No anus is exposed, and in a lot of this doujin, he doesn't penetrate her. I think he's just humping her ass cleavage.

As in thrusting his penis in between her ass cheeks?
I believe it's called hot-dogging. AerisDies.com has a section in the Random Hentai section about it.

And I do believe you're right.

Then edit the tags, ScallionNegro.

rapidshare?

We need a source.

Cyrus said:
We need a source.

http://www.fakku.net/doujinshi/holonbu-japanese