He is an ancient vampire, decadent, sensual, and amoral. To forestall his looming ennui, and to try to gauge the pulse of this age, he has decided to expand his family by embracing a new mortal. But first he must break her, remake her, pervert her, and seduce her. It's far more entertaining to prolong the agony and ecstasy, to draw it out and savor it, than to finish quickly.
One of his childer found the perfect opportunity for him. A bus, on it's way to "Church Camp". A group of young adults, ripe, full of raging lusts, all bottled up and buttoned up, trying to obey a puritanical interpretation of their religion. Hell, they're probably all still virgins. The perfect fruit. The perfect victims, to be sucked down into a world of depravity, lust, blood, animalistic cravings, violence, slavery, and rape. Once they've been misused enough, set against each other, it will be fun to see who they really are once society's false veneer has been ripped away from the animal within. Out of the lot, there's probably at least one that will be worth the effort to degrade fully, to reward at the end with unending unlife. And if not... it will still be a fun game to play, and push away the crushing ennui of centuries.
The setting is loosely based on the old World of Darkness vampires. Familiarity with them isn't required, but it would give you a better idea of what to expect. I understand that they're also quite similar to Ann Rice's vampires. I'm not using a system; this will be freeform.
This game will go into the Extreme category. I expect there to be some pretty horrific things that will happen, possibly including mutilation and torture. And when you're dealing with vampires like these, they can do things to a body that shouldn't be survivable, then give you some of their blood, and then heal you up before you perish. But the point here is the corrupting nature of the vampires. They might be sadistic, and might do horrific things, but the point is, they're trying to find someone to join them. Well, it's possible that family politics might get involved too, so there's always a chance that one or more of the family will just be extra cruel because of some political reason. But this isn't torturous cruelty just for the sake of torturous cruelty - this isn't like being abducted by a serial killer that likes to torture his victims to death.
I don't have very many specifics planned out regarding this story, so we'll see where inspiration takes us. I tend to reflexively and strongly take the lead in one-on-one games, probably from having GMed a lot of RPGs with only a couple, or just one player. It's just instinctive for me to think in terms of where to take the story and what to do with the plot. I'm only mentioning this, because it might rub some people the wrong way. I don't mind collaborating, but it delights me when I can get that gasp of surprised or shocked joy from the person I'm playing or writing with.
For the sake of my partner, I will presume that your character is either the one he is most taken with, or the one that seems most likely to be embraced when this is all over. All the other people on the bus will eventually be killed in the course of the story. I also won't guarantee that your character will survive. It's possible that they won't survive.
I don't have a firm number of people that were on the bus. I'm thinking something like a total of ~7 people, including the driver, assuming ages of around 18-19 (but probably older for the driver), but I'm a little flexible here (I just don't want to go too old, because then you're a lot more likely to find that your "good church kids" have had sex, experimented with alcohol or drugs, and so forth).