Sensei! 

Hibiki Shimada, a normal 17-year old high school student, still does not know how to fall in love, although she's surrounded by "experts" in love. Until one day she realizes that she's fallen in love with her hot and nice 26-year old sensei (teacher), Itou. She then takes a path to make her teacher understand how she feels for him. Note: Includes 3 extra chapters.