JR pass - is an inexpensive way for tourists to travel around Japan by rail. You need to order it before coming to Japan, as it’s not available for sale in the country. We used it extensively and I can’t imagine traveling without it. This is a good article on how to get it.
Revolut - it’s a prepaid travel card that gives you interbank rate exchange. Interbank means that the rates are the same as banks give each other. To sign up, you need to download the app and fill up a few details and then request the master card assigned to your account (I had to wait about 10 days to get one). It’s easy to top up, transactions almost instantly appears on the phone, the rates are good. Every transaction I made was with the same avg rate as google showed me. And it’s free, or at leas it was at the time of writing.
wifi router - Internet access has become one of the primal needs these days, so to avoid the anxiety of not having it in Japan the best option is to rent a wifi router. There are many companies that offers it. You need to select days you are in Japan, where you want it to be delivered (airport or hotel) and that’s it. I’ve used wifibuddy, and I was mostly satisfied with the connection.