"Once upon a time" the famous phrase which precedes all fairy tales, from Cinderella to Red Ridding Hood, and in some way perhaps this is a fairy tale it begins with a simple set up, there is a conflict, and a happy ending. Once upon a time there existed a world where all the fairy tales you know are real, where magic was plentiful and happiness is found everywhere, (well except perhaps the villains but who cares about villains). Perhaps this is what attracted Asmodeus to our world, or perhaps it was but a whim, it matters not.
The great demon and deity of lust came to our world summoning legions of lust demons, bringing heroes to fall, and corrupting all the land, while the worlds denizens fought against him futilely. Soon Asmodeus discovered the existence of the Heart of the World the center of this world of fairy tales, and in reaching it the very fabric of the world could be changed. Heroes and even villains tried to fight against Asmodeus as they made their way to the Heart of the World, intent on creating a world hedonistic pleasure, but they failed. Asmodeus reached the Heart of the World, they altered the world, everything from its land, to its people, to its magic and its morals was changed, and thus was crafted the world of perverted fairy tales. Sex is as common as a hand shack, shame doesn't exist, nor does monogamy, and the very magic of the world depends on lust, truly a happily ever after.