Dual SIM: two lines in a single phone
It's the question we're asked most before departure: “can I keep my number in Japan?”. The answer is two words: dual SIM. Your phone can run two lines at once — your usual SIM card and an eSIM. The PlanJapan eSIM replaces nothing: it is added.
In practice, your home number stays active from take-off to your return, and the eSIM handles the internet only, on the NTT docomo 4G/5G network. Here's the layout:
Calls, texts, number. It stays in the phone, your number stays reachable and receives texts. Its data roaming: switched off. ✓ Kept.
All the data. Google Maps, WhatsApp, social media: everything goes through it, on the NTT docomo 4G/5G network. Data in Japan.
You stay reachable on your usual number, and all your browsing goes through PlanJapan — with no risk of roaming charges on your home line.
The 3 settings to sort out before departure
In Settings → Mobile Data, select the PlanJapan eSIM for data. This is the setting that does everything: your browsing runs through Japan, not through your home plan.
On your home line, turn off data roaming. It keeps receiving calls and texts, but will never use data while roaming.
Don't disable your home line: it's what keeps your number reachable. The two lines coexist without interfering. The step-by-step detail is in our installation guide.
Banks and verification codes: everything keeps working
This is travellers' number one worry — and precisely why keeping your home number in Japan matters. Because your personal line stays active, texts arrive normally: your bank's code to confirm a payment, an app login code, a booking confirmation. Receiving a text uses no data; depending on your home carrier, reception fees may apply outside Europe — a quick look at their price list before departure and you're set.
On the app side, everything runs on PlanJapan data: your banking apps work without a VPN — nothing is blocked.
And for calls and messages?
The PlanJapan eSIM handles data only — that's what makes it so simple. For calls and messages, use WhatsApp, iMessage or FaceTime: they go through the internet, with your usual number kept as a dual SIM. Your family won't notice any difference. We explain it all in our guide to calls & texts in Japan.
The right habit: check both lines when you landPersonal line switched on (data roaming OFF) + PlanJapan eSIM selected for data. Two ticks, and you're set.
