[Sangetsu]

You should forget about the Japan Post bank account. Open an account at Shinsei bank instead, and then open a Paypal Japan account (it's actually an English language site). Then link your American bank account to an American Paypal account. You can then transfer money back and forth between these accounts as necessary. The transaction fee is generally lower than what the post office charges for transfers, and is much cheaper than Western Union (which is no loner in Japan) or Moneygram.