Something I didn't see anyone mention is the use of credit cards in Japan.
I could be wrong, but on our first trip we learned the hard way that they're just not used like they are in America. At home, we rarely carry cash and stupidly assumed it wouldn't be an issue in Japan. Now, we know not to rely on them at all!
If that has changed in the past 8 years, I haven't noticed because we're still carrying cash.
Best be prepared.