Credit cards are only good for purchases in some stores. In general, Sumitomo Banks will accept US credit cards for cash. Click here for VISA ATMs in Japan that take foreign credit cards for cash advance locator . Dairy products other than milk and yogurt are few. There are some bland cheeses to suit the Japanese taste.
Fresh fruits are expensive.
Come with an open mind and eat what the Japanese eat. There are KFCs and MacDonalds in most major cities when you can't adapt. Check out the Tokyo Cuisine Link . Average restaurant cost of breakfast 500 yen, lunch 800 yen, dinner 800 - 1,500 yen. Everyone takes care of their own meals on the 2-week rail trip.