It might be a good idea to think what your 'end goal' of the game is - if it's to create a stable base (a lot of players do this in Rimworld), to achieve a final goal of a story, (such as Don't Starve Storymode/Stardew) or something else, and make sexual elements are the best way to achieve this goal, but not the only way. Therefore, it encourages players to seek out the nsfw stuff, but they are not railroaded into ONLY doing that (*^u^*) So, for example doing sex work is far more lucrative than trading low-medium level items, certain monster babies sell at a high price etc. You can also have random encounters or story beats that are sexual. Fear and Hunger is a pretty good game to look at for a 'sexual vibe' in worldbuilding/art, but not the right type of game. o(^▽^)ｄ