Use of Credit Cards in Japan

Credit Cards like American Express, Visa, Diners Club, and MasterCard are usually accepted at major facilities (hotels, large stores, restaurants), but it may not be accepted at smaller shops and discount stores. Japan is still mostly a cash country and that means that even a big city in some shops the procedure of payment using a credit card (even one issued in Japan) will be much longer that paying in cash, just be tolerant.
Other shops, which have point cards (gives a discount on every buy + you can use the points for your next time you visit the shop), may not accept a credit card if you would like to use the point card, or may not give points for your buy if you pay for it using a credit card.

If you travel not to a major cities you should have enough cash, because there you card will probably not be accepted.