While wondering about what his life will become from now on after being fired from his part-time job, Yukiya found an unconscious beautiful girl leaning against the trash can behind the store. When trying to help the girl, he is attacked by a homeless beggar. On the verge of dying, he suddenly revives after drinking blood from the girl's finger. Next time, the girl drinks the blood from his wound and get a little better. He then decides to bring the girl home with him since she is still weak.

Later, he learns that the girl is actually vampire and he is now in incomplete state of vampire conversion after drinking her blood. The girl offers to bring him back to human in exchange for him to be her servant and help to recover her power in 7 days. However, she dislikes sucking blood from human so he has to dedicate his semen instead ???