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 a vampire, but vampires are 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.