While delivering a student’s dry cleaning Geum Jan Di saves the life of a student at the most prestigious school in Korea. Her actions soon become public and exposes the bullying within the school. To silence the public’s attention Jan Di is offered a swimming scholarship to Shinhwa which she declines. Her family forces her to attend.During her first day at Shinhwa Jan Di learns of the famous F4 and of the other students adoration and fixation with the boys in the group. Gu Jun Pyo,Yoon Ji Hoo, So Yi Jung, and Song Woo Bin are the richest and most powerful kids within Shinhwa and Korea. Subsequently they use their power to terrorize weaker students or those they do not like. Jan Di, instead of being impressed becomes enraged and fantasizes about confronting Gu Jun Pyo, the leader and initiator of many of the bullying acts. She gains courage to confront him when a friend accidentally spills ice cream on his shoes and he demands the girl lick it off. Jan Di defends her friend and attempts to reason with Jun Pyo’s tyrannical demand. When he refuses to relent Jan Di turns violent, knocking Jun Pyo to the ground. Engaged by this Gu Jun Pyo declares war on Jan Di and encourages the other students to bully her. Jan Di however is resistant, refusing to apologize to Gu Jun Pyo, and stands by her decision to fight him.
Ironically, Gu Jun Pyo, having never been stood up to, begins to develop feelings for her. He tries unsuccessfully to woo her as she slowly begins to spend more time with Jun Pyo and his friends. Jan Di teaches Jun Pyo that money cannot buy everything and in order to have real friends he himself must be real or use his heart, but Gu Jun Pyo still does not understand why someone like Jan Di should dislike him. As the story progresses Jun Pyo falls deeper in love with Jan Di and she learns how to open herself to his love as well.
As love begins to blossom, Jun Pyo’s mother discovers them and deems it unsuitable. She does everything in her power to keep the two apart, even arranging a marriage for Jun Pyo. Other factors keep arising as another member of the group falls in love with Jan Di and in a twist of fate Jun Pyo loses his memory. In the end, however, Gu Jun Pyo and Jan Di learn that love conquers all and that they are truly soul mates.
Jun Pyo and Jan DiJan Di initially hates him and his two friends, So Yi Jung and Song Woo Bin. She is the only one who is strong enough to stand up against Jun Pyo after he attempts to humiliate Min Ji, Jan Di's only friend at the school. Jun Pyo then puts a red card in Jan Di's locker which indicated that she was a victim of the F4. After continuous bullying, his feelings for Jan Di begin to develop. However, Jan Di dislikes him for what he had done to her and she already has taken a liking in Ji Hoo. Jun Pyo persists in showing Jan Di his affections and after the event of going on a date with her, she realizes her feelings towards him. As their relationship becomes official, Jun Pyo's mother became an obstacle. She does everything possible to prevent Jun Pyo from being with Jan Di, as she believes that her son, Goo Jun Pyo shouldn't be dating a commoner (referring to Jan Di).
Ji Hoo and Jan Di In the beginning, Jan Di develops a crush on Ji Hoo. The first time Ji Hoo helps her was when she was being bullied and he was the only one to do so. Jan Di persuades Ji Hoo to go to France to follow Seo Hyun, his love interest, despite her regretting to do so. When Ji Hoo returns from France he discovers that he has feelings for Jan Di. Ji Hoo attempts to confess numerous times, one of which Jan Di falls asleep within, the second time she does not hear him and lastly he gives his mother's ring to her. Yet, Jan Di refuses because no matter how hard she tries she cannot forget Jun Pyo. Upon realizing that he cannot have Jan Di, he stays by her side to protect her whenever she needs his help.
Yi Jung and Ga Eul
Ga Eul is Jan Di's best friend since kindergarten. Ga Eul initially thinks of Yi Jung as a guy with "handsome face" who only plays with girls. Later she starts developing romantic feelings for Yi Jung after he helps her get over her boyfriend who just played with her. She realizes that inside Yi Jung is a pure and lovely person. In order to get Jan Di and Jun Pyo together, Yi Jeong takes Ga Eul on a fake date. On Valentine's Day, she even makes a present for him to express her gratitude. At first, it's obvious that Yi Jung only thinks of her as a good friend when he says he doesn't like girls that are "nice, idiotic, or involved with his friend". Yet, since Ga Eul helps him through his self-destruction, Yi Jung finds out that Ga Eul, not Eun Jae (his prior love-interest) has always been by his side. He eventually shows some feelings towards her, especially when he promises to visit her first when he returns from Sweden .
Geum Jan Di is from a poor family with a fierce and weed-like determination. She first liked Ji Hoo, who was the only one who showed any compassion while she was bullied. Eventually Jun Pyo begins to fall in love with her, and as he expresses his feelings to her through his actions, she gradually begins to reciprocate those feelings. Jan Di later is determined to pursue the medical industry after realizing she can't swim because of her shoulder. 
Gu Jun Pyo is the hot-headed leader of F4.He is the heir of Shinhwa Group, and after his father [supposedly] passes away, he inherits and begins to run the Shinhwa Group along with his mother. When he was eight,he was kidnapped by his own driver. The car crashed and plunged into a lake, and from then on Jun Pyo had been afraid of swimming. Exasperated by Jan Di's act of defiance, he makes her a target of bullying.But as time passes, he begins to admire Jan di's determination and falls in love with her. 
Yoon Ji Hoo is a calm and soft-spoken boy who likes to play the violin, piano and guitar and conduct an orchestra. Seo Hyeon was Ji Hoo's first love, after she helped him overcome trauma after the death of his parents when he was little. He attempts to fight for Seo Hyeon's love by following her to France. But then he realizes his love for Seo Hyeon was just worshipping her.When he comes back, he realized that he had fallen for Jan Di. However, Jun Pyo has already announced his love of Jan Di. Ji Hoo decides not to betray his friend by trying to fight for Jan Di. He is a grandson of Korea's former president. 
So Yi Jung is F4's perennial playboy. Handsome and gifted with a brilliant smile. Yi Jeong also has a habit for making every girl fall for him. Even Geum Jan Di's friend, Chu Ga Eul could not escape his charming ways. He is from a family of well-known artists,and is a reputed potter himself. His family owns an art gallery that exhibits national treasures. He is known for his "5 second kill" which is a technique that leads girls to fall in love with him and kiss him in 5 seconds. According to Ji Hoo, "F4's Casanova". 
Song Woo Bin, from their origin in the underground, his family now runs a prominent construction business. The family owns real estate throughout the country. He is also the very good friend of Yi Jung and a kind hearted person even though he is known as a playboy himself. Aside from his handsomeness, Woo Bin can talk American hip hop very well which, and adds a plus in his charms to the ladies. Sometimes, he is seen betting with Yi Jeong for cellphone numbers of various girls. Ji Hoo calls him "F4's Don Juan". 
Chu Ga Eul, is Geum Jan Di's best friend since kindergarten, with Jan Di, often saving her from bullies. Yi Jeong often describes her as "nice and idiotic". She is also Jan Di's co-worker, as they both work at the Porridge Shop. She eventually develops feelings for Yi Jeong and even agreed to go on "Fake Dates" with him to bring Jan Di and Jun Pyo back together. 
