KOKYU-HO as KIHON:
Turn inwards towards aite’s side or flank. Making the wrist that has been grasped the pivot-point, “lower your shoulder, elbow, koshi and have a strong feeling of ‘down'” * and [you will find that by doing this] your structure becomes organized in such a way that you are able to swing your arm upwards and hold it high.
At the time that you execute the throw, take a single step circling inwards towards the rear of aite.
This training is a lot less easy if you are putting force into your shoulder, or if you are focusing on the hand or fore-arm that has been taken.
* Kuden from O’Sensei
– – – Traditional Aikido vol. 3, p.30
In kokyu-nage, the way you twist your koshi from hanmi is particularly important. Of course, since other waza, too, are impossible without that twist of the koshi, a deal of investigation and repetition are essential!
It is easy to see – in fact, you can perceive with a single glance – when someone has not been training enough in kokyu-nage. It’s obvious because their koshi is not as mobile as it should be, and isn’t doing much….
– – – Takemusu Aikido vol. 4, p. 13
TACHI-WAZA KATATE-TORI KOKYU-NAGE <I> :
In the case that aite came at you, grabbing your left hand or fore-arm with his right hand, make your hara move to in front of the grasped hand and while you are doing that, advance your left leg to aite‘s flank, and at the same time transform the orientation of your body by swiveling your koshi through 180 degrees.
Continue looking in precisely the same direction as aite, and having unbalanced him by raising both fore-arms, placing your left elbow and arm on aite‘s neck, and while shifting your center of gravity to your left leg, swivel your koshi to execute a throw that feels like brushing off, or sweeping away 1)
1) or “that feels like a sideways cut”
– – – Takemusu Aikido vol. 4, p.44