The story starts with robbers hijacking a plane at a Japanese airport. Yankumi, a woman from a powerful Yakuza family, bravely defeats the hijackers, making headlines. She is a math teacher at Aado High School, keeping her background secret. Yankumi is advised to stay out of the spotlight by the principal. A former student, Odiri, becomes an apprentice teacher, but Yankumi's students disrespect her. Yankumi tries to introduce Odiri to the students, but they ignore her. Meanwhile, a group of students on the roof discuss Odiri's return. Yankumi's former students are surprised to see her with Odiri.