When the students create posters making fun of her and the head teacher, Yamaguchi learns that they have given her a nickname, "Yankumi", which she unexpectedly embraces. One of the students, Minami, is seeing a new girl. One day, he arrives badly beaten and gets into a fight with another student, Sawada. It turns out that the girl Minami is seeing was also going out with a boy from another school, who calls him out on the matter. Inspired by her grandfather's yakuza values, Yamaguchi encourages the boys to stick up for their friend.
