I might be on a different wave length but..
You mean to get the money offshore?
Actually it struck me that you could move a chunk of money without transferring it (at least all of it, I mean) through the banking systems. Imagine you have a margin forex account in Japan, and another margin forex account offshore, and you open offsetting positions on these accounts simultaneously... One goes up, the other goes down... using 25:1 leverage on both...
If it's your Japanese forex account that goes down in net value, to the NTA it'd look like you've actually suffered a loss (which might be a convenient thing depending on your intentions.)
There are issues with getting initial funds into the offshore account etc, but I'm thinking they're probably not insurmountable.
In this respect you are talking about accessing the funds, correct? I seem to recall people using bank cards issued by offshore banks for this purpose. Again, not speaking from experience though.
I just recently got interested in this after reading the "
日本脱出" book that came out recently, which basically encouraged readers to avoid taxes, if not attempt to evade them

I'm sure that author will get a nice audit sometime!