You can use it with Amazon.jp but most of the time Amazon ships directly to everywhere,
no proxy needed
In fact you can use it with any japanese store that has a link to a product, the inquiry is free itself and Buyee reports back if they can buy it for you or not
Amazon.jp does ship everywhere, but their international items use a separate warehouse, and sometimes items are only stocked in the domestic one(s) and are unavailable for international shipping.
You can get a proxy shipping address via Tenso (different service but iirc same company as Buyee) and then have stuff shipped there from Amazon.jp & consolidated and shipped to you.
I used it successfully for all the cheap and/or rare second hand books available on Japanese Amazons that Amazon will normally not ship internationaly (as its actually a miriad of small sellers listing the via Amazon and often only shipping domestically).
You can use it with Amazon.jp but most of the time Amazon ships directly to everywhere, no proxy needed
In fact you can use it with any japanese store that has a link to a product, the inquiry is free itself and Buyee reports back if they can buy it for you or not
If you use Discord then the Buyee server is very helpful https://discord.com/invite/YRg3DgkBpS