its not a problem
i am using my german centurion card all the time in japan and china.
you can pay at any JR station , you can pay at any lawson .
supermarkets, bigcamera etc. no problem!
getting cash is possible in tokyo at citibank and the deutschebank with amex or a maestro card.
all other banks do not give money on creditcards.
you can get cash with your visa at any post office!
dp