Girl #21 Yoshimi Yahagi is a rebellious girl with wavy, long hair and is in a relationship with Yoji Kuramoto (they met while watching a movie).
Yoshimi Yahagi is one of the class of third-year students at the fictional Shiroiwa Junior High School. She was a member of the gang headed by Mitsuko Souma, along with Hirono Shimizu. Yoshimi used to regularly steal from and torment her classmates. She often singled out Kaori Minami out of the girls. Yoshimi is described in the novel as one of the more urban girls in Shiroiwa; she never saw a sickle before in her life.
Yoshimi was in love with Yoji Kuramoto, her boyfriend. They met at school and started dating when they ran into each other while out shopping. They first slept together on Saturday 18th January. She was arrested several times for theft, and once for blackmail. She dabbled in prostitution, after Mitsuko Souma introduced her to some middle-aged men who were willing to part with their money, but she stopped when she started dating Yoji.
In the manga, Mitsuko had allowed Yoshimi to be raped by two men, charging them extra because she was a virgin. With the money she gained, decided to see a movie based on her favorite TV show, Alley Cats. During a tragic scene, she noticed Yoji was sitting next to her, crying. The two recognize each other from class. He tells her that he is a big fan of the actress who plays the main character of the movie. Afterwards, Yoji admits that the reason he likes the actress so much is because she looks like Yoshimi. From then on, the two started dating.