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To transfer your bitcoins to the exchanges is the same as transferring cash to your stockbrokers. Are you sure the bitcoin exchanges are regulated? Are you sure they are not crooks. If you have the coins in the regulated Japanese exchanges, then you are safer.
Yes do that indeed, Japan has not become famous enough from Mt. Gox.
Is not 2013 light years away for your beloved BTC time scale? Mt Gox

Ha Ha Ha. Do you want to put your money into Lehman Brothers?
The japanese exchanges are now fully legalized through parliament - the only one in the world. Why is this not the best?