Lunar Marked is really good if you don't mind trangender themes.
The Chimeric Ascension of Lyudmila Springfield is also pretty good. It's not tagged as smut or ecchi, but it has a lot of sexual content if that matters to you.
Succubated is a little different, but has quite a few content warnings as well. I'm recommending it mostly because of "succubus, demon". It's also smut.
And the last one is Vigor Mortis (It's on RR, on Scribble Hub there's like ten chapters). The gender bender part doesn't come in till you're like ~80 chapters in, but it's a really good story overall.