But I'm telling you from my experience. I ordered many things just even with Sony. I even got PS5 shipped here from amznjpn but yeah, use what works best for you.
This does not apply to the PS5, never said that. Nor does it apply to the Z7M2, XBA-Z5, XBA-N1/N3, nor ZX507. It applies to WM1 Series DAP and Z1R Earphone/Headphone.
And this is not uncommon, a lot of companies do that. The cotsubu TWS from Final are also sold only in Japan, like the FitEar TG335. If you choose international shipping, more than 9/10 of all articles disappear. It is common and normal on amazon.co.jp that only a few selected items are applicable for international shipping. It os not bad luck, thats just how things work in japan.
You can not recommend to people to hope/wait for legal holes due to mistakes/errors. That is my point. If that works for you because you have luck, thats fine for you, but some people may follow your lead.
But there are important limitations to this, depending on the country, there is no way to send it back, neither in case of damage, nor in case of refund if you don't like it. Because you was never supposed to get it they might just block you from sending it back.
In Germany, for example, private persons are not allowed to send any item containing an Li-Ion Battery to Japan. If you used an forwarding service, they will take care about that. But if you bought an article that you was never supposed to get in the first place, (like i had once with an Xperia Z4), they will just not accept your shipping. You will get an shipping label from amazon and DHL will tell you, they will not accept your package.
So if there is an technical defect, there might be no way to send it in for repair depending on the law of your country and other aspects. That is an important thing to know.
There is an official and legal way to buy these from Japan and that is using an forwarding service. Some stores like e-earphone even work with them together to provide international shipment.
So if anyone is interested in getting an WM1 Walkman from Japan, use a forwarding service like Tenso. Otherwise you might be blocked out from sending them back in case of any issues.