Park Min Gyeom is a human with a disease called hemochromatosis which causes his body to regenerate blood faster than normal. Because of this he often donates blood, but one day he meets someone who needs that blood even more. Meet Kim Chun Sam, a half vampire who also happens to be a classmate of Gyeom and needs human blood to survive.
Sam first bites Gyeom out of desperation, but Gyeom admits that since he has extra blood it would not be too much trouble to lend some. The agreement makes them a strange pair of friends and as the two spend more time together people start to assume they are in a relationship. Gyeom denies this, but there are some feelings that cannot be ignored.