If you're a foreign resident in Japan wondering how to switch mobile providers without losing your phone number, you're not alone. The good news is that Japan has a straightforward system called MNP (Mobile Number Portability) that lets you keep your existing number when you move to a new carrier. This guide walks you through the entire process — from getting your MNP reservation number to activating your new SIM — so you can switch with confidence even if your Japanese is limited.
What Is MNP and Why Does It Matter for Foreign Residents?
MNP stands for Mobile Number Portability (番号ポータビリティ, bangō pōtabiriti). It means you can leave your current carrier and join a new one while keeping the same phone number. This is especially important if you've already shared your Japanese number with your employer, your bank, or family back home.
Without MNP, switching providers means getting a completely new number — which can cause real headaches with two-factor authentication, bank notifications, and work contacts. Using MNP avoids all of that.
Before You Switch: Things to Check First
- Contract lock period: Some plans have a minimum contract period. Cancelling early may trigger a fee. Check your current contract carefully or contact your provider to confirm.
- Remaining device payments: If you bought a phone on an instalment plan, those payments continue even after you switch carriers. Make sure you understand what you still owe.
- SIM lock: Older phones bought from Japanese carriers may be SIM-locked to that carrier. You may need to request an unlock (usually free now under Japanese regulations, but confirm with your carrier) before your new SIM will work.
- Documents you'll need: Your residence card (在留カード), your current phone number, a Japanese address, and depending on the new provider, a payment method (credit card or bank account).
Step-by-Step: How to Switch Mobile Providers in Japan Using MNP
Step 1 — Get Your MNP Reservation Number from Your Current Provider
Contact your current carrier and request an MNP reservation number (MNP予約番号). You can usually do this:
- Online through your carrier's My Page account
- By phone (most carriers have an automated MNP line)
- In-store at a carrier shop
The reservation number is valid for 15 days from the date of issue. Make sure you apply to your new carrier before it expires. Some carriers may try to offer you a retention deal at this stage — that's up to you, but you are not obligated to accept it.
Step 2 — Choose Your New Provider
This is where many foreign residents face a real challenge. The major carriers — docomo, au, and SoftBank — typically require a Japanese credit card, and their in-store staff may have limited English support. If you're new to Japan or don't yet have a Japanese credit card, consider these more foreigner-friendly options:
| Provider | Japanese Credit Card Required? | Language Support | MNP Available? |
|---|---|---|---|
| GTN Mobile | No (residence card accepted) | Multilingual | Yes |
| Mobal | No | English | Yes |
| docomo / au / SoftBank | Usually yes | Limited English | Yes |
| IIJmio / OCN Mobile | Usually yes | Japanese mainly | Yes |
Plans, requirements and availability change regularly. Always confirm the latest details on each provider's official website before signing up.
When comparing plans, think about:
- Monthly data allowance and whether unused data rolls over
- Whether voice calls are included or charged separately
- Contract length and cancellation conditions
- Customer support language
- Whether a Japanese bank account or credit card is required for payment
Step 3 — Apply to Your New Provider with Your MNP Number
Once you've chosen a provider, apply online or in-store. You'll need to provide:
- Your MNP reservation number and its expiry date
- Your residence card
- Your Japanese address
- Your payment details (credit card, debit card, or bank account depending on the provider)
If applying online, your new SIM will typically be mailed to your registered address. If applying in-store, you may receive it on the same day.
Step 4 — Activate Your New SIM
Follow the activation instructions that come with your new SIM. This usually involves inserting the SIM, connecting to Wi-Fi, and completing a brief setup process via an app or website. During the switchover, there is typically a short period (often just a few minutes) when your number is inactive. Plan for this and avoid scheduling the switch during a time when you need to be reachable.
How Long Does the MNP Process Take?
The total timeline varies, but as a rough guide:
- Getting your MNP reservation number: Same day (online or by phone)
- Application review by new provider: A few hours to 1–2 business days
- SIM delivery (if ordered online): Typically 2–5 business days
- Number switchover after activation: Usually within minutes
If you apply in-store, the whole process can sometimes be completed in a single visit. Online applications take longer due to delivery time.
Costs to Be Aware Of
Fees vary by provider and plan, so treat the following as a general guide only — always check the latest figures on the official site:
- MNP transfer fee from your current carrier: As of recent regulatory changes in Japan, carriers are not supposed to charge a cancellation fee solely for MNP, but early termination fees may still apply if you're within a contract period. Confirm with your current provider.
- New SIM issuance fee: Some providers charge a one-time fee for issuing a SIM card. Others have eliminated this. Check before applying.
- Monthly plan cost: Budget MVNOs can be significantly cheaper than the major carriers. Prices change, so compare current plans directly.
Common Worries — Answered
"My Japanese isn't good enough to call my carrier."
Many carriers now offer online MNP requests in Japanese, which you can navigate with a translation app. Foreigner-friendly providers like GTN Mobile and Mobal offer support in English and other languages, making the whole process much more accessible.
"Will my phone work with a new SIM?"
If your phone is SIM-unlocked and compatible with Japanese frequency bands, it should work. Check your phone model's specifications and confirm with the new provider before you apply.
"Can I switch to a prepaid SIM using MNP?"
Most prepaid SIM providers in Japan do not accept MNP transfers — MNP is generally for postpaid (monthly contract) plans. If you want to keep your number, you'll need to choose a postpaid MVNO or carrier plan.
Summary: Switching Providers in Japan Is Manageable
Switching mobile providers in Japan as a foreign resident is very doable once you understand the MNP process. The key steps are: get your reservation number from your current carrier, choose a new provider that suits your situation (especially important if you don't have a Japanese credit card), apply with your residence card and MNP number, and activate your new SIM. The whole process can take anywhere from one day to about a week depending on whether you apply in-store or online.
If you're worried about the language barrier, providers like GTN Mobile and Mobal are specifically designed to help foreign residents navigate exactly this kind of process. Don't let the paperwork put you off — once you've switched to a plan that fits your budget and needs, you'll wonder why you waited so long.