I was wondering if transferring a significant amount of money from my Japanese bank account to my Canadian bank account would ring some alarms somewhere. I already paid more than my share of taxes in Japan for that money so I wouldn't want Canada to come annoy me about taxes or something.
Most countries tax income, but not a transfer of already taxed money, so you have nothing to worry about.
You need to be prepared - if asked - to proof that the money was legally earned, and that you paid taxes for the income when you originally got it. Chances are small that anyone asks though, if you are not being investigated for other reasons already.