Girl #20 Kaori Minami is a student with acne who idolizes pop star Junya Kenzaki. She is friends with Megumi and Mizuho, though she finds Mizuho's fantasy games irritating.
On the island, Kaori loses her sanity after killing a cat and gets into a gunfight with Hirono. Despite wounding Hirono, Kaori is shot in the head. She is part of the third-year class at Shiroiwa Junior High School, a fictional institution located in Shiroiwa town, which is situated in Kagawa Prefecture in the novel and manga, but in Kanagawa Prefecture in the film.
Kaori was an avid fan of Junya Kenzaki from the group Flip Side. She wore a locket containing his picture under her uniform, a unique item available only to members of the Flip Side fan club. Her favorite song is "Galaxy Magnum" by Flip Side.
In flashbacks within the manga, she is frequently bullied by Mitsuko's gang, who steal her money. Other students mockingly call her "pizza face," leading to her mental breakdown during the program, often repeating, "No more pizza face!"
After leaving school, Kaori was the last girl Yukie Utsumi tried to recruit into her group. However, seeing that Yukie was with five other girls made Kaori too paranoid to trust her, and she chose to run away instead.
In the novel, just before noon, Kaori, sitting alone and thinking about Junya Kenzaki, encounters Hiroki Sugimura. Startled, she shoots at him, and he disappears. This encounter causes her thoughts to spiral downward.
In both the novel and manga, Kaori accidentally runs into Hirono Shimizu, resulting in a gunfight. Kaori wounds Hirono in the arm. Shuuya Nanahara witnesses the fight and tries to intervene.
In the novel, while Kaori is distracted by Shuuya, Hirono shoots her in the shoulder and then in the head, causing a portion of her skull to explode. She dies as a result of the headshot.
In the manga, Kaori becomes mentally unstable after accidentally killing a cat. Later, she engages in a gunfight with Hirono. Shuuya steps in, promising help and safety, creating a temporary ceasefire. He persuades Hirono to join him. However, Kaori, driven mad, attempts to shoot them both, but is killed by Shougo Kawada, who shoots her multiple times in the head with a shotgun.
Shougo tells Shuuya that he regrets having to kill Kaori but felt it necessary as she had become insane, evident from the look in her eyes.
