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 called 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 rudely rejected by Seung-jo, who tells her that he hates stupid girls and returns the letter, having corrected all of her grammatical and spelling mistakes and giving her a mark of D-.  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 and becomes determined to get the two together.  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, Seung-jo tells her to look at her placing and she is shocked to find that she ranked #50. Their high school year is filled with heartbreak, confusion, anger. Ha-ni's unrequited love remains but slowly and gradually, Seung-jo comes to like Ha-ni and finds her company very enjoyable. After several dramatic events involving Ha-ni, Seung-jo grows closer still to her. When Ha-ni says she will forget him and no longer be interested in him in front of the senior year, he panics a little and strings hWatch drama online for free.