The absolute pinnacle and reigning 'Queen' of the school's top power circle, 'DIAMOND6'. As the only daughter and likely successor of the Hanmyung Group, Korea's top conglomerate, she is a minor with the highest individual assets in the country (estimated at over 1 trillion KRW). She commands the school using money and rank as weapons, drawing attention like a celebrity with her perfect appearance and background, but she hides deep emotional scars and a sense of deprivation regarding her family life. She is engaged to Cha Jinwook.

In Season 1, she was portrayed as a member of 'DIAMOND6' and a chaebol daughter dreaming of a peaceful marriage. However, in Season 2, she has turned into a cruel figure driven solely by revenge after being betrayed by her most trusted friend and lover.

A scion of a chaebol family ranked within the top 30 in the business world. On the surface, he appears to live a perfect life as the official partner of Min Yulhee, to whom he was betrothed by their families, but he is the core troublemaker who triggered the entire series of events.

The 'King' of the school's top power circle, 'DIAMOND6', and the son of the Chairman of Cheongdam International High School (heir to the Cheongje Foundation). Although he is a top-tier power holder, unlike other entitled students, he is a character who hides deep wounds and complex emotions behind a cynical exterior. He works to uncover the truth behind the 'Kim Haein Fall Incident'.

She has fully awakened from being a 'dirt-spoon witness who was trampled upon' to a 'new member of DIAMOND6 who shakes the foundations of the establishment'. While she desperately endured Baek Jena's violence in Season 1, in Season 2, she takes an independent and aggressive stance, seizing the power of the upper class to face the true culprits who threaten her head-on.

A fatal and dangerous transfer student who appears cold and calculating on the outside but leads a massive revenge plot from within. Cha Jinwook reaches the top of the school by partnering with Baek Jena on the surface, but behind the scenes, he leads a double life as 'Black Dog', the architect planning the destruction of the school and the foundation, driving the plot's biggest twists. He is engaged to Baek Jena.

A straightforward younger student who follows his crush at first sight, and the youngest member of DIAMOND6 who hides a secret. Amidst the cutthroat power struggles, Lee Sarang acts as Kim Hyein's reliable black knight, embodying the classic devoted younger man while serving as a key 'cheat key' for the ending.