Dual SIM in Japan: Use Your eSIM and SIM at the Same Time
TL;DR
With dual SIM, you keep your home SIM card for calls and texts while using a PlanJapan eSIM for data in Japan. Setup takes 2 minutes: just assign the data line to your PlanJapan eSIM in your iPhone or Android settings, and disable roaming on your home SIM. Result: high-speed internet on the NTT Docomo network, without touching your regular plan.
What is dual SIM and why is it useful in Japan?
Dual SIM lets you use two phone lines simultaneously on a single device. In Japan, this means:
- Line 1 — your home SIM: keeps your number, receives your calls and texts (bank verification codes, messages from contacts)
- Line 2 — PlanJapan eSIM: handles all data connectivity (Maps, translation, social media, searches) on the NTT Docomo network
No need to remove your SIM card or juggle between two phones. Both lines coexist and work simultaneously.
Three possible dual SIM configurations
| Configuration | Description | Compatible devices |
|---|---|---|
| Nano-SIM + eSIM | Your physical home SIM + PlanJapan eSIM | iPhone XS to iPhone 14, Samsung Galaxy S21+, Pixel 3+ |
| eSIM + eSIM (dual eSIM) | Two simultaneous eSIMs (home + Japan) | iPhone 13+, iPhone 15+, Pixel 7+, Samsung Galaxy S24+ |
| Nano-SIM + nano-SIM | Two physical SIMs (no eSIM) | Some dual-SIM Androids — doesn't apply to eSIMs |
For most travelers, the nano-SIM (home) + eSIM (PlanJapan) configuration is the most common and simplest.
Why keep your home SIM active in Japan?
You might wonder: why not just switch everything to the PlanJapan eSIM? Here are the practical reasons to keep your home SIM:
- Receive verification texts: your bank, PayPal, or two-factor authentication services send codes to your home number
- Stay reachable by phone: family, emergencies, employer — your usual number stays active
- WhatsApp and iMessage: these apps are linked to your home number, they continue working normally via PlanJapan eSIM data
Setting up dual SIM on iPhone (step by step)
On iPhone, dual SIM management is done entirely from Settings. Here's the procedure once your PlanJapan eSIM is installed:
Step 1 — Name your lines
After installing the eSIM, iOS asks you to name each line. We recommend:
- Primary or Personal → your home SIM
- Travel or Japan → PlanJapan eSIM
These names help you quickly identify each line in menus.
Step 2 — Set the default data line
- Go to Settings → Cellular
- Tap "Cellular Data" (the first submenu)
- Select your PlanJapan eSIM (Travel / Japan)
This is the most important step: it tells the iPhone to use the PlanJapan eSIM for all internet browsing (Maps, Safari, Instagram, YouTube, etc.).
Step 3 — Set the default voice line
- Still in Settings → Cellular
- Tap "Default Voice Line"
- Select your home SIM (Primary / Personal)
This way, all your outgoing calls will go from your home number.
Step 4 — Disable data roaming on your home SIM
- In Settings → Cellular
- Tap your home SIM (Primary / Personal)
- Turn off "Data Roaming"
This step is crucial: it prevents your home SIM from using data in Japan (which would cost you a lot in overage charges). All data will go through the PlanJapan eSIM.
Step 5 — Verify everything works
In your iPhone's status bar, you should see:
- Two network indicators (one for each line)
- The 4G or 5G symbol next to the PlanJapan line
Open Safari, launch Google Maps — if the page loads, your dual SIM is operational.
Setting up dual SIM on Android and Samsung
The logic is identical on Android, but menus differ slightly by brand. Here's the procedure for Samsung Galaxy and other Android devices once your PlanJapan eSIM is installed:
Samsung Galaxy (One UI)
- Go to Settings → Connections → SIM Card Manager
- You'll see your two lines: home SIM and PlanJapan eSIM
- Under "Mobile data", select PlanJapan eSIM
- Under "Calls", select your home SIM
- Under "Messages", select your home SIM
Google Pixel and other Android
- Go to Settings → Network & internet → SIM cards
- Tap your PlanJapan eSIM
- Enable "Mobile data" for this line
- Go back, tap your home SIM
- Make sure "Roaming" is turned off
Disable data roaming on Android
Just like on iPhone, this step is essential:
- Settings → Connections → Mobile Networks
- Select your home SIM
- Turn off "Data Roaming"
On Samsung, you can also access this setting directly from the SIM Card Manager by tapping on your home SIM.
Role of each SIM: the summary
To make everything clear, here's how to split functions between your two lines:
| Function | Home SIM | PlanJapan eSIM |
|---|---|---|
| Data / Internet | Disabled (roaming OFF) | Enabled — default data line |
| Outgoing calls | Default line | Not used (data-only eSIM) |
| Incoming calls | Received normally | Not applicable |
| SMS / verification codes | Received normally | Not applicable |
| WhatsApp / iMessage | Associated number | Uses PlanJapan data |
| Maps, Safari, apps | — | Uses PlanJapan data |
In summary: the home SIM handles voice and SMS, the PlanJapan eSIM handles 100% of data. Each line does what it does best.
Switching between lines: what you need to know
Once dual SIM is configured, switching between lines is automatic. But there are a few things to know:
Does data switch automatically?
Yes. Once you've set the PlanJapan eSIM as the default data line, all apps automatically use this line for internet. You don't need to do anything day-to-day.
Can you temporarily change the data line?
Yes, if needed:
- iPhone: Settings → Cellular → select the other line
- Android: Settings → SIM Card Manager → Mobile data → choose the other line
Use case: you return home and want to switch back to your home SIM. One tap is all it takes.
Do both lines work at the same time?
Yes, that's the whole point of dual SIM. You can browse the internet via the PlanJapan eSIM while receiving a call on your home SIM. Both lines are active simultaneously — no manual switching needed.
Troubleshooting: what to do if dual SIM doesn't work
Here are the most common issues and their solutions:
The PlanJapan eSIM won't connect to the network
- Check that the eSIM is enabled: Settings → Cellular → your eSIM → "Turn On This Line"
- Verify the eSIM is set as the default data line
- Toggle airplane mode on/off for 10 seconds, then try again
- Restart your phone
Data is still going through your home SIM
- Go back to Settings → Cellular → Cellular Data and make sure the PlanJapan eSIM is selected
- Turn off "Allow Cellular Data Switching" (on iPhone) — this option can automatically switch to the home SIM if the eSIM network is temporarily weak
- Verify roaming is disabled on the home SIM
I'm not receiving texts on my home SIM
- Regular SMS (including verification codes) work independently of data — they go through your carrier's voice/SMS network, even in Japan
- If you're still not receiving anything: check that your home SIM is enabled in Settings → Cellular → your SIM → "Turn On This Line"
- Contact your carrier to make sure voice/SMS roaming is included in your plan
Signal alternates erratically between both lines
- Turn off "Allow Cellular Data Switching" in Settings → Cellular (iPhone)
- If the problem persists, temporarily disable the home SIM (without removing it): Settings → Cellular → home SIM → "Turn Off This Line"
- Re-enable it — this forces a network re-registration
Frequently asked questions
Do I need a special phone for dual SIM in Japan?
No, any eSIM-compatible phone natively supports dual SIM. This includes all iPhones from the iPhone XS (2018) and most Samsung Galaxy S21 and newer, as well as Google Pixel 3+. No app or special configuration is required — the feature is built into the operating system.
Will I pay roaming on my home SIM?
Not for data, provided you properly disable data roaming on your home SIM (as explained in the guide above). For calls and texts received in Japan, most carriers include free reception in their international plan. Outgoing calls from Japan on your home SIM are charged — use WhatsApp or FaceTime via PlanJapan eSIM data instead.
Can I install the PlanJapan eSIM before leaving?
Yes, and it's strongly recommended. Install the eSIM 2 to 3 days before departure, at home, calmly. It won't connect to the NTT Docomo network until you arrive in Japan. You'll have internet from the moment you land, without hunting for a SIM counter at Narita or Haneda airport.
Is the PlanJapan eSIM data-only or does it include calls?
The PlanJapan eSIM is 100% data. It provides internet connectivity (4G/5G on the NTT Docomo network) but not phone calls or SMS. That's precisely the advantage of dual SIM: your home SIM handles calls, the PlanJapan eSIM handles data. Each does its job.
What happens if my PlanJapan eSIM plan expires mid-trip?
If your data plan expires, your phone continues working normally for calls and SMS via your home SIM. You simply lose internet access. To avoid this, choose a plan suited to your trip length — or go for the unlimited eSIM to never worry about it.
Does dual SIM drain more battery?
Slightly, yes. Two active cellular radios consume about 5 to 10% extra battery per day. In practice, it's negligible — especially since charging your phone on the Shinkansen or in cafes is easy (outlets are everywhere in Japan).
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Our recommendation
Dual SIM is the most convenient way to stay connected in Japan without losing your home number. Setup takes 2 minutes and, once in place, everything is automatic.
For a stress-free trip:
- 1 to 2 week trip → eSIM Japan 20 or 50 GB — the 50 GB is our recommendation for most travelers
- Long trip, remote work or heavy use → Unlimited eSIM Japan — zero stress, zero counter
Install your eSIM before departure, configure dual SIM following this guide, and enjoy Japan with high-speed internet from the moment you land.