Bokura ga Ita

From Hanashi:

The start of high school life. To the girls, that also meant the start of their love lives. For brand new first year student, Takahashi Nanami (Nana for short), it was no different... She happens to end up in the same class as the incredibly popular Yano Motoharu, who rumors say that two thirds of all the girls are guaranteed to fall in love with. But will that hold true for Nana, who says that if she had to choose between like or dislike, she'd say she dislikes him!?

Note: Won the Shogakukan Manga Award for shoujo in 2005.