Seemingly ordinary office employee Kim Doyoon has a secret he can't tell anyone: he's actually a half-vampire whose body can't handle drinking blood, so he survives by absorbing the sexual energy of humans. He hasn't "fed" in a while and his health is starting to decline as a result, so he decides to go looking for a new sex partner - and accidentally propositions his boss! Now the smitten company director Lee Kangwoo has decided that the two of them are dating, but Doyoon's condition continues to deteriorate in spite of having found a new partner. Kangwoo is determined to find out what Doyoon is hiding, but what will happen if he discovers his subordinate-turned-lover is not exactly human?