Shiroi Mado no Mukougawa

Seiko is a normal girl with a tendency for daydreaming, and Yoshito's a fairly sensitive, subdued boy. They've been close friends since grade school, and now that they're in high school, their feelings for each other become complicated. Though all of the diverse array of characters in the story seem to see it as plain as day, Seiko does not realize Yoshito would like to be more than friends.