As much fun as it is to explore a city with a physical map, I prefer Google Maps.
I've used a few different companies over the past years, but https://www.econnectjapan.com/ is by far my favourite.
They'll either ship to an airport and you can pick it up there, or (my new preferred method) you can have it shipped to your hotel. You feel a little bit like Jason Bourne when you check in, and they hand you a package.
You'll need an unlocked phone. Buy an old unlocked iPhone 5 if you're locked to a carrier.
Here is a photograph of me riding a bike in Japan: