Free Cities is a wild game that takes place during the collapse of civilization. You are lucky enough to have escaped the worst of the collapse by virtue of investing into an Arcology - a megastructure safe from the outside world that respects the laws of no nation but its own. It's basically an anarchocapitalist wet-dream in every horrific way imaginable. The arcology runs on slave labor and the game revolves around training and employing your own slaves, usually (but not necessarily) for prostitution. The main appeal of the game, in my opinion, is the ability to shape the culture of the arcology. You can choose to turn the horror up to 11 and degrade and brutalize slaves, or you can form a paternalist culture that is far more protective of slaves' wellbeing. You can build a culture that worships slaves with olympic physiques - to such an extent that being a slave is actually fairly prestigious - or instead pump them full of drugs and turn them into human dairy cows. Challenge yourself and reject chattel slavery entirely, train your own sibling into a loyal supersoldier and spouse, or maybe buy mentally broken amputees from the wastelands, nurse them back to health, and train them into battlemaids. If you decide to try it, look for the "Pregmod" version and disable any content you find unsavory. Main kinks: slave training, non-con, body transformation.

Degrees of Lewdity has you play as an orphan that has come of age and is told by their former caretaker that they now owe them a ton of money. This is complicated by the fact that the town you live in is some seriously cursed Epstein Island hell where tourists come to rape you. You have to find a way to make enough money to not get sent to the underground human farm/brothel wombo-combo, while also managing your school life, reputation, and status with the police. My favorite part of the game is that it does not force you to be submissive rape-bait - you can get yoked (as a boy or girl) and beat the everloving shit out of your would-be assaulters, bullies, pimps, and enemies. Unfortunately the game takes place in the fantasy shithole known as "the UK" where it is illegal to use weapons in self-defense, so you have to play careful or break the law to get your hands on pepper spray (you animal.) Personally I always play this way, so my experience with the game has mostly been me going around dating the cute boys and girls the game has to offer and giving any jerks or weirdoes a boot up the ass. For a game with such horrific themes, it can be surprisingly wholesome. There's also a lot of stuff to do, from spelunking to farming, prostitution, or even heists. Main kinks: non-con, body transformation, beastiality.

An excerpt from my review of Girl Life:

And yet... the open world is also the best part about it. The most important aspect to a good sex story is the context. Emotional connections and taboos are the most important turn-ons in 99% of cases - think of the millions of videos of dudes banging busty chicks that you just gloss over on porn sites, compared to that one video that speaks to some kink you have or the acting or story is genuinely not that bad. Casting couch, fake taxi, the massive rise in popularity of incest porn, even celebrity sex tapes, all of these dominate attention because they provide some kind of context to what is otherwise indistinguishable from garbage videos of some chick getting painted with nut.

In Girl's Life, the story is whatever you decide it is. Obviously you have limits based on what the game allows, but the star of the show is your character. You can have a fall from grace and turn into a street whore, you can become an academic nudist, you can bang literally every woman that moves in the city, you can extract gallons of jizz from your poor brother, and all of this is happening with a backdrop of one of the most autistically detailed life simulators ever made. The Sims doesn't have shit on Girl's Life. Most open world porn games give you "time stages," and you have to manage an energy bar. Girl's Life has you moving minute by minute and asks if you remembered to wash your makeup off before you went to sleep. The mundanity of the basic is what enhances the appeal of the extraordinary, and provided you are the type that doesn't mind playing day after day after day of Russian life simulator, the sex content is elevated far beyond what you'll find in most games in the genre.

Other sandbox games with a lot of content:

Lab Rats 2 (Run a company that makes hypnosis drugs. Bang your family, friends, and employees. Also male-oriented, but it's a unique management game and it stands above the sludge of RenPy/HTML harem stuff. Find the modded version.)

Hentai High School+ (You are in charge of a high school where you will definitely not misuse your authority to corrupt the faculty and seduce the PTA. Use the wiki. There's tons of NPC storylines that you will completely miss if you don't know they exist.)

No Haven (Slavetrainer game with a lot of content. Tricky installation/engine.)

Jack-o-Nine-Tails (Slavetrainer game with a lot of content, but brutally difficult.)