Japan is mostly cash-based for face-to-face transactions.
Online, users are extremely comfortable paying electronically. You have to remember that paying via mobile was a thing here several years before the rest of the world, so people have had longer to acclimatize.
As a reference point, Japan spent around $8B via mobile phones in 2006 (i.e. before the iphone launched).
They may well have done for legal reasons, but the point for consumers was that you could find a product in a web page and hit purchase, and the cost would just show up as a line item in your phone bill, without any signups or credit card numbers.
Similar deal with NFC payments. They launched here in 2004, and were fairly widespread by the time smartphones arrived. It used to be very common for people to move "up" to a smartphone and then be surprised to find out how many features they'd given up.
Don't they also have a system similar to the French "net pay" (or whatever the name) where you can pay and have it billed on your next carrier bill? Here even Google play supports it, and while not the major payment system it does remove all friction from online payment.
Online, users are extremely comfortable paying electronically. You have to remember that paying via mobile was a thing here several years before the rest of the world, so people have had longer to acclimatize.
As a reference point, Japan spent around $8B via mobile phones in 2006 (i.e. before the iphone launched).