Guide to mobile data in Japan
Once you’ve landed in Japan, getting mobile data will probably be your first priority: after all, you’ll need to pull up your navigation app to figure out how to get from the airport to your hotel! While you can wait until you’re there to sort out your mobile data, I’d recommend planning your mobile data solution before you leave for your trip.
There are three main solutions we’ll talk about here: pocket WiFi, eSIM, and physical SIM.
Pocket WiFi
Many people swear by the pocket WiFi devices, which can be cost effective. Essentially, a pocket WiFi device is a mobile router that you rent from a provider for the duration of your trip. You can connect all you and your travel partners’ devices to it, and they tend to be very cost effective. You can also book them prior to leaving for your trip. This might be the perfect solution for you, but I usually recommend against these devices for a few reasons:
It becomes yet another device you need to keep charged. Most of these pocket wifi devices were made years ago, and likely have much worse battery capacity than your phone.
It's one more item you need to carry with you at all times
It's a single point of failure for each device that relies upon it - better hope you don't misplace it, forget it at your hotel, or that it doesn't malfunction during your trip
It tethers everyone you're travelling with to one another. If you ever want to do separate things, all but one of you will need to go without data. I once saw a group of young adults get into a heated disagreement at Osaka's teamLab Botanical Garden exhibit because the person with the pocket wifi refused to hurry to the park entrance, and their waiting group couldn't access their tickets without data. They all ended up missing the entry time as a result.
eSIM
If your phone supports it, I would recommend an eSIM. I’ve used the Ubigi app on multiple trips (not just Japan) and it works flawlessly, isn't that expensive, and you can set it up prior to arriving. They offer a variety of data plans in various time intervals in case you need to top up at any point during your trip. You won't have a phone number, so you won't be able to use apps that require a local phone number like taxi apps or LINE, or make reservations via phone. You also won't be able to receive SMS-based MFA. That hasn't been a problem for me so far, though.
Physical SIM
The last option is to buy a physical SIM card at the airport. I did this on my first trip and it worked great, and the workers there were very helpful in setting it up. They also had a variety of data plans available. What I would not do is delay getting the SIM until you've entered the city, since workers at these cellular provider stores will be less likely to speak English and less likely to know about these visitor data plans.