There's never a "good" place
Depending on what you're trying to accomplish and how adult your story will be (and with how borderline risky sexual themes), there are several places where you could try posting other than simply creating a form of a blog and writing there.
While adultfanfiction and fanfiction.net both do allow for original stories without a 'fandom' to attach it to, I believe you'd find that the latter has a lot more restrictions on posted content and the former tends to be both problematic in regards to getting feedback/being rated, and varying wildly in quality of writing present there.
If you want to try places that allow for adult content and are specifically designated to post stories, I'd suggest getting onto an invitation line on Archive of Our Own (I recently registered and started posting there, and am satisfied so far), or registering on FicWad. Both places have a mix of 'Original" with "Fanfiction" content that is pretty balanced, and as long as you sufficiently warn your readers about what they're supposed to expect, there's a "Whatever you want to write and read, goes" policy. The tagging system on AO3 is a bit of a pain, but is also highly accurate with what you want to describe while being very broad in apllication in terms of readers finding your stories through it.
Finally there's always Literotica. I doubt things could go wrong for you there. There are some limitations on content that personally make me unable to post my own works there, but the things you described on here I've all seen mentioned or actively read there.
