minimize neighbor contact. Her daily routine involves waking at 4:15 AM and commuting during the first and last train services to avoid crowds. Initially, she believed her pheromones had no effect on biology teacher Tetsuo Takahashi due to his composed demeanor, fostering her admiration and eventual romantic feelings. Later revelations showed Takahashi was affected but masked his reactions to respect her comfort, deepening her emotional connection.

Key relationships form her support system. Police officer Ugaki has acted as a father figure since she was 14, providing guidance after her own father struggled with her condition; he remains one of the few men she trusts, adhering to distance protocols. Among colleagues and students, she bonds with Yuki Kusakabe over shared manga interests and demonstrates consistent care for all her demi-human students. Her romantic progression with Takahashi evolves from friendship to dating by chapter 80 of the manga, though physical intimacy presents challenges—a simple hug strains his self-control due to her pheromones. The narrative concludes with them navigating a relationship after losing her virginity, confirming her succubus nature persists post-virginity, countering earlier implications about its connection.

Her background includes estranged parents, with her mother mentioned as a probable cohabitant earlier in life. Professionally, she rejects government financial aid available for succubi of her potency, preferring normalization through teaching. Her character development centers on gradual self-acceptance: initially overwhelmed by her traits, she slowly engages more openly with others, particularly through her relationship with Takahashi, despite ongoing challenges managing her physiological effects on him and society.