That's what I did, I bought the gift card directly through Amazon. I also made the new account and sent it a ¥1000 giftcard without adding any information to that account, but still no luck. It still asks me to add payment info that is "local" even though it has ¥1000 to spend instead and the account's shipping address is in Japan. I hadn't considered the VPN idea though. I'll try that next.
My "fake japanese address" is a mcdonalds in hokaido or something. It's not actually fake, it's just not actually mine.