Cheongdam International High School

Kim Hye-in comes from a poor family. She's trying to change her circumstances to avoid spending her entire life barely making ends meet. One day, Hye-in witnesses the murder of a high school student. The victim turns out to be a classmate of hers who was bullied for her poor background. The murder is committed by a group of wealthy and influential students from the elite Cheongdam High School, led by Park Young-jin.
In exchange for her silence, Hye-in is offered a place at the prestigious Cheongdam School and financial support for her family. Desperate for help, she accepts.

Baek Jae Na is the class queen and queen of the Diamond 6 club, the most influential girl in school. She hates those who enter the school through the equal opportunity system.

Cha Jin Wook, the illegitimate son of the chairman of Chasel Medical, transfers to Cheongdam International School as the heir apparent. With his striking appearance, intelligence, and engagement to Jae Na, he reaches the top tier of Diamond 6. He proposes a contract marriage to Jae Na to consolidate his power. Although outwardly arrogant, he is a complex individual who saves Jae Na in a crisis and gives Yul Hee a chance. He develops secret strategies to prove his worth.

Min Yool-hee - After the truth about Hae-in and Woo-jin's relationship is revealed at the engagement party, Yool-hee's world crumbles. Enraged, Yool-hee turns away from her friend and begins searching for Jae-na's weaknesses in every way, even seducing her fiancé, Jin-wook.

Lee Sa Rang, the second son of the So Myung family, naturally entered Diamond 6 after entering Cheongdam International as a freshman. He fell in love at first sight with Hye In, who made a strong impression on him on his first day.

Seo Hee-kwon, Seo Do-yeon's uncle, is the new chairman of Cheongdam International. He comes from the Cheongdam Foundation's legal department.

Kim Hye-in (Lee Eun-sam) is a girl who grew up poor. She attends a regular school and struggles to make ends meet. She's constantly short of money, but she's ambitious and determined to improve her situation. One day, she accidentally becomes the only witness to the murder of a high school student. In exchange for her silence in the investigation, she's offered the opportunity to attend the prestigious Cheongdam International High School. Despite her guilty conscience, she accepts, as this is a unique opportunity that will help her change the status quo.

Kim Hye-In likes to take responsibility and make the first move, likes to quickly solve complex problems, is self-confident, behaves simply and straightforwardly, and takes pride in herself.

Baek Jae Na always hides her true feelings. She is cold towards people and keeps her distance from others. She doesn't like to talk much. She is rich and enjoys the luxury and comfort that come with a wealthy lifestyle. She likes to solve complex problems quickly. She approaches everything with a strict and unyielding approach to negotiations. She adheres to traditional approaches and dislikes unconventional ideas. She maintains a goal-oriented and serious attitude. She is self-confident and proud of herself.

Cha Jin Wook - , becomes possessive and gets angry when he feels that Jae Yi is liked by others or when others get close to her., likes to be in control of the situation., likes to playfully tease., cold towards people.