I've got an idea for a game based partially off the anime Sayanora Zetsubou Sensei, except vampire flavored. The premise is that there was a spirit in Tokyo named Shen Zetsubou. Zetsubou was a neurotic man in life, and even worse in death. His blood was tainted, turning him into a walking corpse who needed the life force of the living to sustain himself. Mired in his madness, he sought out companions, driving them to madness by grinding away at their flaws, eventually feeding his blood to them so that they joined the ranks of the living dead, often as they commited suicide.
Each companion brought him joy and peace for a time, as he fed more of his blood to them, to force them into becoming utterly devoted to him, yet with each ghoul he sired, he gave in more and more to his despair. Now Zetsubou is a man with nothing left, a spirit who can have no hope. And yet, he's got a harem of utterly crazy maniacs, many of which have their own sexual obsession with him. And, of course, there are those in the harem that want others in it as well as Zetsubou Sensei...
The game is quite open to both males and females, of course. :)
Some example concepts ripped from the anime: (from left to right)
Foreign girl who doesn't understand why people keep calling perfectly edible food "garbage"
Fanfic writer who is obsessed with discussing every possible sexual pairing between the characters.
Glamorous, beautiful girl who takes offense at everything because she believes others view her as a sex object only.
Obsessive compulsive girl who needs everything perfect.
Girl with an insanely dangerously optimistic outlook on life.
Clingy, stalker personality girl who imitates her current crush as closely as possible.
Agoraphobic, chlaustraphilic girl who only feels comfortable wrapped in a heavy cloak or blanket
Girl deeply enmeshed in the furry fandom who has a fetish for being mauled by wild animals due to a masochist streak.
Shy, mute girl who only communicates through electronic communications... on which she is incredibly rude.
Normal girl who goes completely batshit at the prospect of being called "normal" considering the kind of company she keeps.