Kim Hye-in is a high school student from a poor background. She becomes the only witness to the murder of a high school girl. In exchange for her silence on the murder she witnessed, she is offered a chance to study at Cheongdam International High School, the most prestigious high school. There, Kim Hye-in meets Baek Je-na, the leading suspect of the murder and the most powerful student at Cheongdam High. They engage in psychological warfare full of tension and a fierce power struggle.

After the fall of villain Oh Shi Eun in Season 1... The once unshakable hierarchy at Cheongdam International High School is now fractured! Kim Hye In, the witness of two murders the first member of Diamond 6 from an underprivileged class. Baek Je Na, the Queen whose world is endangered after the crumbling of the succession structure, strained friendship, and suspects toward her as the murderer. Kim Hae In, the Cinderella who returns dreaming of revenge but not love. Seo Do Eon, who is in confusion after facing the tragic truth of what he has believed as love. Min Yul Hee who chooses to embrace thorough unhappiness if happiness is unattainable. Park Woo-jin, full of selfishness and inferiority complex. And Lee So Mang, an unexpected mastermind. And now, a powerful new face enters the scene, shaking everything up! Once again, Hye In and Je Na find themselves at the center of it all. Will they make the same choice, or will they choose differently?