(Lee Min-ho) as Kim Tan
The heir of the Empire Group. He is arrogant and self-centered however he is overshadowed by his older half-brother, Kim Won. He falls in love with Cha Eun-sang despite her poor background.
(Park Shin-hye) as Cha Eun-sang
Daughter of the Empire Group's housekeeper. She grew up with Yoon Chan-young and gets caught in a love triangle with two privileged men, Kim Tan and (Choi Young-do.)
Kim Woo-bin as Choi Young-do
The heir to a luxury resort. He has an IQ of 150, but uses his wit to put down and harass his friends rather than to excel in his studies.
Kang Min-hyuk as Yoon Chan-young
Son of the Empire Group's secretary. Cha Eun-sang's best friend who falls in love with Kim Tan's ex-girlfriend, Lee Bo-na.
Krystal Jung as Lee Bo-na
She lives a fabulous lifestyle as the daughter of an entertainment executive. Her first love and ex-boyfriend, Kim Tan never loved her. Yoon Chan-young heals her heartbreak.
Kim Ji-won as Rachel Ryu
Kim Tan's fiancée. A haughty and chic heiress of a major hotel group, she is a girl who wants for nothing in the world.
Kang Ha-neul as Lee Hyo-shin
Son of the Chief of Police. He is the student body president, and has a crush on his teacher, Jeon Hyun-joo.
Park Hyung-sik as Jo Myung-soo
Son of the CEO of a car import company. Quick to think on his feet, he's a slacker who doesn't want to inherit the family business.
Choi Jin-hyuk as Kim Won
Kim Tan's "perfect" older half-brother, an accomplished and capable young executive who runs his family's giant conglomerate, Empire Group.
Im Joo-eun as Jeon Hyun-joo
A teacher at Empire High School, she looks cool and collected on the outside, while being slightly awkward in real life. Hyun-joo gets Kim Won's attention for her sharp intelligence, although studying is the only thing she knows how to do.
Kim Sung-ryung as Han Ki-ae
Mother of Kim Tan.
Yoon Son-ha as Esther Lee
President of Chrystal Hotel. Mother of Rachel Ryu, and remarried to Choi Dong-wook.
Choi Won-young as Yoon Jae-ho
Empire Group secretary. Father of Yoon Chan-young, and previously involved with Esther Lee.
Choi Jin-ho as Choi Dong-wook
President of a luxury resort. Father of Choi Young-do, and remarried to Esther Lee.