There have been numerous past posts about the JCAB medical. You will need to use the search function - use of key words such as "JCAB", "Medical" and "Japan" should return meaningful results .
Searching the "Dunnunda / Godzone" and "Far East" forums should be sufficient.
The one comment I will make is that it is not for the faint hearted - amongst expat pilots it is rumoured to have an intial 75% failure rate.
Fark!