I'm mostly on nhentai, but these are the longer ones I like (at least 3 chapters, usually a lot more). I'm not recommending anything more extreme unless that's what you want:
- Shiritagari Joshi: young women exploring anal. Ending isn't that great though
- Watashi no Shumi tte Hen desu ka: sweet lesbian story
- Enkou Ojisan: A bit of comedy, surprisingly entertaining
- Muramata-san no Himitsu: shorter one here, for a very specific thing involving a tongue
- Inou Joshi Ueshima: Actual legit storyline, treat this like a shounen manga
- Kashiwazaki Miki wa Ironna Basho de Zenra Sanpo Shitemita: girl exploring exhibitionism. Story is meh.
- Please! Freeze! Please! (by Shiwasu no Okina): 3 friends learning about sex together.
- A Pervert's Daily Life (by Alice Crazy): completed webtoon, this one is 70+ chapters. Ultimately, it's a vanilla.
Erotic manga I support Nozoki Ana and Nana to Kaoru.
Last: if you want excellent sex scenes and even better storyline, there's an English webcomic called Alfie, it's on buttsmithy.com. Still ongoing, 900+ pages medieval fantasy. Main page on the site is always the most recent page, so careful of spoilers.