Sexfight World

In an alternate world where sports and sexuality have developed side by side, combat sports have been replaced by competitive forms of sex, in which—in addition to facing off with punches, kicks, and holds—the two opponents focus on winning sexually by bringing their opponent to orgasm or by reaching orgasm themselves using their opponent’s body.

Edit: I want to point out that in this world biologically, men and women have developed to the point where they have similar criteria of physical and mental strength and energy, while still maintaining a virile social and personality status in men and feminine in women, with some exceptions.
This means that while men are still physically stronger, the gap between the sexes is a lot smaller then it is in the normal world.