The long post is inserted into the body.
making sure that the flat of the neck lines up with the membrane.
The parts of the neck slight straigh together.
The head then just fits into the end of the neck.
If your kokyu has a damaged or missing membrane, I'm afraid I have no idea on how to replace it, other than it is glued on. There are videos on replacing membranes on shamisen and sanshin which would probably be a very simular process. I would stongly recommend an artifical skin if you are reheading. Some say they don't sound as nice, but they're cheaper, easier to obtain in North America and ethically unquestionable.
