Josua comments

Cashless only works if the infrastructure is capable of supporting it in the short-term: as in the kind where it only takes something like the flip of a switch or something like that.

Easiest way to do the first step for cashless is making the available cashless payments more broadly supported by major chains of stores and other businesses aside from those that have already done so.

Given Japan's culture of hard-cash usage, it should be noted that for cashless to be more broadly accepted and used, they need to make it easier for users to use both cash and cashless methods seamlessly.

i.e: You pay with cash, and get some benefit like some sort of point cashback or something like that for your e-payment, should you have one on your phone or something like that.

It won't be easy, but at least it should give people some ideas on how to integrate cashless payment into a hard-cash dominated society like Japan.