Re: does nikyo hurt?
Hi Mert sorry for the delay in response. The picture you posted is exactly what I described. What I meant to describe was something different. But what you posted was better suited to the discussion at hand so I shut up for a bit (as my familiars will tell you that is not an easy thing to do, which was some profound ki extension on your part).
What you posted we don't really train as a formal technique, but I find myself reflexively going to this on occasion. Particularly if a same side technique is going south on me, I can often give a little whip of the arm while stepping and click into the right alignment to destabilize uke. If the lock is solid take them down, if it is transitory I enjoy the kuzushi and use the opportunity enter into another technique. I use a soft palm rather than the edge of my hand, but I think potato potahto applies here.
What I failed to explain in my original post, is nage's hand wraps the forearm from the inside in a vertical nikyo/sankyo hybrid (twisting the arm/qua open rather than closed) it still locks the elbow and shoulder and ends in a sumi otoshi-esque throw. Again, upon reflection, many would argue this is not even remotely related to nikyo due to the opposite direction of rotation (probably has it's own name), but I see some common principles; then again that is just my take. Your photo was more applicable to the discussion at hand.