Exercise for learning the kyudo tenouchi.

Try this exercise to learn the tenouchi (proper gripping of the weapon) principles and experience the feeling of yugaeri (bow turning after the release):
1 - set the left hand's tenmonsen (hearth line) on the left-front corner of the bow.
2 - bring together the small, ring and middle fingers. DON'T SQUEEZE THE NIGIRI.
3 - fold the skin flap between your thumb and index down (that area is called the kokou - tiger's mouth - 虎口).
4 - push the yumi's right rear corner with the base of your thumb, straigth towards front.
5 - pull the string not more than 2cm. Hold it very loosely between the right hand's fingers, so that it releases naturally after this very short pull. You should also have the feeling that you're pushing the string and causing a release with your left hand's thumb.
The tenmonsen forms a fulcrum and the thumb pushing on the nigiri corner is torquing the yumi. Thus the yumi will rotate about 270 degrees in hand, if not held tightly.
This should allow the left hand to learn how to be tight enough for the correct tsunomi (force on the grip) to be applied, while being relaxed enough to allow the yumi not to be choked and to rotate the correct amount after the hanare (release).