Getting a Phone and SIM in Japan

Setting up phone service for life in Japan is two jobs at two different times: before you leave the US, keep your US number, and after you arrive, get a Japanese number. The first is the one people regret skipping — it’s tied to your US banking and two-factor codes, and it’s hard to fix once you’ve gone — so start there.

Before you leave the US

Keep your US number — and don’t just cancel it

Your US mobile number is the login and two-factor (2FA) number for your US bank, brokerage, and government accounts. Cancel it carelessly and you can lock yourself out of your own accounts from the other side of the Pacific.

• The FCC’s guidance is to port the number first and cancel second — never end your old service before moving the number somewhere, because a released number can be lost for good.
• Porting out needs your account number and a transfer PIN, which you can only get from the carrier while the line is still active.

Where to keep it

Two routes, depending on how much your bank leans on text-message codes:

The standout for most US persons is a cheap US cellular plan with WiFi calling: it’s a genuine cellular number (so it clears bank 2FA), and with WiFi calling switched on you can use it from Japan over any WiFi for calls and texts — including 2FA codes — at no roaming cost. Tello, for instance, includes WiFi calling free; just confirm it works where you’ll be, since some countries block it.

Pick a carrier that tolerates living abroad. Many US carriers suspend or cancel a line that spends too long off the US network — Google Fi after ~90 days mostly overseas, and prepaid lines simply lapse if you don’t periodically use or refill them (AT&T, for one, cancels a prepaid line about 60 days after its balance expires). Low-cost MVNOs like Tello and US Mobile are popular with expats for being forgiving here. (Examples, not endorsements — TaiganJP earns no commission from any service named here; confirm current terms.)

Before you fly: activate, test, unlock

• Activate it in the US. You generally can’t activate a fresh US line from Japan — activation needs the US network — so set it up while you’re still stateside.
• Test it. Point your important accounts at the number (or, sturdier, move their 2FA to an authenticator app), and confirm you can actually receive your bank’s login codes while problems are still easy to fix.
• Unlock your phone. A US-carrier handset may be SIM-locked; have it unlocked before you go so it’ll accept a Japanese SIM. (Phones sold in Japan have shipped unlocked since October 2021, but yours is American.)

After you arrive: a Japanese number

Get online on day one

A full Japanese contract usually wants a Japanese bank account (and sometimes a credit card), which you won’t have immediately. So most people bridge the gap with a data eSIM or prepaid SIM bought before landing — it works the moment you arrive on an unlocked, eSIM-capable phone — then switch to a proper plan once they’re set up.

Sign up for a Japanese line

You’ll need identity verification (本人確認honnin kakunin) — your 在留カードzairyū kādo — and usually a Japanese bank account or card for billing. Then it comes down to which kind of provider:

(Provider examples, not endorsements — TaiganJP earns no commission, and plans, payment options, and airport counters change, so confirm the current details on each provider’s own site.)

A data-only SIM is a fine choice if you keep calls and texts on your US number (via WiFi calling or Google Voice).

Carry both numbers: dual SIM

Most modern phones run two lines at once — typically one physical SIM plus one eSIM (recent iPhones and Pixels also support two eSIMs), and both lines can call and text. The common expat setup is the US number on one line for 2FA and calls home, and a Japanese SIM on the other for data and local calls. Two notes: your phone uses one data network at a time (make the Japanese line your data line), and the “don’t leave it unused abroad” warning still applies to the US line — so a flexible US carrier matters here too.

Match the plan to how long you’ll stay

• Months: a prepaid or data SIM, or an eSIM — don’t sign a long contract.
• A year or more: a carrier or MVNO plan. Japan capped early-cancellation fees (to around ¥1,000) and ended the punitive old “two-year lock-in,” so leaving a plan early is no longer expensive — but still read the terms.
• If you later switch Japanese carriers, MNP lets you keep your Japanese number — free online and, since 2023, “one-stop” through the carrier you’re moving to.

The short version

• Before you leave: keep your US number — don’t cancel it (port first), park it on a cheap US plan with WiFi calling (a real number, usable from Japan, best for bank 2FA) or on Google Voice (free, but the VoIP-2FA catch), activate and test it in the US, and unlock your phone.
• Pick a flexible US carrier — some drop a line used too long off the US network; Tello and US Mobile are common expat choices.
• On arrival: start with a data eSIM, then a Japanese line — foreigner-friendly (Mobal / Sakura Mobile / GTN Mobile: easy but pricier) or a budget MVNO (IIJmio / mineo: cheaper, Japanese-language).
• Dual SIM carries both numbers at once; size the plan to your stay (cancellation fees are small now); MNP keeps your Japanese number if you switch.

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This guide is general information, not legal or financial advice. Carrier requirements, plans, and the rules around identity verification and number portability change over time — verify current details with the carrier and the official sources below, and confirm your bank’s 2FA options before you move. See Your First Two Weeks in Japan for where this fits, Your Residence Card for the ID you’ll need, and Opening and Managing Japanese Bank Accounts for the account most contracts require.