Role-playing games with adult (as opposed to Young Adult) themes

A bit off topic I suppose but I still remember how much power the word “adult” had for me as a youngster. Everything interesting to me seemed gated off, and the grownups had the keys to the kingdom. What were these “adult situations” I would see referenced in movie ratings? I still recall the feeling of profound disappointment when someone explained to me what an adult arcade actually was. I’ll leave you with a part of an old Elvis Costello song -

Why don’t you tell me about the mystery dance
I want to know about the mystery dance
Why don’t you show me
'Cause I’ve tried and I’ve tried, and I’m still mystified
I can’t do it anymore and I’m not satisfied