just carry cash ba...
alot of japanese do that
So far based on experience best bet is to use Citibank atm card to withdraw cash. Not that the rates is fantastic, but sure can use as long as you use Citibank atm machines. Longtime ago when I first started going Japan you can easily use POSB or DBS atm card in many of Japan's atm machines, especially those in 7-11 or family marts, but that seems to stop a few years back when I tried.
For credit cards, best rate IMO is to use the UOB JCB card, rates are much better, and makes a difference esp when you use for big ticket items.
And of course, cash is king, anywhere you go