Soo Ji, a new student at Baekyeon Girls' High School, encounters the Pyramid Game where students rank each other based on popularity. Stuck at the bottom, she strategizes to improve her standing.
Soo Ji investigates her classmates' traits and the Pyramid Game's mastermind. She allies with vulnerable girls but her teacher is unhelpful. As the 14th game starts, truant Ja Eun returns.
Soo Ji grows anxious as events unfold, fearing her plan's exposure and Ha Rin's suspicions. Pyo Ji Ae worries about potential consequences of her actions. Soo Ji coerces Hae Jun into assisting, hinting she has leverage.
During parents' school visit, Soo Ji falls into Ha Rin's trap. She tries making a pact with Do Ah while Seung Yi acts to discredit her. Ha Rin manipulates the situation with her grandmother's help. Soo Ji resorts to Plan B.
During a school retreat, Ha Rin is pushed into the water while practicing diving. Ja Yeon rescues her. The next day, Class Five engages in a survival game with paint guns, and the last five students face the risk of being placed in Grade F
