Main Characters:

Choi Sulli as Bae Mi Yoon

An intelligent working student from the first year of college, she works as a delivery girl in a fast food chain, her dream is to  study in Kirin Arts School however they are poor and cannot afford to make her to study there, luckily there is an open audition in Kirin and with luck and talent she passes, she became friends with Yoo Young and Ha Na and became acquianted with the Choi cousins.

Personality: Bubbly-Friendly-Sweet

Kang Min Hyuk as Choi Yoon Seuk

A rich boy with no dreams, he is home-schooled and haven't been in a regular school before, his grandmother threatens him to go to Kirin to have goals in his life or he will lose all his heir money, by that he goes to Kirin and mets Mi Yoon, he used to hate her but then he was amazed by her beauty and hardwork as the series continues he falls for Mi Yoon.

Personality: Arrogant-Cold-Selfish (As the series continues he became a sweet-sensitive-cheerful boy) 

Kevin Woo as Choi Min Woo

An intelligent and cheerful boy, his cousins are Yoon Seuk and Jae Myun, unlike his cousin Yoon Seuk he has shown interest in their comapny's business, he fell for Mi Yoon when he first see her perform live as the series continue he tries to get Mi Yoon's heart and becames Yoon Seuk's biggest rival.

Personality: Cheerful-Bubbly-Sensitive (As he becomes Yoon Seuk's rival in Mi Yoon he became Cold-Selfish when he's with Yoon Seuk) 

Ahn So Hee as Hong Yoo Young

A heartthrob in their school, she's very good in singing and dancing, she has a crush on Min Woo for a long time at first she was friends with Mi Yoon but when she knew that Min Woo like Mi Yoon she talk behind Mi Yoon's back.

Personality: Lovely-Friendly-Bubbly 

Yang Yoseob as Hong Joo Myun

He is the older brother of Yoo Young, he is very caring for her younger sister but his personality is very different from his sister, while her sister is busy in her social life, Joo Myun is there reading a book.

Personality: Quiet-Sensitive-Caring 

Park Gyuri as Yoon Ha Na

She is known as the older sister of the group, she's caring for her friends, she's also good at singing and dancing, to her friends she is single but unknown to them she has a boyfriend in the United States.

Personality: Caring-Sweet-Sensitive