Yuuki grew used to living alone after his father died. Yet now he's living with a girl named Mikage who appeared before him and settled down in his home. Mikage just happens to be Vampire, but vampires a little different from the legends, since what she drinks isn't necessarily just blood and she can walk under the sun. Now Yuuki has to live with this vampire--and to his surprise he has antibodies against vampires that prevent him to be transformed. But because he is living with a vampire now, sometimes he gets attacks that increase his sexual desire several times--and things get worse when he learns there are others vampires besides Mikage...