Ume ni Uguisu

Umehara is suffering from an unrequited crush on a boy in her class, Isezaki. He sits directly in front of her, and she spends a lot of her time observing him and writing down her thoughts in a little notebook devoted entirely to him. Naturally, this situation can't last for long, and sure enough, things change when Isezaki forgets his notebook one day, and asks Ume if he can borrow her notes. Ume, totally dazzled that Isezaki actually SPOKE TO HER, hands him her class notes... only to realize she gave him the wrong notebook! (Source: Mangamonster.net)