1. What most travellers need
Maps, translation and messaging work fine on a 5–20 GB data plan for a one-to-two-week trip. Public Wi-Fi exists at stations and airports, but it is not reliable enough as the only option.
Check that your phone is unlocked and supports eSIM before buying a data plan, and confirm the coverage areas, speed caps and hotspot rules.
2. Travel eSIM: fastest to set up
A travel eSIM is installed before departure and activates when you land, usually with 5–20 GB data tiers. It keeps your original SIM for calls and messages.
eSIMs are the most convenient for one phone; the price per GB is often higher than a local SIM, and some providers throttle video or restrict sharing, so read the fair-use rules.
3. Pocket Wi-Fi: best for groups
Pocket Wi-Fi devices provide a personal hotspot for several phones, laptops and tablets at once, which makes them economical for groups or long stays.
They need a deposit, daily rental and charging, and the device must be returned or posted back. Pick-up and drop-off at airport counters is common in Japan.
4. Local SIMs and prepaid data
Prepaid data SIMs sold at airports, electronics stores and convenience stores offer competitive per-GB prices and are simple to activate, though voice calls are usually separate.
Some require registration with passport details; most are data-only for tourists. Compare the validity period with your trip length so the data does not expire early.
5. Common mistakes
Common mistakes include buying a plan without checking coverage on rural routes, assuming unlimited plans have no speed caps, forgetting that pocket Wi-Fi needs daily charging, and arriving without any data option while relying on patchy public Wi-Fi.
Another is not saving offline maps and translation packs: they work without a signal and reduce data use in the subway and mountains.
6. Checklist before departure
Before departure: confirm the phone is unlocked and eSIM-compatible; compare eSIM, pocket Wi-Fi and a local SIM for your trip length and device count; save offline maps and a translation pack; and keep a small cash reserve for trains and vending machines.