Based on the shoujo-ai game by Caramel Box. The main character Mizuho is a nice guy who was born in a good family, smart, and moral. But one day, he has to transfer to a girl’s high school by his grandfather’s last will. Then, he has to disguise like a girl to go to the school… Taken from Animenfo. The guy dressed up is the one on the bottom right. Red head seems to be some kind of osananajimi.