Many Japanese artists have few or even none of their releases available outside of the Japanese iTunes store. As the store requires both a Japanese credit card and a Japanese address, buying from there sounds impossible, but it can be done.
First, we get around the problem of needing a Japanese credit card by using iTunes Japan gift cards instead. There are several sites that offer gift card codes, I went for japan-codes.com as they had good reviews and allowed payment in GBP via Paypal (avoiding Paypal charging a currency conversion fee, or my card charging an overseas transaction fee).
I bought the ¥5000 card, and after receiving an e-mail confirmation, the code arrived in only a few minutes. Rather than the code being in the e-mail itself, they e-mailed a link to a scan of the gift card.
The next step is setting up an account on the iTunes Japan store. If you have an account with another iTunes store, you’ll have to use a different e-mail address for iTunes Japan, as each e-mail can only be attached be one iTunes account. Sign out of your existing iTunes account, scroll to the bottom of the page and click the flag in the bottom right corner, then select Japan from the list of countries. The store used to be in Japanese, but is now displayed in the language your iTunes was registered in.
When setting up an account, iTunes Japan will ask for a payment option. To make the ‘none’ option (i.e. using gift cards) appear, select a free item and click the ‘get’ button. As it’s a free item, it will let you select ‘none’ and you’ll be able to set up an account. Don’t worry if ‘none’ doesn’t appear, this problem happens to Japanese users as well, just return to the homepage and try again. I had to try it a few times, but it eventually appeared!
Now that you have an account, you can redeem your gift card and start buying! Select ‘redeem’ from the Music Quick Links menu a the side, and type in your code
The buying process itself is as the same as with any other iTunes store – account credit is displayed in the top right, and to buy you just click the ‘buy’ button underneath the album cover if you want the whole album/single, or the ‘buy’ button next to a song if you only want to buy one song.
iTunes doesn’t set up a separate library for purchases from different stores, so your music will all be together.
Some people have said they’ve not been unable to move between accounts with different stores when they have remaining credit, but as you can see below, I haven’t had this issue.