I've spent so much time looking for the source of this but with no luck. I hope this is the right place to get some help.

It was originally posted 4 days ago (June 1st) on Tumblr only tagged with doujin by someone who reblogged it. I know it's not a lot of info but I'm at a loss here...

Look at that butt & that little bit o' thigh...
I'd be doing great too if i could find the dang source.