This is the pocket wifi I used on my Japan trip. It is from Changi Recommends and it was an essential part of my trip. It cost me $8 a day (discounted) and it was usable the moment I landed in Tokyo. I got 4G speeds most of the time (except in the mountains) and a generous fair use limit of 1GB a day. Some days, I would even use this rather that a hotel's slower wifi.
The pocket router battery lasts pretty much the whole day. In my nine days away, I only had to charge it once but that was a day we were out from 5.30a.m. till midnight.
I used to have my own pocket router but the hassle with that is that I had to hunt for a local SIM card when I landed and that isn't always practical depending on the time you landed and the city. Not every country has easy access to prepaid local SIM cards with decently-priced data.
Using my own iPhone to hotspot drains my phone's battery, so I don't use that method.
Another method I used to get internet for Japanese Internet was to book a pocket wifi from an Japanese online service. But that method meant having to pick up the device at the post office at the Japanese airport, which was a problem if you do not reach Japan during their post office opening hours.
The Changi Recommends booths are open at the Singapore side 24 hours a day, so you can pick up and drop off your device regardless of your flight time.
With the Changi Recommends pocket wifi, I can share the data over wifi with more than one device so my iPhone, MacBook and my son's iPod Touch could all access the Internet. Heck, I'd get it even if I was traveling alone, I think.
Booking one is simple. I called the hotline a few days before my departure and gave them all my details. Then on the day of my flight, I went to their counter at the T3 arrival hall (they have a counter at every Changi terminal) and picked up the device. It comes in a black pouch with the charging cable and universal travel plug.
I added the wifi SSID and password printed on the back of the device to my iPhone and I was ready to use it when I landed.
Charges begin one day after you depart, which I think is very fair since you may be flying to a faraway land that takes 18-24 hours and won't be using it in the air.
When you return, just drop it off at the Changi Recommends counter and they bill you right there. It cannot be simpler.
The data service is reliable and stable and they cover quite a lot of countries, like the States, Japan, South-East Asia, and Europe. This is me using the service in my recent September San Francisco-Portland-Seattle-Yosemite trip.
The Europe one is interesting. Their pocket wifi works across many European countries so if you are doing an EU trip that crosses different European cities, you don't need to buy and change SIM cards like we did on our last European trip.
I tell you, this thing is a lifesaver. When you land, and you need to get online to use Google Maps to find your hotel or Airbnb, the pocket wifi is ready to go. I'm a fan already.