It's PayPay country now.

https://paypay.ne.jp

You can go to some of the most remote places and they'll accept paypay lol

Most places accept IC cards, which work like debit cards that you load money onto. Hotels support credit cards, but some western banks have trouble with the Japanese payment system.

Since 2003 JCB has had an agreement to process Amex transactions in Japan, so Amex is accepted everywhere that credit cards are accepted, which is usually uncommon.

Coincidentally, that’s also the most "Amex in Europe" experience ever

As mentioned by others, things have changed - I used credit card 90% of the time on my last trip earlier this year.

it's changed pretty drastically in the past 10 years. aside from a few odd tiny bars, i think cards were accepted everywhere i went in tokyo and kyoto

Not anymore