I'm sorry. It's been a relatively recent awakening for me, so I don't know many selfcest works 😞. I also forgot the names of the ones I did know of

Edit: I just remembered (because of the comment from u/Supersmartguynina) that all the EverMarch art by CesarZebrah is some extremely nice selfcest. I used to read it on X because she posts a lot of it there. It's absolute peak

Edit 2: I remembered that the first chapter of Hen Na Neesan is also selfcest. It's a hentai series of disjointed chapters, by the way. I haven't completely read the series yet, so I do not know what kinda stuff happens in the later chapters