The second set of Koryu Dai Ni, consisting of techniques #4-11 are ushirowaza - defenses against attacks from the rear. They are organized into complementary pairs, similar to Koshiki no Kata and parts of Junana Hon Kata.
In the first pair, #4 and #5, uke grasps both of tori's wrists from behind, as if trying to hold him for another attacker or to stop tori from deploying a weapon. The first technique (kotegaeshi) is distinctive because tori stands his ground and offbalances uke so decisively that uke is forced to move in front of tori.
When I first saw this demonstrated several years ago, I thought it was incredibly stupid. I interpreted it as tori obstinately standing his ground and forcing uke to run around - sort of like showing off by running the table." Then at some point I realized it was a n exercise - sort of a game to see if tori can develop sufficient internal structure to offbalance uke sufficiently while holding the foot movement in reserve. That is, it is an exercise of making the techniques more challenging by constraining tori's movement.
Next is jujigarame nage. Uke's attack is the same, except tori is unable to do the previous technique because of uke's resistance, so tori slips under, crossing uke's arms. Because jujigarame is often an onerous fall for older and heavier ukes, some toris like to release the second hand, turning the technique into kotegaeshi. Honestly, once you get uke off-balanced and his arms tied up, you should be able to think up something nasty to do to him.
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