Actually, I am...

Asahi Kuromine, a seemingly unremarkable high school student, finds his demeanor swiftly put to the test when he sees Youko Shiragami unfolding a sizable set of wings from her back. He discovers that Youko is a vampire and that her admission to a regular school is contingent upon no one finding out about her actual nature. Since Youko is an airhead and Asahi's childhood friend Mikan constantly picking on the two of them, keeping this a secret gets challenging. Asahi struggles to keep Youko's secret as he learns about other females at his school who have secrets of their own, including a small alien who rides a human-sized exoskeleton of herself and a werewolf with the ability to change gender at the sight of any moon.