I just got back from Japan. Great place and I'd be happy to add it back into my travel rotations!
Misc observations:
For "wifi" you need access to internet to get it. Many wifi you need to use your email to activate access to the wifi. So definitely consider acquiring a SIM card. Google maps cannot use offline mode in Japan, and is unreliable, but still the best option on hand.
I hit Tokyo, Kyoto, Hiroshima/Miyajima, Shin-Kobe and Shin-Osaka in 10 ish days. Not exhaustively hit all locations, but the major points.
In Kyoto, definitely consider a bus day pass. A metro day pass is 600 in Kyoto, a day pass in Tokyo is 1200 yen I believe.
Japan with wifi is probably both the easiest and most difficult place to navigate I have ever visited. If you mess up (and you will) there are so many alternative methods to get to your location, it's easy to fix. But there's also so many moving parts, it's easy to mess up going there in the first place.
Definitely add extra time getting through airport security and customs in Japan when departing. I put aside 2 hours and barely squeaked in with 10 extra minutes to spare.
Robot cafe. Nothing online does it justice. It's pure sensory overload. It's like a combination of Mad Max fury road and Pacific Rim fights but Japan B movie style. So stupid! So awesome!
Coins, you will have many. Make sure you have a wallet that can keep coins.
Make a list of items to do in an area for back up if certain spots don't work out. I ran into a few holiday closures I did not expect. It didn't mess up too much of my trip by having a back up place to visit on hand.
Food... so freaking good.
Walking. So much walking. If I had to venture a guess, my wife and I were easily doing 10-30 km a day. You'll walk as travel, walk in parks, walk in temples/shrines. From the moment you wake to the end of the day, you will spend a ridiculous amount of time on your feet. Invest in a good set of shoes and heel slips.
The JR pass' unlimited travel can be ridiculously abused. Consider using it to its maximum.
Shopping. I don't know why, but I barely shopped. I spent all my money on experiences and food. I expected to shop, but I'm not sure if it's the exchange rate or whatever, but nothing felt like an amazing deal. Lots of good ones for sure, but nothing great. I just acquired things that I knew I couldn't acquire in Canada.