When you visit Japan, you can use your VISA, MASTER CARD and AMEX like you do back home with exception of ... people may ask you following question.
"Do you want to pay it at once?"
What is that mean? Why do they ask that question?
Well, unlike credit cards in the US, Japanese credit cards require you to pay 100% every month except you ask your merchant to charge it over period of months. いっかつ means, you pay full amount at the end of the month.
Since you are from other countries, this does not apply to any of you. But this is something you should know about it.