The site mentions on its Japanese FAQ that they don't do overseas shipping, which isn't particularly surprising given the logistics involved in doing foreign shipments from Japan, as well as they fact that they sell Japanese games made by both Konami and other companies, which aren't "supposed" to be exported outside of the country. You can get around all of this by setting up a Tenso account, which enables you to have a free Japanese PO box that will automatically have anything shipped to it forwarded to your actual address. Of course, that means you have to pay Tenso an additional shipping and handling fee in addition to the cost of having it shipped within Japan and, if my memory is correct, they only do EMS shipping since, not only is it the fastest international shipping option available out of Japan, but I believe the only one they can do that comes with tracking numbers. I used them back when I lived in the States and everything worked out just fine and the people running their customer support are nice and helpful. I haven't used them in years, especially now that I've been living in Japan, but as far as I know, they continue to be well-regarded.
Of course, the thing about using Tenso is that you have to fill out the Japanese order forms on the site you're purchasing from on your own. I think they include all of the necessary Japanese terms with your address so you can match up the information correctly on the order form, but again, I haven't had a need to use my own account in quite some time. Worst comes to worst, Google Translate should be competent enough at this point to handle order form translations okay. If you go through with it and still come out in a rut, I'd be willing assist you in translating stuff manually.
If that all sounds like a hassle, though, I know Play-Asia is known to stock some things from Konamistyle on their site. I don't know how regularly they get new things and they usually just get the high-end game bundles, so I don't know if they'd have anything you want, but that's also a potential option and certainly a more straightforward one than Tenso
