How to Choose a Japan SIM Card: Networks, Days, and Price Explained

Japan's network landscape

Japan's major mobile carriers are NTT docomo, KDDI au, SoftBank, and Rakuten Mobile. Travel SIM plans generally run on one of these networks, and the plan listing states which one.

5G coverage is mature in major cities like Tokyo, Osaka, Kyoto, Nagoya, and Fukuoka, and along the Shinkansen route. Hokkaido, Tohoku, mountain areas, and remote islands are mostly 4G LTE — plenty for everyday navigation and messaging. Subway stations generally have signal.

Does the choice of network matter?

In major cities, the day-to-day difference between the three networks is minor. What's worth noting is rural and mountain areas — docomo traditionally has denser tower coverage in the countryside, while Rakuten's own network is concentrated in cities (relying on roaming elsewhere).

If your trip stays mostly in cities and along the Shinkansen route, the network choice matters less; if you're heading somewhere like Shirakawa-go, Kamikochi, or Yakushima, check which network the plan runs on.

How trip length maps to plan length

• The day count starts from the day you first connect to a Japanese network, not the day you buy it. So buying and installing it early costs you nothing.
• Buy one extra day as a buffer. Overnight flights, delays, and itinerary changes often mean you end up using it one day longer than planned.
• If your trip is split into two legs (e.g. flying back to Hong Kong in between), note that the day count runs continuously and doesn't pause.

How much data is enough?

For most independent trips to Japan, data demand mainly comes down to three things: Google Maps navigation, checking train transfers, and uploading photos.

• Pure sightseeing, not much video → 1GB a day is plenty.
• Livestreaming, uploading videos, or video calls regularly → 2–3GB a day or more.
• A family sharing one hotspot device → multiply roughly by the number of people, or consider buying a second card.
• Saving tip: download offline maps for Tokyo or Osaka in Google Maps before you leave.

eSIM or physical SIM?

If your phone supports eSIM (dial *#06# and check for an EID), go with eSIM — it activates instantly after payment, no waiting for delivery, and no risk of “the card hasn't arrived but I need to leave.”

If your phone doesn't support it (e.g. a mainland China iPhone), or you want to lend an older phone to a family member, go with a physical SIM card. We ship locally within Hong Kong, typically arriving in 1–3 working days — remember to allow for that.

Most common problems after landing

• Can't get online → Nine times out of ten it's because “data roaming” isn't turned on. Settings → Cellular → select the eSIM → turn on data roaming.
• Only one or two bars of signal → Manually select the network stated on the plan (e.g. SoftBank) in network selection.
• Very slow speeds → Check whether you've used up your daily allowance and been throttled; daily-allowance plans reset automatically the next day.