From Baka-Tsuki:

The story revolves around Kinjirou Sakamachi, a 17 year old high school boy who suffers from gynophobia. The sickness known as gynophobia makes his nose bleed every time he has physical contact with a female. While using the bathroom he accidentally discovers that the popular and handsome butler, Subaru Konoe, is in fact a girl.

Now that Kinjirou knows about Subaru's secret, he must work together with Subaru and her sadistic mistress, Kanade, to protect Subaru's secret from being discovered.