Quite a number of the stories in Thinking Horndog's "Swarm Cycle" will probably fall under your criteria, though many may not be labelled as such. You can find the series homepage here: http://storiesonline.net/universe/289/the-swarm-cycle.
If you haven't read it, the basic premise is that a hostile alien race is going to attack Earth in about 10 years and only a limited percentage of the population can get off of the planet, even with help from friendly aliens. The emigration program designs a new social system made up of Volunteers (people who meet certain criteria of intelligence, aggression, and responsibility, called CAP) and Concubines. The higher your CAP score, the more concubines you get.
So the entire premise of the universe is of a new human society based on sexual slavery. Coincidentally, men tend to have higher CAP scores than women. Consent is debatable, since once locked in to a "marriage" concubines lose all rights, but all concubines do agree to the arrangement beforehand. Of course, the alternative is being eaten, so it's not a great choice.
It's a shared universe, so the quality of the various stories varies wildly, as does how well a story adheres to the original set up, but it's a good starting point for stories that might fit your requirements.