This post contains some pornographic contexts. Viewers’ understanging is required.
There are a lot of, full of outrageous mysteries in otaku world like やおい穴[yaoi ana]. Yes, this is something the exact opposite of the mysterious hole…that is ふたなり[futanari]. In doujin circles, this is a very famous way to create yuri manga, I mean, when the two girls do it, either has to function as 攻め[seme](I heard you say top and bottom in English, but does this work as the same way when it comes to lesbian?). In that case, it needs a male sexual organ if they don’t have an oral sex or use any adults’ toys…she might have a real…あの…えっと…penis. I don’t know if it’s real or a fake because there’s always no explanations why she possesses it. If you make a yuri doujinshi, by all means explain it, please. At any rate, if she is bisexual biologically, it shall be called as ふたなり[futanari]. A bit more difficult saying is 両性具有[ryousei guyuu]. Having said that, it doesn’t even necessarily mean she is such an 俺女 just because she is a futanari. Rather we are seen those girls are quite feminine. This happens not only in doujin, but in the porn video. Actually I accidentally came across such a porn video where an actress who acted Suzumiya Hahiru…orz. At any rate, this becomes a crazy fantasy especially when it happens in doujin manga. For example, it might be extremely huge (yes, sooooooo big! impossible!), erecting all the time(awesome!), and capable of shooting too much cum(no way!).
One more thing, this is an irrelevant note, but when I mentioned 女装ショタ[josou shota], I couldn’t stop but wondering why only a penis is so mature. As for Boku no Piko, a boy named Piko must be 10 years old or so(How old excatly is he?). Even though it gets censored, it looks so mature. That’s very weird. It’s almost the same size as an adult’s one. Umm, like yaoi-ana, futanari is another enigma?
Oh, never mind.