Kim Hyoyeon She is a hardworking, tough girl who always think she is weak. She is outgoing, normal high school girl. She often seems immature and irritating, she is a kindhearted, innocent, honest person, She is offered a scholarship to attend the prestigious school as She attends the same school with the F4. She first like minho as she though he was kind, as She gradually falls in love with him in the early chapter. As she sooner found out that it was all about the game. Minho left for the states, knowing that hyoyeon doesn't love him anymore as she later follow minho on. She was expecting that minho will accept her again, but she was suddenly send her away. She doesn''t lose hope and she stay and work in the states as she sooner realised that she is falling in love to Seunghoon kindness. Later on, Minho was back to love her again.  

Song Minho A handsome, rich and snobbish guy and the leader of his group named f4. The younger son of the owner of Yg Group, the most powerful business groups in South Korea. He thinks money can solve anything. He is at first is angry at Kim Hyoyeon for not following his rules in school. And after the day,  His friends wanted him to court her and ask her to be his girl friend in one hundred day and take his ity and will tell her that he doesn't love her and all that happened between them was a game. But he ends of falling inlove with her. But the stubborn and snobbish young man becomes apparent that he is in fact lonely, sensitive, yet warm and kind.

Lee Seung Hoon He is a soft-spoken and kind and insensitive young man. He is the person whose Minho can lean on. After getting rejected by his girlfriend Jessica, when he proposes to her. He decides not to fall in love at any girls or enter in a new relationship. He later met Hyoyeon, At first, he is irritated by her naive and being clumsy but he begins to open his heart to her and fall in love as he recognises how genuinely sweet she is. His friendship with Minho almost ends over Hyoyeon. Later on, He becomes Hyoyeon's savior.

Kim Han Bi aka B.I He is a fun-loving playboy and the youngest on there group. that only date girls no longer than a week and close to Seung hoon && Jinwoo. He is nice to Hyoyeon and he rather become protective of her. his family owns the country's biggest museum in paris. He eventually change his playboy style when he realizes that he is in love with Taeyeon (Hyoyeon's bestfriend).

Kim Jinwoo He is the other playboy, He is the serious type with a moody personality. His family owns the biggest hospital in korea. At the young age, Jinwoo already begun as the official doctor on there own hospital. They often called him, Dr. Kim. He is also in love with Taeyeon, His childhood crush as his play boy ways changes when he found out that taeyeon as romantic feelings towards B.I as He is willing to stay her friend only. And he after met, Yuri. Hyoyeon's another best friend. He does not develop romantic feelings for Yuri as he eventually become very sweet and taking care of her and becomes good friends and later found out that he falls inlove to yuri. 

Kim Taeyeon. Hyoyeon's Bestfriend,  She falls for B.I after he helps her to pretend to be his boyfriend in 1day.

Kwon Yuri. She is Hyoyeon's 2nd best friend, She is the crazy patient of Jinwoo. When she almost killed herself because of her ex-boyfriend cheats on and left her. She was love at first sight with Jinwoo's charm.