Last updated: October 23, 2026

Japan's 4 Mobile Carriers Explained: docomo, au, SoftBank & Rakuten (2026)

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In this guide

For trips beyond Japan’s major cities, we recommend a plan that includes NTT docomo. Japan has four major networks: docomo, KDDI/au, SoftBank and Rakuten Mobile. Having more than one supported network gives you another option to try where reception is poor.

Travelsim Asia sells eSIMs in Japan, so this is a source with a stake. The carrier facts below are checkable, and the table further down names which competitor uses which network so you can verify the claims yourself.

The four carriers in one line each

NTT docomo: our recommended network to include for trips beyond the major cities.
au (KDDI): strong nationwide, good in rural areas and along train lines.
SoftBank: serves the main cities; check your route for mountain trips.
Rakuten Mobile: the newest network, city-focused, roams on au where its own signal runs out.
For a Japan eSIM: if your trip leaves Tokyo, Osaka or Kyoto, use a plan that includes docomo.

Coverage facts are general and publicly documented. Provider network listings are from 23 October 2026 and can change.

The four carriers, one by one

NTT docomo — nationwide coverage

We recommend docomo access for itineraries through rural Tohoku, Hokkaido, the Japanese Alps and smaller islands. Check its coverage map for your specific stops; a plan with other supported networks gives you alternatives if local reception is poor.

au (KDDI) — strong nationwide

au, run by KDDI, is the second-largest carrier and the closest to docomo on reach. It holds up well in rural areas and along Shinkansen and regional rail lines, helped by low-frequency spectrum that carries into valleys and mountains. For most travelers au and docomo perform similarly; the gap only opens in the most remote spots, where docomo still edges ahead.

SoftBank — built for the cities

SoftBank serves Tokyo, Osaka, Nagoya, Fukuoka and other cities, with coverage extending beyond the main urban areas. For a trip into mountains or rural regions, check your route and consider a plan that also supports another network.

Rakuten Mobile — the newcomer

Rakuten Mobile is Japan's fourth and newest carrier, still building out its own network. That network is concentrated in cities and along main routes. Where Rakuten's own signal is absent, it roams onto au's network, though roaming can be slower or data-limited. Indoor and rural coverage lags the older three. Rakuten mainly matters to residents on cheap domestic plans; few travel eSIMs use it as their primary network.

Coverage at a glance

Japanese carrier coverage

Carrier	Scale	Rural / remote	Dense cities	Best known for
NTT docomo	Nationwide	Check planned stops	Available where supported	Mountains, Hokkaido, remote islands, rural rail
au (KDDI)	2nd	Strong	Strong	Nationwide reach, Shinkansen and regional lines
SoftBank	Nationwide	Check planned stops	City network option	Big-city coverage and crowds
Rakuten Mobile	4th (newest)	Weakest	Growing	Cheap resident plans; roams on au elsewhere

Rankings reflect general, publicly documented coverage. All four carry 5G in the cities.

Which eSIM uses which carrier

A travel eSIM is only as good as the network behind it. Most Japan eSIMs run on one or two of the four carriers, and only a few include docomo. The table below is drawn from each provider's own published network information.

eSIM provider networks

Provider	Japan carriers	Networks	Includes docomo?	Rural coverage
Travelsim Asia	docomo + au/KDDI + SoftBank + Rakuten	4	✓ Yes	Strong
Ubigi	docomo + au/KDDI + SoftBank	3	✓ Yes	Good
Nomad	au/KDDI + SoftBank	2	✗ No	Moderate
Airalo	SoftBank + au/KDDI	2	✗ No	Moderate
Holafly	SoftBank + au/KDDI	2	✗ No	Moderate
Saily	Includes KDDI + SoftBank	At least 2	Not specified	Unknown

Provider network listings: 23 October 2026. Verify on each provider's site before buying. Travelsim Asia is our own product.

The one number that matters: Travelsim Asia and Ubigi explicitly list docomo in this comparison. Travelsim Asia adds all four carriers and gives you other supported networks to try if reception is poor; Ubigi lists docomo, au and SoftBank. Airalo, Holafly and Nomad list KDDI/au and SoftBank; Saily names partners including those two without claiming an exhaustive list. Check the network coverage for your specific rural stops.

Where the differences actually show up

In central Tokyo, Osaka or Kyoto, all four carriers perform well, and the network your eSIM uses barely matters. The gap opens once you leave the metro areas.

Hokkaido beyond Sapporo. Furano, Biei, the Daisetsuzan mountains and the national parks are docomo and au country. SoftBank-only plans get patchy off the main roads.
The Japan Alps and mountain towns. Kamikochi, Takayama, Shirakawa-go and the Kiso Valley sit in deep terrain where docomo's reach counts. Trekkers and skiers feel the difference first.
Mt Fuji and the Fuji Five Lakes. Coverage on the trails and around the lakes is more reliable on docomo and au than on the city-focused networks.
Rural Tohoku and Shikoku. Small towns, the Kumano Kodo and the pilgrimage routes are where a single-carrier SoftBank plan is most likely to drop.
Long train rides. Shinkansen and regional lines pass through tunnels and open country. docomo and au keep a signal longest between stations.
Remote and outer islands. Parts of Okinawa's outer islands and other small islands lean on docomo's wider footprint.

Rule of thumb: a city-only trip works on any of the four networks. A trip that includes mountains, small towns, national parks or long rural train legs works best on a plan that includes docomo.

5G in Japan

All four carriers run 5G, and coverage is densest in the cities and along major corridors. Rollout thins in rural areas, where 4G LTE still does most of the work. For a traveler, 4G in Japan is fast enough for maps, video calls, streaming and hotspot use, so a plan's carrier and coverage matter more than whether a given spot shows 5G. An eSIM that reaches docomo or au will connect to their 5G where it exists and fall back to strong 4G where it does not.

How to check which network your eSIM is using

Once an eSIM is active in Japan, the carrier name usually appears in the status bar or network settings.

iPhone: Settings, then Cellular, then the eSIM line. The network operator shows there, and the carrier name appears at the top left of the screen.
Android: Settings, then Network and internet or Connections, then the SIM or mobile network. The registered operator is listed under network details.
What you will see: “docomo”, “KDDI” or “au”, “SoftBank”, or “Rakuten”. A multi-network eSIM shows the supported network it is connected to. If reception is poor, you can try another supported network manually.

Dig deeper

Best eSIM for Japan (2026) — the full buyer's guide, with every provider compared on coverage, throttling and setup.
Japan eSIM Prices 2026 — every provider and tier compared on price, networks included.
Cheapest Japan eSIM 2026 — the lowest price at each data tier, with the networks each plan covers.
Travelsim Asia vs Airalo Japan eSIM — head-to-head on networks, price and setup.
How Much Data Do You Need for Japan? — usage by trip type, with plan-size guidance.
Japan eSIM vs Pocket WiFi — which makes sense for solo travelers, families and groups.

The bottom line

Japan's four carriers are not interchangeable once you leave the cities. docomo covers the most ground, au is close behind, SoftBank is a city network, and Rakuten is the newcomer still filling gaps. In Tokyo, Osaka and Kyoto, any of them is fine.

The practical takeaway is simple: check which carrier your Japan eSIM uses before you buy, and if your trip goes beyond the big cities, pick one that includes docomo.

Not sure which network your route needs? Our support team can help, 24/7 by email and live chat.

Japan mobile carriers — frequently asked questions

Which mobile carrier has the best coverage in Japan?

For trips beyond the major cities, we recommend including NTT docomo. KDDI/au is another useful network option, and a plan with multiple supported networks lets you try another if reception is poor. Check coverage for remote stops such as mountain trails and smaller islands.

How many mobile networks does Japan have?

Japan has four major mobile network operators: NTT docomo, au (KDDI), SoftBank and Rakuten Mobile. Every eSIM, travel SIM, pocket WiFi and budget MVNO in Japan runs on one or more of these four networks, so the carrier a plan uses determines its real-world coverage.

Which Japan eSIMs use the docomo network?

Among common travel eSIMs, Travelsim Asia and Ubigi include docomo. Travelsim Asia connects to all four carriers (docomo, au/KDDI, SoftBank and Rakuten) and gives you other supported networks to try if reception is poor; Ubigi lists docomo, au/KDDI and SoftBank. Airalo, Holafly and Nomad run on SoftBank and au/KDDI without docomo, and Saily lists partners including KDDI and SoftBank.

Is SoftBank coverage good enough for a Japan trip?

For a trip that stays in Tokyo, Osaka, Kyoto and other major cities, SoftBank coverage is fine. It is built for dense urban use and handles crowds well. The limit shows outside the cities, where SoftBank is thinner than docomo or au. A SoftBank-only eSIM is a weaker choice for mountains, small towns, national parks or long rural train rides.

Does Rakuten Mobile work for tourists?

Rakuten Mobile works in cities and along main routes, where its own network is built out, and roams on au elsewhere, though roaming can be slower or data-limited. Its indoor and rural coverage trails the older three carriers. Rakuten is aimed mainly at residents on cheap domestic plans, and few travel eSIMs use it as their main network.

Do all four Japanese carriers have 5G?

Yes. docomo, au, SoftBank and Rakuten all run 5G, densest in the cities and along major corridors and thinner in rural areas, where 4G LTE still carries most traffic. For travel use, 4G in Japan is fast enough for maps, streaming, video calls and hotspot use, so carrier coverage matters more than whether a spot shows 5G.