A clumsy high school girl named Oh Ha-ni (Jung So-min) who is at the bottom of her class has had a crush on a popular and genius male student, Baek Seung-jo (Kim Hyun-joong) ever since she laid eyes on him on the first day of high school. Ha-ni decides to confess through a letter, but is rejected rudely by Seung-jo, who tells her that he hates stupid girls and returns the letter having corrected all of her mistakes.
Fate intervenes when an earthquake ruins Ha-ni's family's newly built home. While the house gets rebuilt, Ha-ni and her father are invited to stay at the home of her dad Oh Ki-dong's (Kang Nam-gil) childhood friend, who happens to be Seung-jo's father Baek Soo-chang (Oh Kyung-soo). Ha-ni's feelings for Seung-jo are rekindled, and she is more than determined to impress him. Seung-jo remains insensitive to her feelings and finds her a complete nuisance. However, Seung-jo's matchmaker mom, Hwang Geum-hee (Jung Hye-young) helps Ha-ni a lot.
During her time with Seung-jo and his family, Ha Ni blackmails Seung-jo into tutoring her to become part of the top fifty ranked students in their high school. Seung-jo reluctantly agrees and over the weeks as they tutor together, Ha Ni's feelings grow continually stronger for Seung-jo, and his feelings for her also strengthen though he does not show it and is still very confused by them. When the results of the ranking come out, Ha Ni is so proud of Seung-jo's expected #1 that she doesn't notice her own score, and when Seung-jo tells her to look at her placing she is shocked by finding she ranked #50. Their high school year is filled with heartbreak, confusion, anger and Ha Ni's unrequited love, and slowly Seung-jo comes to like Ha Ni and finds her company very enjoyable. After several dramatic events involving Ha Ni, Seung-jo realises that when Ha Ni says she will forget him and no longer likes him in front of the senior year, he panics a little and strings her along by kissing her on their graduation night to keep her interested, though she secretly still is and announces that he decided to attend the same University as Ha Ni.
Seung-jo and Ha-ni soon graduate high school and go to university. There, Seung-jo meets Yoon Hae-ra (Lee Si-young), the female Baek Seung-jo. While Ha-ni's classmate Bong Joon-gu (Lee Tae-sung) still has, despite many incidents that have continuously broke his heart, feelings for Ha-ni. However, Seung-jo is still the one Ha-ni likes, despite the fact that he is always with Hae-ra and said that he lives for teasing her. Hae-ra falls in love with Seung-jo and they begin working together at a cafeteria, which makes Ha-ni jealous.
Ha-ni's feelings continue to grow just as the friendship between Seung-jo and Hae-ra does too. When Seung-jo's father becomes hospitalized, Seung-jo takes over his father's gaming company temporarily. He is introduced to the investor's granddaughter at an arranged marriage meeting, who turns out to be none other than Hae-ra. With everything going on, it seems impossible for Seung-jo to like Ha-ni. Joon-gu also doesn't give up on trying to win Ha-ni's heart, and one day, he takes his crush one step further by proposing to Ha-ni. Afterwards, Ha-ni walks back to her father's noodle shop in the rain to find Seung-jo standing there with an umbrella, waiting for her. Seung-jo claims to be curious about her answer for Joon-gu, knowing that he had proposed, but Ha-ni refuses to tell him. This leads to an argument between the two, causing Ha-ni to have an outburst, which is interrupted when Seung-jo suddenly kisses her.
The new couple walks back home and announce that they're engaged. During their honeymoon, they encounter another couple. The woman flirts with Seung-jo in front of Ha-ni and fakes an injury so that he will inspect her (Seung-jo mentioned that he is studying medicine). Ha-ni gets jealous, and she and Seung-jo argue. After Ha-ni leaves the room, the woman tries to get Seung-jo into bed, but her male companion returns and tells them that Ha-ni had left the hotel. Then Seung-jo realizes that the woman was faking and goes to find Ha-ni.
Chris, a British-Korean girl, enters their lives. She speaks Korean fluently and has a crush on Joon-gu. But Joon-gu says he only has room for Ha-ni in his heart; it is later revealed he was in denial, and has begun to have feelings for Chris.
Ha-ni tries to switch her major to nursing to be closer to Seung-jo, but her grades aren't good enough. On her way to a date with Seung-jo on Christmas Eve, she witnesses an accident. Despite the risk of arrest if it's done incorrectly, Ha-ni successfully performs CPR on the person and accompanies her to the hospital. It makes her late for their date, but finds Seung-jo waiting for her. Meanwhile, Min-ah becomes a famous cartoon artist, and Joo-ri becomes friends with a guy newly discharged from the military who comes to her salon everyday for a trim. The finale ends with Ha-ni and Seung-jo making out in the company car.
i loved this drama espically the special eps :D i loved kim hyun joong alot :D and i really liked the couple