Please note that this stream may contain spoilers for Kingdom Hearts III.
You need a Japanese Sony account, Japanese form of transactional currency, and a Japanese address. You do get a 10% new member discount if you can somehow fulfill those requirements, though! As others have mentioned, proxy service is probably the cleanest way if you're not in Nippon. Otherwise you can try retailers like "nin-nin-game" who have both the Walkman and headphones up for sale (take their terrible reviews with a grain of salt, I got my JP KH3 PS4 Pro from them fwiw).
I actually very much like the composition of the article. It's perfectly informative without being long-winded, and links to every source you cite. I say keep it up!
I have all of the keyblade keychains they've made so far, including the limited red version of Lea's which I bought in Akihabara recently. Is the plush the same one from the DDD special edition?