Ouran Highschool Host Club Kasanoda

Because Kasanoda has a habit of bursting into rooms without advance warning, he walks in on Haruhi as she is changing and learns of her true gender. He had a confused crush on her prior to learning this, but after her "reveal," falls in love with her.  Being unaware of the actual reason behind Haruhi's cross-dressing, but determined to protect her at any cost, he swears to protect Haruhi's secret.