1. Start by Checking These Five Things
Here’s the short answer.
If your eSIM is already installed but not working in Japan,
start by checking the five points below.
These are the most common causes, shared by roughly 80% of cases where travelers feel that
“my eSIM doesn’t work in Japan.”
Rather than assuming something complicated is wrong,
check the items that seem most likely to apply to your situation.
- Delete the eSIM profile once, then reinstall it
- Review your mobile data and data roaming settings
- Check whether a carrier settings update is available
- Switch network selection from Automatic to Manual
- Confirm the APN (Access Point Name) settings
In this article, I’ll explain why these fixes work,
and which one to focus on depending on your symptoms, step by step.
2. Common Causes Behind eSIM Issues in Japan
In most cases, eSIM problems in Japan are not caused by device failure or network outages.
They usually come down to misaligned settings or synchronization issues.
Below are the most common causes.
Profile Synchronization Issues
An eSIM profile contains a full set of settings that define how this device is allowed to connect and under what conditions.
If the profile information on your phone and the information held by the eSIM provider’s server are not properly synchronized,
the eSIM may appear installed but fail to connect.
This mismatch is more common than it sounds.
Data Roaming Is Turned Off
Many eSIMs used in Japan require data roaming to be enabled in order to work.
You may associate roaming with high charges, but with eSIMs, the situation is different.
In most cases, data roaming must be turned on for the connection to function at all.
Outdated Carrier Settings
Carrier settings are internal configurations that control how your device communicates with a carrier’s network.
If these settings are outdated, your phone may fail to connect properly—even when the eSIM itself is valid.
This issue tends to appear:
- right after arrival in Japan
- or shortly after an OS update
Automatic Network Selection Fails
With overseas eSIMs, it’s possible to see signal bars but still have no data connection.
In these cases, the device may have automatically selected a network that isn’t suitable for data communication in Japan.
In other words, the phone is connected—but not to the right network.
APN Is Missing or Incorrect
Depending on your OS, device, and eSIM profile,
you may need to manually configure the APN (Access Point Name).
If the APN is missing or incorrect,
data communication will not start—even if signal bars are visible.
In the next section, we’ll look at where to check and what to change for each of these causes, one by one.
3. Fixes That Work in Each Case
From here, we’ll look at where to check and what to change, based on the causes outlined in Section 2.
You don’t need to try everything in order.
Start with the fix that best matches your situation.
3-1. Reinstall the eSIM Profile
This is effective if:
- The eSIM shows as “installed,” but data never starts working
- It worked yesterday but suddenly stopped
In these cases, the profile information on your device and the provider’s server may be out of sync.
What to do
- Delete the eSIM profile from your device
- Download the eSIM again
- Reinstall it
This forces the eSIM’s settings and authentication data to resynchronize from scratch.
Notes
- Reinstallation requires a stable Wi-Fi connection
- With QR-code–based eSIMs, you may need to re-obtain the QR code or installation link
- Some eSIMs cannot be restored once deleted, so it’s best to check the provider’s instructions in advance
3-2. Check Mobile Data and Data Roaming Settings
This is effective if:
- You see signal bars, but data does not work
- You haven’t touched any settings since arriving in Japan
Many overseas eSIMs will not work unless data roaming is turned on.
You may associate roaming with unexpected charges, but with eSIMs, usage is controlled by your plan.
Turning roaming on does not itself trigger extra fees.
What to check
- Make sure mobile data is assigned to the eSIM (not your physical SIM)
- Confirm that data roaming is turned on
If either of these is off, data will not start—no matter what else you fix.
3-3. Check for a Carrier Settings Update
This is effective if:
- Your OS is up to date, but data still doesn’t work
- You just arrived in Japan, or just updated your OS
- You recently added the eSIM
Carrier settings are internal network configuration rules delivered separately from OS updates.
If these settings are outdated, your phone may fail to communicate properly with Japanese networks.
Key points
- Carrier settings updates are not always applied automatically
- Checking while connected to Wi-Fi tends to work best
In some cases, simply applying the update makes data start working again—without changing anything else.
3-4. Manually Select the Network
This is effective if:
- Signal strength looks fine, but mobile data does not work
Overseas eSIMs are usually configured in advance to use specific Japanese networks
(for example, only a NTT Docomo–based network).
However, your phone may automatically choose a network based solely on signal strength and end up connecting to one your eSIM isn’t intended to use.
When that happens, data may not start—even though you appear connected.
Manually selecting the network can resolve this.
How to think about manual selection
You will typically see networks corresponding to one of these groups:
- Docomo-based
- au-based
- SoftBank-based
Which one you should choose depends on which network your eSIM is designed to use.
This information is usually listed in the provider’s setup email or support documentation.
If multiple options appear, simply selecting the one that actually allows data to start is enough.
3-5. Check and Optimize the APN (Access Point Name)
This is effective if:
- All other settings look correct
- Data still does not work
- You’re using an Android device or a specific eSIM type
The APN is the entry point that allows data communication to begin.
Depending on the eSIM profile, the APN may not be set automatically and may require manual input.
What to check
- Make sure the APN field is not empty
- Confirm that the values match the provider’s instructions
If the APN is missing or incorrect, data will not start—even if signal bars are visible.
In most cases, checking these five points is enough to get an eSIM working in Japan.
If your connection still doesn’t start after that, the issue is likely not a simple settings problem.
At that point, continuing to tweak options may not be the most effective use of your time.
In some situations, it can be faster and less stressful to switch to an alternative way of staying connected, rather than trying to force a setup that isn’t designed to work.
4. Why eSIM Issues Are So Common in Japan
After going through the fixes above, you may still feel that setting up an eSIM in Japan is oddly complicated.
That impression isn’t wrong.
The difficulty comes from the structure of Japan’s mobile network itself, which is not particularly transparent for travelers.
Rather than listing more steps, this section explains why these problems happen in the first place.
4-1. Why “Connected to Wi-Fi” Doesn’t Mean You’re Safe
When you’re connected to free Wi-Fi at a hotel or café, it’s easy to assume everything is working fine.
In reality, while Wi-Fi is active, your phone does not use mobile data at all—neither physical SIM nor eSIM.
As a result, any issues with your eSIM remain hidden.
This is why many travelers feel that “it was working a moment ago, but stopped outside.”
The problem doesn’t suddenly appear outdoors—it simply becomes visible the moment your eSIM is actually used for the first time.
4-2. Japan’s eSIM and MVNO Structure Is More Complex Than It Looks
Japan’s mobile network is built on a layered structure.
Major carriers provide the underlying infrastructure, MVNOs lease that infrastructure, and eSIM services are often offered on top of those MVNOs.
Because of this, connection rules—such as profile behavior, roaming requirements, and network selection—can vary slightly from one eSIM to another.
An eSIM that worked perfectly in other countries may behave differently in Japan for this reason.
4-3. Not All eSIMs Are Designed for Short-Term Travel
The term “eSIM” often gives the impression that all services are travel-friendly by default.
In practice, that isn’t always the case.
Some eSIMs are designed primarily for long-term use, or for specific regions or devices.
When used on a short trip, these services may technically work but behave unpredictably.
If stability matters during a short stay, it’s generally safer to choose services with a long track record among travelers.
For example, Airalo and Ubigi are widely used in Japan and are commonly reported to work reliably for short-term visitors.
4-4. Japan’s Network Characteristics Can Also Play a Role
Japan’s mobile networks operate across many frequency bands, and base stations are densely deployed in urban areas.
This makes it possible for a device to show a strong signal while still struggling with actual data transmission.
In such cases, the issue is less about incorrect settings and more about how the eSIM’s design interacts with the local network environment.
When an eSIM doesn’t work in Japan, the cause isn’t always a setting you missed.
Understanding the structure and assumptions behind the network can make it easier to see that the problem isn’t necessarily your fault.
And in some situations, choosing a communication method better suited to the environment is simply the more practical decision.
5. Frequently Asked Questions (FAQ)
This section covers the questions that travelers most commonly get stuck on when using an eSIM in Japan.
Q1. What’s the best way to use an eSIM together with a physical SIM?
The short answer is:
separating their roles causes the fewest problems.
In most cases, the following setup works best:
- Physical SIM: calls and SMS (to keep your home number active)
- eSIM: mobile data only
Problems tend to occur when both the physical SIM and the eSIM are assigned to mobile data, or when the phone unexpectedly uses the physical SIM for data instead.
If you’re using an eSIM in Japan, always make sure that mobile data is set to use the eSIM.
If this is wrong, data may not work even if every other setting looks correct.
Q2. The APN field doesn’t appear. Is something wrong?
Not necessarily.
With some eSIMs, the APN (Access Point Name) is built directly into the profile, and the manual APN settings screen doesn’t appear at all.
In those cases,
no visible APN = automatically configured,
which is usually normal.
That said, on some Android devices or with certain eSIMs, data won’t start unless the APN is entered manually.
If you’re unsure which applies to your case, check whether your eSIM provider’s instructions mention manual APN setup.
Q3. Does eSIM behavior differ between iPhone and Android?
Yes—there are differences in the details.
On iPhone, eSIM setup and profile management are tightly controlled by the OS, and in many cases it’s designed to “just work” once installed.
On Android, behavior varies more depending on the device manufacturer and OS version.
Manual APN configuration or different network selection behavior is more common.
This doesn’t mean one platform is better than the other.
Android simply offers more room for adjustment, which also means there are more chances to get stuck in settings.
Q4. Is it okay to set everything up after arriving in Japan?
In most cases, yes.
However, this assumes you have access to a Wi-Fi connection.
Troubleshooting steps such as reinstalling an eSIM or applying carrier settings updates often require Wi-Fi.
For that reason, it’s best to confirm that everything works while you’re at the airport or hotel, where stable Wi-Fi is available.
As for when to activate your eSIM, this depends on the provider.
Broadly speaking, eSIMs fall into two categories:
- Those where the validity period starts when the eSIM is installed
- Those where it starts when data is first used
Because of this, whether it’s safe to activate an eSIM before arriving in Japan depends entirely on the provider’s policy.
If you’re unsure, activating it after arrival—using stable Wi-Fi at the airport or hotel—is the safest option.
This helps avoid accidentally consuming your usage period before you actually need it.
Q5. If I’m still worried, what should I do?
The most reliable approach is to have one backup option ready.
Common alternatives include:
- A pocket Wi-Fi device
- A physical SIM card
eSIMs are convenient, but if you want truly stress-free travel, it’s best not to rely on a single communication method for everything.
6. Summary: How to Think and What to Do When Your eSIM Doesn’t Work
If your eSIM isn’t working in Japan, take a moment and calmly check the following five points.
The 5 Things to Check First (Quick Review)
- Delete the eSIM profile once, then reinstall it
- Make sure mobile data is assigned to the eSIM
- Confirm that data roaming is turned ON
- Check whether a carrier settings update is available
- Try selecting the network manually instead of automatic
In most cases, these five steps are enough to resolve common eSIM issues in Japan.
However, if you’re still unsure, it can sometimes be faster not to deal with everything on your own.
- Airport mobile counters
- Carrier shops
- Locations with on-site support staff
In these environments, staff may be able to quickly determine whether the issue is related to your device, the eSIM’s specifications, or an incompatible combination that simply won’t work.
Final Checklist for Travelers
Before departure or after arrival, it helps to confirm just these points:
- You tested the eSIM while connected to stable Wi-Fi
- Mobile data is set to the eSIM
- You understand whether your eSIM requires roaming to be ON
With that, you’re ready to leave connectivity worries behind and focus on enjoying your trip.
If you want a clear, practical overview of eSIMs, physical SIM cards, and pocket Wi-Fi—and how to choose the right option for your travel style in Japan—see this guide:
→ How to Stay Connected in Japan: A Practical Guide That Actually Works
