Ogasawara Sai is a 24-year-old Japanese language teacher at Atagi Private Academy, a young and dedicated educator beloved by her students for her cheerful and caring personality. However, her senior colleague, Mitsumura Yoshihiro, another Japanese language instructor, begins plotting to dominate and humiliate her after being publicly embarrassed by Sai in front of students. What starts as a classroom rivalry quickly escalates beyond mere workplace tension, spiraling into a dark and twisted conflict fueled by obsession, power, and revenge.