I'm pretty disappointed with the concept of it being a game they're playing rather than Luna being an outright fantasy world, but I'll save deeper thoughts for when the actual thread is made. I don't think there's anything inherently wrong with it but it's always felt disconnected to me and quite tricky to actually write for, although there's quite a lot of opportunities if it's utilized correctly. I hope the real world content ends up being more than just an afterthought and ends up getting just as, if not more fleshed out than the RPG.
The concept of it being BSS rather than standard NTR is interesting, and I'd love if it were made this way in order to allow more routes for the player to choose, e.g. True love, dating which turns into actual NTR, staying as friends and watching another man/men date her instead as a third party member. There's a ton of potential to be had here and I'm excited to see how this progresses. Best of luck to Headpat and his artist.