your credit cards are useless in Japan.

You may have to resort to getting a cash advance on your card at the airport before you board the plane....just accept the extra credit charges as experience and maybe let a fellow traveller know of your experience.

Japan is expensive, (understatement) you should never travel there with less than USA$10,000. Never count on being able to use a credit card in a foreign country. I have travelled to many countries and was surprised at how useless they were.