Ue wo Muite Arukou!

The story is about a girl who has constantly fighting with an orange-haired boy since the first day of high school. One day she meets Shintaro, her first love. Suddenly the orange-haired boy confesses his love to the girl. Shintaro mistakes them for a couple and thus ruins the girl's chances of expressing her love for Shintaro. (Source: Perfect Illusions)