Well, I'll start by saying that I've learned on this board that NTR means different things to different people. I'm not into shaming, humiliation, BDSM, or anything along those lines. However, I am very much into swinging, sharing, group sex and other consensual sexy activities very much.
So, my idea game would be:
- Sandbox, without question
- Graphics could be 3D, Honey Select, or really well done hand drawn (like Summertime Saga or What a Legend), not not flat 2D anime style. I don't like that at all
- The MC would be at least average height, fit build, and with a big (realistic) cock. He'd be a fairly confident and comfortable adult.
My setup would be that a young couple in their 30s moves into a new neighborhood. The MC and his wife are both fit and attractive and have a good sex life. They make friends with their new neighbors, a couple about their age who are both really hot, beautiful people. The MC and his wife are both immediately, but privately, attracted to the other's spouse. They get to know them better over a short time, hanging out at each other's houses, drinking, and spending time in their neighbor's hot tub, and become very comfortable all together.
At this point, they learn that their neighbors are popular amateur porn stars, and have been doing it as a way to add spice to their life and make a little extra money for a few years. The MC and his wife talk about whether they want to check out their porn online, and after some back and forth, decide that they do, and are both very turned on by what they see. The sex is really hot, and they immediately realize that their male neighbor has a really big cock.
They decide to talk about it with their neighbors, and after a few drinks and everyone is comfortable, the neighbors become bold and ask them lewd questions about what they liked and how hot it got them. When everyone is turned on, the neighbor couple makes their move, and simultaniously innitiates sex with our MC couple. They look each other in the eye, and nod, and there's a hot swapping sex scene where everyone has an awesome time. The wife is now addicted to sex with the neighbor, and needs a lot more of it.
This would be where the game opens up, and transitions from a VN to a Sandbox, with the player controlling the MC and making a variety of choices. The male neighbor, encouraged by his wife, makes an offer that they want them to join them in making porn. Our couple have to decide how they feel about this, how they want to react, and how quickly to be excited - or not, about the whole thing.
The MC's wife is ABSOLUTELY GOING TO GET FUCKED. The question is, how you play around that. Is the MC a cuck spectator, or does he get involved himself? The gameplay would involve around him needing to get more fit, more confident, and improve his sex skills if he's intent on keeping up with his wife as she gets into porn, or gets left behind. He would need to maintain his relationship with her, both sexually and otherwise. He would need to maintain his friendship with the neighbors, to stay in the loop and keep tabs on what is going to happen next and how quickly. And he would have the ability to explore the city and people he knows and gets to know, and given that he is now in an open relationship, he can seduce and fuck women and persuade them to join their new porn company, and chose to see if his male friends want to participate as well.
The challenge would be keeping the MC's stats up while balancing everything else that's going on, and choosing to bring the right outsiders into the porn world that they're creating, because the wrong ones could mess things up in a variety of ways. Can the MC and his wife become the next big porn stars and live a life of wealth and sex? Or does he end up losing her along the way and get left in the dust?