I don't know why they are talking about vampire, they are not vampires but incubus. If someone don't know what is is: it's a demon who eats sperm.
@07-yaoi
Wwwwweeelllll actually, an incubus just tried to impregnate his victims. They would come to their victims in a dream and have sex with them. They didn't technically feed off sperm. In lore this is how Merlin was conceived. Originally though, they were a type of demon that sexed people up in their sleep and slowly killed them. The lore was made to write off ecchi dreams and sleep paralysis. Of course, rape could also have been covered up with this as well.
http://www.mangago.me/read-manga/acid_flower/mf/v01/c003/15/
XDD oohhh myyy goshhh. Lmao. That is the wierdest type of vampire.