The Doujin specializes in content of an adult nature with a particular focus on anime and hentai releases. Yeah, I think you know what I'm getting and if you don't, head elsewhere before you get scarred for life by delicious dickgirls that want to take it in the butt while you jerk them off.
So the futanari section here updates quite regularly and has a lot of original Japanese releases. Translations seem fairly common, but not all of them are available in English. I counted over 1,200 full-length publications in the archives just in the futanari sections alone - if you spread your search a little further and look at content they have listed in other areas, this multiplies quite a bit. If you happen to be interested in general hentai, this place certainly serves that purpose as good as any other destination out there.
With better search features and more translations, I'd be very happy to recommend The Doujin as a top-tier hentai source.