First, it is considerably more expensive to send stuff overseas to America than it is the other way around. It doesn’t help that sea mail is no longer supported.
Second, “Everywhere Visa is accepted” is the exception, rather than the rule, at least in Nagasaki. Typically only major stores and chains accept foreign credit cards. Most people use cash for everything.
Third, if you’re studying abroad in Japan and you want to buy something off the internet, keep in mind the fact that Paypal does not allow a person to have a billing address in one country and a shipping address in another. This restriction applies when websites use Paypal simply for security reasons as well, so you don’t actually have to have an account to be shafted by this.
Fourth, identity theft happens. One of the other students here had her identity stolen a few weeks after arriving, and had a good sum charged on her card. She has since recovered the money. I have no idea as to the frequency of this, but it happened.
Fifth, it’s a pain in the rear to send money to/from Japan. If you can get the money in your bank account at home somehow, pulling it from an ATM is easy. Of course, there is typically some sort of bank fee plus a currency conversion fee. I’ve never withdrawn money from an ATM here; the fee was $5 per transaction in Canada. Wiring money is another option. It is quick, but it is also expensive (about $50). You have to have a Japanese bank account as well. It takes a little bit longer, but the easiest way to send money out of Japan would be with an international money order. However, they are expensive if you have to send a large amount of funds. They cost $20 each, with a limit of $700 per day. There is no fee on the receiving end, and they can be cashed at any U.S. post office. They can be denominated in foreign currency as well. Of course, this would also be a viable option for receiving money in Japan.