A data-only eSIM for Japan adds a second line to your phone for internet while your existing number stays active for calls and two-factor codes. On 10 September 2026 a 10 GB, 30-day plan cost €16.00 at both Yesim and Airalo. The choice that matters is which Japanese network the plan runs on, because that decides coverage outside the cities.
Our estimate, not a measurement, is roughly half a gigabyte a day on maps, messaging and browsing, and two or three with video. A ten-day trip on ordinary use lands near five gigabytes. The reasoning, the setup steps and the questions that are the same in every country are on how a travel eSIM works. This page is the part that is specific to Japan.
An eSIM does not have its own network. It rents capacity from a Japanese carrier, and which one it rents from is what determines whether you have a signal on a valley in Nagano.
| Network | Where it is strongest | Worth knowing |
|---|---|---|
| NTT Docomo | Broadest rural, mountain and Hokkaido coverage | The safe default if your trip leaves the main cities. Ubigi is the only provider in our table naming it |
| SoftBank | Cities and the Tokaido corridor | Airalo names it with KDDI, Nomad names it with KDDI au |
| KDDI (au) | Cities, strong along main rail lines | Named by Airalo, Nomad and Ubigi, each pairing it with another network |
| Rakuten | Urban centres | Thinnest of the four outside cities. No provider in our table names it |
If a listing does not tell you which network it runs on, that omission is itself information. The plans confident about their coverage say so in the first line.
The two partners and two reference providers, read on the same night, per plan, before checkout. The column that matters is the last one. Yesim’s page lists NTT Docomo, SoftBank and KDDI as Japan’s providers but does not say which one its plan runs on. Airalo states SoftBank and KDDI. Nomad names KDDI au and SoftBank, Ubigi names KDDI and NTT Docomo, so Ubigi is the only one of the four naming Docomo, the network with the widest rural reach on its own map.
| Provider | Plan | Data | Days | Price | Network |
|---|---|---|---|---|---|
| Yesim | 5 GB, 30 days read at yesim.app/country/japan/ | 5 GB | 30 | €8.80 | not stated by the provider |
| Yesim | 10 GB, 30 days read at yesim.app/country/japan/ | 10 GB | 30 | €16.00 | not stated by the provider |
| Yesim | 20 GB, 30 days read at yesim.app/country/japan/ | 20 GB | 30 | €24.80 | not stated by the provider |
| Yesim | 7 days unlimited read at yesim.app/country/japan/7days-unlimited-esim-data-plan/ | Unlimited, fair-use throttle, threshold not stated | 7 | €24.50 | not stated by the provider |
| Yesim | 15 days unlimited read at yesim.app/country/japan/15days-unlimited-esim-data-plan/ | Unlimited, fair-use throttle, threshold not stated | 15 | €36.00 | not stated by the provider |
| Airalo | Moshi Moshi 5 GB, 7 days read at airalo.com/japan-esim/moshi-moshi-7days-5gb | 5 GB | 7 | €9.00 | SoftBank and KDDI, as Airalo states |
| Airalo | Moshi Moshi 10 GB, 30 days read at airalo.com/japan-esim/moshi-moshi-30days-10gb | 10 GB | 30 | €16.00 | SoftBank and KDDI, as Airalo states |
| Airalo | Moshi Moshi 20 GB, 30 days read at airalo.com/japan-esim/moshi-moshi-30days-20gb | 20 GB | 30 | €22.50 | SoftBank and KDDI, as Airalo states |
| Airalo | Moshi Moshi 7 days unlimited read at airalo.com/japan-esim | Unlimited, 3 GB/day full speed then 1 Mbps | 7 | €24.00 | SoftBank and KDDI, as Airalo states |
| Airalo | Moshi Moshi 15 days unlimited read at airalo.com/japan-esim | Unlimited, 3 GB/day full speed then 1 Mbps | 15 | €43.00 | SoftBank and KDDI, as Airalo states |
| Nomad reference | 5 GB, 30 days | 5 GB | 30 | €8.61 | KDDI au, SoftBank |
| Nomad reference | 10 GB, 30 days, on sale from €15.50 | 10 GB | 30 | €13.78 | KDDI au, SoftBank |
| Nomad reference | 20 GB, 30 days, on sale from €22.39 | 20 GB | 30 | €19.81 | KDDI au, SoftBank |
| Nomad reference | 7 days unlimited | Unlimited, daily allowance then 512 kbps, allowance not stated | 7 | €21.53 | KDDI au, SoftBank |
| Nomad reference | 14 days unlimited | Unlimited, daily allowance then 512 kbps, allowance not stated | 14 | €35.31 | KDDI au, SoftBank |
| Ubigi reference | 10 GB, 30 days | 10 GB | 30 | $16.50 | KDDI, NTT Docomo |
| Ubigi reference | 15 days unlimited | Unlimited, 30 GB full speed then 2 Mbps | 15 | $39.00 | KDDI, NTT Docomo |
Observed 10 September 2026 17 plans Method
Read by hand on each provider's public plan page, per plan, before checkout, in the currency the page displayed. Prices change and promotions come and go. Partner rows link through our tracked redirect to the provider’s site, not to the plan page, and earn us a commission; the page each of those prices was read from is printed under the plan name. Rows marked reference are providers we do not earn from, and link to the page they were read from. Ubigi’s prices are in US dollars because that is what its page displays. What each provider means by the word unlimited, and which of the four publishes a number, is set out under the table.
Every page that answers this hands you a gigabyte range and leaves you to guess. The more useful question is what the guess costs. On the prices above, read 10 September 2026, the step from a 10 GB to a 20 GB 30-day plan was €8.80 at Yesim, €6.50 at Airalo and €6.03 at Nomad. That is the price of not having to think about it again.
Two weeks on 20 GB is 1.43 GB a day. Two weeks on 10 GB is 0.71 GB a day. Three weeks on 20 GB is 0.95 GB a day. Pick the row whose daily figure you would not have to ration, then pay the step-up rather than try to forecast your own consumption. We do not measure anyone’s usage and neither does anyone else quoting you a number.
| Plan | Price as displayed | Per gigabyte | Cost of the next size up |
|---|---|---|---|
| Yesim, 5 GB, 30 days | €8.80 | €1.76 | €7.20 to reach 10 GB |
| Yesim, 10 GB, 30 days | €16.00 | €1.60 | €8.80 to reach 20 GB |
| Yesim, 20 GB, 30 days | €24.80 | €1.24 | No larger plan recorded |
| Airalo, 10 GB, 30 days | €16.00 | €1.60 | €6.50 to reach 20 GB |
| Airalo, 20 GB, 30 days | €22.50 | €1.13 | No larger plan recorded |
| Nomad, 5 GB, 30 days | €8.61 | €1.72 | €5.17 to reach 10 GB |
| Nomad, 10 GB, 30 days | €13.78 | €1.38 | €6.03 to reach 20 GB |
| Nomad, 20 GB, 30 days | €19.81 | €0.99 | No larger plan recorded |
| Ubigi, 10 GB, 30 days | US$16.50 | US$1.65 | No larger fixed plan recorded |
Airalo’s 5 GB plan runs 7 days rather than 30, so it is not on this ladder. Ubigi stays in US dollars because that is the currency its page displays, and no exchange rate is applied anywhere on this page. Prices move, so re-read the table date before you rely on the arithmetic.
Unlimited means an allowance at full speed and a slower connection after it. Three of the four providers publish the number, and one does not. Read 15 September 2026, Airalo’s fair-use policy states that when you use more than 3GB in a day it slows your speed to 1 Mbps for the rest of that day, with the allowance resetting every 24 hours counted from the time you activated the eSIM. Ubigi’s 15-day Japan plan at US$39 states 30GB of full speed data, then optimised to 2 Mbps.
Nomad publishes a figure twice on the same page and the two do not agree. The plan data behind its Japan unlimited packages reads 2GB/day at 4G/5G, 1 Mbps after 2GB, while the explainer paragraph above the plans says you continue at a throttled speed of 512kbps once the daily allocation is used, without naming that allocation. Both were read 15 September 2026. Our price table above carries the 512kbps wording because that is what we recorded on 10 September, before we read the plan data. Read the plan you are buying rather than the explainer.
Yesim is the one that publishes no figure at all. Its Japan plan page states only that data speed may be limited in accordance with the network operator’s fair usage policy, and the policy page it links to names no threshold either. A blank cell below is not a gap in our reading, it is what the page publishes.
| Provider | What the page calls it | Full-speed threshold | After the threshold |
|---|---|---|---|
| Yesim | The network operator’s fair usage policy | not published | Speed may be limited, no figure published |
| Airalo | Unlimited Data Plans Fair Use Policy | 3 GB a day, resetting 24 hours after activation | 1 Mbps for the rest of that day |
| Nomad, unlimited plans | Plan data reading 2GB/day at 4G/5G | 2 GB a day, reset 24 hours from activation | 1 Mbps on the plan data, 512 kbps in the page explainer |
| Ubigi, 15-day plan | Fair Use Policy | 30 GB across the plan | 2 Mbps |
Read 15 September 2026 at yesim.app/country/japan/, airalo.com/m/resources/unlimited-data-plans-fair-use-policy, nomadesim.com/japan-esim and cellulardata.ubigi.com/rates-and-coverage/japan-data-plans/japan-unlimited-15-days/. Nomad’s 2GB figure sits in the plan data its own page renders, its 512kbps figure in the explainer paragraph above the plans, and the two do not agree. Partner pages are named rather than linked, because every link of ours to a partner is tracked.
On all four providers above the hotspot draws on the same allowance as the phone, and none of them publishes a separate tethering figure. Airalo is the only one that says so in as many words. Read 15 September 2026, its fair-use policy states that you can use your device as a personal hotspot and that there is no limit on tethering or the number of devices you connect, which also means everything you share counts against the same 3 GB day.
A carrier sells the same feature differently. T-Mobile’s own U.S. Pass eSIM, read the same day, publishes a hotspot allowance separate from the phone allowance, 14GB on the 7-day pass at US$25, 20GB on the 10-day at US$30 and 28GB on the 14-day at US$35, against 50GB of premium data on the phone, and its own page says the hotspot continues at reduced speed once that allowance is gone. A travel eSIM that names no hotspot figure is not being more generous, it simply has one pool.
For two adults and a tablet in Japan that collapses the hotspot question back into the sizing question above. Two tablets on a 3 GB day is still a 3 GB day.
| Provider | What the page states | Where hotspot data comes from | Separate hotspot figure |
|---|---|---|---|
| Yesim | Plan details list the hotspot as available | The plan allowance | not published |
| Airalo | Personal hotspot allowed, no limit on tethering or devices | The same 3 GB day | not published |
| Nomad | Hotspot and tethering supported | The plan allowance | not published |
| Ubigi | Data sharing allowed | The plan allowance | not published |
| T-Mobile, on its own U.S. Pass eSIM | High-speed mobile hotspot data listed per pass | A pool of its own | 14GB, 20GB and 28GB by pass length |
Read 15 September 2026 at yesim.app/country/japan/, airalo.com/m/resources/unlimited-data-plans-fair-use-policy, nomadesim.com/japan-esim, cellulardata.ubigi.com/rates-and-coverage/japan-data-plans/japan-unlimited-15-days/ and the T-Mobile page linked below.
Install on wifi before you fly, switch the travel line on when you land, and leave the home line alone so your number and your codes keep working. The three steps, and the mistake that locks people out of their bank, are on the shared guide.
| Option | Best when | Cost against it |
|---|---|---|
| Travel eSIM | One or two people, phone-first use | Needs a compatible, unlocked phone |
| Pocket wifi | Three or more people, or laptops in daily use | A device to carry, charge and return |
| Home carrier roaming | Very short trips, or where a day pass is genuinely cheap | Usually the most expensive over a fortnight |
The table above is what the plans cost. These are the two providers we earn from. Airalo states SoftBank and KDDI, Yesim does not state a network, and neither names Docomo.
An eSIM installs before departure and connects the moment the plane doors open. Your number and your 2FA codes stay on your existing SIM.
See plansFixed data bundles with no contract. Useful for short trips where an unlimited plan costs more than the data you will actually use.
See plansNo. A data-only travel eSIM adds a second line for internet. Your existing number stays on your physical SIM or on your primary eSIM, and it remains the number people reach you on, provided you leave that line enabled.
Install before you fly, activate on arrival. Installation needs a working internet connection, which is exactly what you will not have at the airport in Japan. Most providers let you install the profile early and start the validity period later.
This is the question that decides coverage, and most listings bury it. Docomo has the broadest rural and mountain coverage, SoftBank and KDDI are strong in cities and along the main corridors. If a plan does not name its host network, treat that as an answer.
In towns and along rail lines, generally yes. In the mountains, on hiking trails and in parts of Hokkaido, coverage depends entirely on the host network, and this is where Docomo-backed plans pull ahead. Do not assume city performance transfers.
It depends on the host network, and we have not measured it. Of the plans in our table Airalo names SoftBank and KDDI, Nomad names KDDI au and SoftBank, Ubigi names KDDI and NTT Docomo, and Yesim names none. Signal in the long tunnels is what each carrier claims on its own coverage map, not something we tested. Treat it as a purchase question, and buy the plan that names a network whose map you can check.