From the PDF:
There is a kind of magic in the world that no one speaks about. It can sway the hearts of men and women, control their every thought and deed.
It has mastered kings and brought down nations. And yet, it is so subtle, its power is nearly invisible.
And the magic is sex.
Sexcraft is a Little Game with a Lot of Sex. It is a meta-game (much like The Flux) that you can place over any other roleplaying game.
It is a game for consenting adults.
Also includes the D20 Prestige Class: The Sexcraft Witch.