The main character is Yukino Miyazawa, a Japanese high school freshman who is the envy of her classmates because of her good grades and immaculate appearance. However, this is just a charade she maintains to win praise — at home and in private, she is a somewhat mean-spirited slob, who studies relentlessly instead of spending time with her sisters. Her position is threatened by Soichiro Arima, a handsome young man who also gets top grades and unknowingly challenges Yukino for class leadership positions and the praise she lives on. She vows to destroy him, but after some misunderstandings they see past each other's facades and fall in love instead. The series follows their relationship as they are tested by school, family problems, and friends.
source: http://en.wikipedia.org