If you want physical, ordering from CDJapan (linked in the home post) lets you ship internationally very easily. It’s what I use for physical orders; however, one book is usually not worth shipping, so I rarely buy physical unless I’m ordering in bulk.
If you want to order from Amazon, you do have to have a Japanese account regardless of it is digital or physical, and you do have to have a Japanese address listed, either by putting a nonsense one, or by using a forwarding service like Tenso (which only charges you when you actually ship using it, but just having an address with it is free, as I recently was told).
Regardless, if you have the JP address as the primary one on the account, you can then add a secondary address for your actual address and ship directly there from Amazon (at least, this is the case in the US and Canada. Not sure about elsewhere).
Other digital options if you don’t want to use Amazon is just to use Bookwalker (also linked in the home post). You can change the language for Bookwalker to English (but still shop JP manga) if you don’t feel comfortable shoppinb in Japanese yet, but either way, it’s also quite simple. Just create an account, buy, and download. Pretty sure they have their own app, as well, but you can also read directly in browser, if you prefer.
I have a Kindle that I have specifically for Japanese, so I prefer the Amazon route (even if I cringe at putting more money in their pocket, the convenience is undeniable), persoanlly, but Bookwalker is probably more immediately user-friendly if you don’t want to set up what you need to for Amazon (a specific device that only uses your JP login for Kindle, the address, separate account from your existing Amazon account, etc).