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Almost every eSIM problem travellers hit in Japan comes from doing the right steps in the wrong order. The profile has to be installed while you still have internet, and it has to stay switched off until you land. Get that sequence right and the rest is four toggles.
The sequence
- At home, on wi-fi: buy the plan and install the profile. Do not activate it.
- Label it something obvious. You will be picking it out of a list later.
- On landing: turn the line on, set it as your data line, and switch data roaming on for it.
- Turn data off on your home SIM so it cannot quietly bill you.
- Data-only plans give you no Japanese number, which matters for emergency calls.
Before you buy
Two hardware conditions, both non-negotiable: the phone supports eSIM, and it is not locked to your home carrier. Both are checked in minutes and neither can be fixed at the airport. See the four phone checks first.
Also decide whether an eSIM is the right choice at all. Travelling as a group, or with a locked phone, points to pocket wi-fi instead — the arbitration table compares the three options on price per gigabyte and on the practical trade-offs.
Install at home, on wi-fi
This is the step people skip and regret. Installing an eSIM profile downloads it from the provider’s server, which requires a working internet connection. The moment you need the eSIM is the moment you do not have one. So install it days before you fly.
- Scan the QR code the provider emails you, or install through their app. Both do the same thing.
- Give the line a name you will recognise when tired. “Japan data” beats whatever the provider calls itself.
- Keep the QR code. Most can only be installed once, but if the install fails halfway you will want it.
- Leave the line turned off until you land. Many plans start counting validity from first connection to a network, not from purchase.
Check when your validity clock starts
Providers differ. Some start the day count at purchase, some at first network connection, some at a date you choose. A seven-day plan bought a week early and started on the wrong trigger expires the day you arrive. Read that line on the product page before paying.
On landing: four settings
Do this at the gate or in the immigration queue, not on the train. The exact menu names differ between iOS and Android, but the four things you are changing are the same.
| Setting | Set it to |
|---|---|
| The Japan line | On |
| Mobile data / default data line | The Japan line |
| Data roaming, on the Japan line | On — yes, really |
| Mobile data on your home line | Off |
The third one stops everybody. Turning on data roaming sounds like the setting that generates a four-figure bill, and on your home SIM it is. On the travel eSIM it is required: these plans work by roaming onto a Japanese network, so with roaming off the line connects to nothing. It cannot cost you anything, because the plan is prepaid and has no billing relationship with your home carrier.
Leave your home SIM enabled for calls and texts if you want to keep receiving bank verification codes. Just make sure its data is off. That combination is the real reason dual-SIM phones are worth having on a trip.
When it says no service
Work down this list in order. It is almost always one of the first three.
- Data roaming is off. Check it on the eSIM line specifically, not the phone as a whole. This is most of the cases.
- The wrong line is set as the data line. The eSIM can be on and connected and still not be the one carrying your traffic.
- Aeroplane mode never came off, or came off before you left the aircraft and the phone is still holding a stale state. Toggle it on and off again.
- Restart the phone. Unglamorous and it works more often than it should.
- Select the network manually. In network settings, turn off automatic selection and pick the Japanese operator your provider names. Useful when the phone latches onto a network your plan does not cover.
- Check the APN if the provider published one. Most modern eSIMs configure it themselves; a few still want it typed in.
Coverage is not the problem
Japanese network coverage is dense, including on most Shinkansen routes and in subway tunnels. If you have no signal in central Tokyo, it is a settings problem on your phone, not a gap in the network. Deep rural mountain areas are the genuine exception.
What a data-only plan cannot do
Most travel eSIMs sold for Japan are data-only. You get internet and no Japanese phone number, which has consequences worth knowing before you rely on one.
- No conventional voice calls, so no calling a restaurant to hold a table, and no calling 110 or 119 from that line. This is the one that matters — see how emergency calls work in Japan.
- No Japanese SMS, which blocks the sign-up flow for some Japanese services that verify by text.
- Some restaurant and ticket booking sites require a domestic number in the form. A hotel will often let you use theirs.
Messaging and internet calling work normally over data, and in practice Japan runs on messaging apps rather than phone calls anyway. The gap is specifically emergency services and domestic verification.
Before you fly home
- Turn your home data back on before you land, or you will spend the arrival wondering why nothing loads.
- Set the data line back to your home SIM.
- Delete the Japan profile only once you are sure you are not returning within its validity. Deleting is usually permanent, and reinstalling from the same QR code often is not possible.
Sources
- GSMA — eSIM remote SIM provisioning specification and device requirements.
- Ministry of Internal Affairs and Communications — allocated mobile frequency bands for Japanese operators.
- Apple and Google published documentation on adding, labelling and removing eSIM profiles and on setting the default data line.
Data checked: 2026-09-27
