An old creep dude, who watched strange porn all his life, dies. The Devil offers him a deal: he was such a promising sinner, but wasted his life never doing anything of his dirty fantasies. So, instead of going straight to Hell, he can live his life once over. Go back to the day when he was 14.
More so, he'd have his life improved. He would be very healthy, full of energy to act on his desires, he will have some abnormal luck avoiding big dangers. Probably a small superpower or two.
All he has to do, is to be that dirty perverted sinner he was in his dreams. No, he won't have a "completion scale" like in video games, he'b up to his own decision. But if he does really well, then the Devil will give him some bonuses. Probably.
And when his life would be over again, he'd go to Hell, but would join the ranks of demonic creatures, not poor tortured souls. Or even go for another round. Most unlikely, but not impossible.
The dude agrees, but, as all deals with the Devil, there's a catch. And he wakes up in the body of a girl.