Re: Kokyu - Ueshiba vs. Sagawa
There's some interesting things there, at least to my eye.
Sagawa looks like he's deflating uke - letting the air out. Depressurizing.
Ueshiba looks like he's inflating uke - putting the air in. Pressurizing.
But a little trick here is that Sagawa - in the frame - is probably just a bit early in the movement, closer to initial contact. He's about 10 degrees off the line. That would be in a safe "dead" zone to receive uke. Ueshiba is closer to 30 degrees off the line.
Now, a few things we do know. You can't let air out of something that doesn't have air in it. And you can't inflate something that has, at least to some degree, been partially deflated. You also can't inflate something if you have no desire to do so. Or if you've been taught to deflate it and discard it.
From everything I've seen of DR, they really do initially shock uke - like putting a nail in a tire. And from there, they pretty much destroy it. And there's always that last "fuck you, you're dead" chop in DR.
To me, Ueshiba does seem to be developing aikido here. Because, while he recieves uke, Ueshiba has enough breath for both of them. So, Ueshiba's saying, "Hey, even though you come at me with a fucked up attitude, not only am I'm not afraid that you're going to take my breath, but here - let me give you some good clean breath so you can be made whole again, and go about your business. And maybe with a little better attitude.
If we're looking for "roots" I'd say Ueshiba was showing more CMA than DR. CMA has Aiki. DR didn't have Aiki - even in it's name - until Ueshiba used it and Takeda coped it.
Ueshiba shows a clear progression to an art that gives life rather than takes it.