Baekyeon Girls’ High School goes on a school retreat. While practicing diving, someone pushes Ha Rin into the water, and Ja Yeon jumps in to save her. The next day, Class Five plays a survival game using paint guns. The last five standing, Soo Ji, Ja Eun, Jae Hyung, Eun Jung, and Ji Ae are put in danger of ending up in Grade F.

Soo Ji decides to recruit more girls to end the game and Ha Rin for good. When Da Yeon is about to be punished for what she did to Eun Jung, their teacher tells everyone that Da Yeon has to transfer to another school. Meanwhile, right before the Pyramid Game is held, Ye Lim gets taken to the hospital.

The 16th Pyramid Game begins, and Ha Rin suggests choosing a classmate who will become a permanent Grade F. Before the voting takes place, Soo Ji tells the class that Ye Lim was attacked and hospitalized. The class decides to vote on whether to stay. playing or not, and the entire process is broadcast live, causing the school to be in an uproar. Meanwhile, Ja Eun tells Soo Ji what she did to Ha Rin when they were little.

Ja Eun reveals what she used to do to Ha Rin, but Soo Ji thinks Ha Rin is just using it as an excuse to make Ja Eun's life miserable. The school and Baekyeon Group decide to blame Soo Ji and her group for the violence at school, but Ms. Yoon Na Hee takes action and reveals the video of Soo Ji being bullied. Meanwhile, Soo Ji reveals the corruption behind the teacher recruitment.