A SpeculativeFiction subtrope of AuthorAppeal, which is the deliberate creation of a future (or alternate history, or fantasy..) society in which the author's particular kink is "normal". That which is FetishFuel to us, is a commonplace to those in-universe.
The difference between this and basic AuthorAppeal is the compulsion by some authors to justify their fetish. Creator/QuentinTarantino having lots of shots of feet in his movies is AuthorAppeal. If he made a movie that explains how in the year 2525 ''everyone'' will be a foot fetishist due to some social or technological development, that would be a FetishFuelFuture.
Used a lot in written erotica. Also some porn movies but not as much as you'd think, given that typically porn movies are PornWithoutPlot and thus don't even bother with a story to the sex.
Is sometimes used to "justify" the depiction of [[RomanticizedAbuse behavior and social structures]] that would otherwise push the characters over the MoralEventHorizon. (Although it can still make the world [[CrapsackWorld crapsack]] or [[CrapsaccharineWorld crapsaccharine]], and make some people suspect that the author actually [[AuthorTract advocates such values for real]].)
Sometimes characters of a Fetish-Fuel Future will [[YourNormalIsOurTaboo consider the "normal" sexual practices of visitors to be taboo]].
See also FreeLoveFuture.
'''No examples, please.'''