Masuyo Ikari is the homeroom teacher for the Kimengumi class in middle school, later transitioning to teach the Kojougumi class in high school, specializing in speech education.

Students nickname her "Ikari Kong" due to her easily triggered, hysterical personality and fiery temper, often exclaiming "Ikari masu yo!" when angered. Despite this volatility, she presents a professional and beautiful image as an educator.

Her connection to the Kimengumi students runs deep, as she was once their older senpai at the same school they all attended. This shared history fosters a unique familiarity within their dynamic.

Her personal story progresses significantly when she marries fellow teacher Takuma Sessa. Their relationship culminates in marriage, and they later welcome a son named Tenma, marking her journey into motherhood alongside her teaching career.