I have the same problem. You can get access to iTunes Japan by clicking on the My Store button at the bottom of the iTunes store. That will take you to the iTunes store in Japan (which will display everything in Japanese, of course). However, you will not be able to purchase anything from the Japanese iTunes store. This is because of copyright issues. I found out through the iTunes help pages, that the only way to get an account is to have a physical address in Japan to list as your mailing address. On top of that, the iTunes card must physically be bought in Japan.
There is a possible way around that, but you have to be exceedingly patient: you can request the song/album/artist to be added to the iTunes store by going to the Request Music web page. Of course, there is no guarantee as to when or even if it will be added. If you get several friends to also request it along with you, then The Powers That Be just might add it!
My daughter loves Mr. Feather by Ellegarden, but it's not available yet. So, I put in a request for it for her.
Of course, if you don't mind buying the whole CD, there's always good old www.amazon.com for starters...