Soredemo Tsuma Wo Aishiteru - Ep. 1
Another case of more sound rather than show, though.

16:00 - Girl shits into the toilet (heard) while being filmed by a guy, who then fucks her over the toilet.

18:00 - Apparently more comes out of her ass while getting pounded, but of course this isn't shown either.
19:40 - You finally manage to get a quick glimpse of it in the toilet though :)