Nogizaka Haruka no Himitsu is set at the private high school Hakujo Academy in Japan and centers around the male protagonist Yūuo Ayase and his classmate Haruka Nogizaka. While Yuto 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, Yuto's good friend Nobunaga Asakura asks him to return a book to the school library, and when he goes to return it, Yuto stumbles across Haruka and her darkest secret — she is a diehard fan of anime, manga, and the otaku culture. Yuto promises to keep her secret hidden and in return he becomes her confidante of sorts as he accompanies her to Akihabara, and visits her home often.