Situation Guide
The English Teacher's Guide to SIMs in Japan (ALT & JET)
Sponsored / Contains affiliate links
If you only read this part
You will land in Japan without a Japanese credit card or bank account, which locks you out of the cheap monthly plans. The standard play is two-stage: get a number immediately through Mobal or similar (they take foreign cards), then MNP your number to LINEMO (city placements) or ahamo (rural placements) once your salary account and card exist, around month two or three.
If your school is rural or mountainous, the docomo network (ahamo) is the safe choice.
Section 01
The First-Month Wall: No Japanese Payment Method
The cheap plans (LINEMO, povo, ahamo) require a residence card plus a Japanese payment method, usually a Japan-issued credit card. A freshly arrived teacher has neither, which narrows your options to services that accept foreign cards.
The standard picks at this stage are Mobal and Sakura Mobile. They cost more, but you get a Japanese phone number immediately, and you will need one fast: board of education paperwork, opening a bank account, renting an apartment. Everything number-dependent hits in your first weeks. Details in our no-credit-card SIM guide.
Section 02
Pick Your Network by Placement
- Rural or mountain placementahamo (docomo network) is the first choice. It minimizes the risk of your school or commute being a dead zone. JET placements skew rural, and schools in the hills are common.
- City placementLINEMO (SoftBank network) is fine. The signup flow is comparatively clear, and you keep the option of dropping to the 990-yen 3GB tier.
- School event congestionSports day and graduation pack thousands of phones into one field; every network slows down. Checking whether the staff room has usable Wi-Fi matters more than the carrier choice here.
Section 03
When to Switch
Japanese credit card approvals get realistic around your second or third paycheck, once income history exists. Once you have a card, MNP lets you keep your number and cut your monthly bill substantially. The number you got through Mobal comes with you. Steps are in our MNP guide.
One shortcut: LINEMO accepts bank transfer payment, so you can switch as soon as your salary account is active, without waiting for a credit card at all.
Section 04
Data Reality at School
Plenty of schools have no staff Wi-Fi that teachers can actually use. Lesson-prep videos, downloading materials, translation apps: consumption runs higher than you expect, and 20 to 30GB a month is the realistic budget. A 3GB plan only works if both your apartment and your school have solid Wi-Fi.
The Verdict
The Teacher Setup
Month one (arrival to bank account)
Mobal
Takes foreign cards, gives you a Japanese number immediately. The premium price is the cost of getting a number when you need one.
Month two or three onward
ahamo or LINEMO
Rural placement: ahamo (2,970 yen, 30GB, docomo network). City placement: LINEMO (990 to 2,970 yen). Either way, MNP keeps your number.
FAQ
Frequently asked questions
Can I sign up before I have my residence card?
Generally no. But you receive your residence card at the airport on landing (at major airports), and online applications work from that moment.
Will my school give me a phone?
Almost never. Your own phone on your own contract is the standard, even when the school requires specific contact apps.
Is cancelling a hassle when my contract ends and I leave Japan?
Cancellation fees are gone on the major plans and the process is online. Steps and pitfalls are in our cancellation guide.