Here is a manja that seems to be from the small pictures a guy getting nuts pulled by girl

http://imgur.com/1n7nBly

http://imgur.com/CWN3qh8

I have never seen this manga but it looks funny as hell (small images tho).

Here is thread where I originally found

http://fuuka.warosu.org/jp/thread/3024821

It is not a Harenchi Gakuen (i have read all) but perhaps some other Go Nagai work. If anyone knows what manga comes from I will find and post bigger pictures here.