I first typed this up stream-of-consciousness to a friend of mine via GTalk, so that's why the paragraph breaks are the way they are.
The protagonist is a normal guy in high school/college/whatever fits the story best.
He's also kind of a loser.
So, this girl he's had a crush on for a while finally starts to take interest in him.
And becomes his girlfriend.
And has sex with him.
And becomes subservient to him.
And so does everybody else- he suddenly starts getting better grades, etc.
I'm not when he'd realize this, but he's a subconscious reality warper, not unlike Haruhi.
Even when he realizes this though, he can't control it.
The world starts to seem like a dream.
I'm not sure where I'd go from there, but whatever happens would be very fucked up, mind-boggling, weird, and very, very, interesting.