This is the one I was talking about. This is from the first episode of Otome Chibaku Yuugi: Kutsujoku Baigaeshi ADV. A girl and her boyfriend got black mailed by a guy into going to a hotel. The guy brings the girl into the bathroom, chains her hands to the shower stand and gives her an enema while her boyfriend is tied up and watches. The shiting happens off screen. It happens around the 20:00 mark. :)