[Sangetsu]

Cash is easy to carry, you shouldn't have to worry about getting robbed (unless you get very drunk in Roppongi). You'll probably find that your ATM card will not work in convenience store ATM machines, as well as many of the ATM machines in train stations and such. The only reliable ATM machines are at the post office.

Credit cards are widely accepted in Japan, but nowhere on the same scale as in America. A surprisingly large number of shops and restaurants will not accept them, neither will convenience stores, with the exception of Lawson.