Fly High (2006)

Original title: 사랑하니까, 괜찮아

It's school festival day and Min-hyuk is busy dancing and singing. However, it is not the stage but a toilet that binds his destiny. He is bewitched by a daring high school girl, Mi-hyun, who comes into the men's room because the women's room is full. From that day on, Min-hyuk woos her, escorts her home at night, stuffs her locker with roses, and clears passages for her in the morning after a snow fall. For all his efforts, he doesn't get much more than a tender glance from Mi-hyun. When she suddenly vanishes "sorry" are the only words she leaves behind.