Haruka Nogizaka's Secret(2008)

Nogizaka Haruka no Himitsu

The story centers around Yuuto Ayase and his classmate Haruka Nogizaka. While Yuuto is rather ordinary, Haruka is very attractive, intelligent and rich. Due to this, she is the school's most unattainable girl and is so idolized that her classmates give her the French nicknames "Nuit Étoile" (The Silver Star of the Night) and "Lumière du Clavier" (The Shining Princess on the Piano). One day, when Yuuto goes to the school library to return a book, he stumbles across Haruka and her darkest secret—she is a diehard fan of anime, manga and the otaku culture. Yuuto promises to keep her secret hidden and the two become close friends. Yuuto does his best to help Haruka with her secret hobby while developing his relationship with her.

(Source: Wikipedia)