Pic not related at all. A couple of years ago I found a doujin (no idea which site) where this guy was tutoring a girl and she was teasing him so he went to the bathroom to jerk off. Her sister ended up walking in on him and they started fucking. Then the other sister walked in and got cum sprayed on her face and they all ended up fucking. I think the mom may have eventually joined in, too.
not the same one you're talking about, but Sweet and Sour by Yakiniku King may be a doujin up your alley