Add some 18+ mods for your game. We all hear about law in South Korea. No one talk you to official add it to your game. Just make it like a mod and dont sell it - just upload to nexus mods. Why we buy your game and then must search for mods that some people often sell on petreon. Really - if you respect your target audience, just make this simple thing. We don't have to pay twice.
There are no laws that would punish you for third-party mods on foreign resources for your games.
It looks like you don't care about the fans of your games.