Docomo vs SoftBank vs au: Which Japan Network Does Your eSIM Use?

Japan has three long-established national mobile networks, NTT Docomo, SoftBank and KDDI (sold as au), plus a newer fourth network from Rakuten Mobile. When you buy a travel eSIM, it rides on one or more of these networks. This guide explains who they are, how a travel eSIM uses them, which network each provider in our comparison lists, and how to read the official coverage maps for your own route.

One thing this page does not do is name a fastest network. We have not run speed tests, and published claims about which network is quickest rarely describe the connection a visitor’s eSIM actually gets.

The short answer

For Tokyo, Osaka, Kyoto and the main rail corridors, the network behind your eSIM is unlikely to be the deciding factor. Each of the three main operators covers Japan’s cities and major routes extensively. Allowance, validity, hotspot terms and activation rules usually matter more to the buying decision.

The network becomes worth checking when your itinerary includes mountains, remote islands, long hikes or small villages. In those places the official coverage maps can differ, and a package that lists two networks may give your phone a second option.

Japan’s mobile networks explained

NTT Docomo

Docomo is the mobile arm of the NTT group, which grew out of Japan’s former national telephone company. It runs its own nationwide network and is often listed as a partner by travel eSIM providers. Its own lower-cost online plan is sold under the ahamo name.

SoftBank

SoftBank Corp. runs the network that was Vodafone’s Japanese business before SoftBank acquired it in 2006. It operates a national network under the SoftBank brand and also runs the Y!mobile and LINEMO brands on the same infrastructure.

KDDI and au

KDDI is the company; au is the brand most travelers see. A listing that says “KDDI”, “au” or “KDDI (au)” refers to the same network. KDDI also runs the UQ mobile and povo brands.

Rakuten Mobile

Rakuten Mobile is the newest operator with its own national network. Use its official area page to check the coverage legend and locations on your route.

Airalo: SoftBank / KDDI (au) / Rakuten on current Moshi Moshi listings; check the selected package. The 11 fixed-data and six unlimited Moshi Moshi listings include these networks. Airalo’s explanatory text still names only SoftBank and KDDI, so confirm the network details of the package you buy. Network listing checked Nov 5, 2026 · Airalo network source

Sub-brands and MVNOs

Japan also has many MVNOs (mobile virtual network operators), which rent capacity on one of the big networks and sell service under their own name. Some travel eSIMs are built on similar wholesale arrangements, so the network name on your phone may not match the brand you bought from.

How travel eSIMs connect to Japanese networks

There are two common arrangements. Providers do not always say which one a package uses, and both can work well.

Roaming through a foreign carrier

Many travel eSIMs are issued by a mobile operator outside Japan. When you land, your phone connects to a Japanese network through a roaming agreement with a supported local operator. This is why setup instructions tell you to turn on data roaming for the travel line: from the phone’s point of view, you are roaming.

Your status bar may show a Japanese operator name while your traffic is routed back through the issuing operator. That can affect which country websites think you are in and, sometimes, latency.

Local or MVNO arrangements

Some packages use a Japanese partner or MVNO instead. In that case the eSIM may behave more like a domestic line on the host network. Whether 5G, particular bands or tethering are included depends on the arrangement, not just the network name.

Why the listed network can vary by package

Providers often sell several Japan products from different wholesale partners. A short, cheap plan and a larger or unlimited plan from the same brand can sit on different networks. Partners can also change between catalogue updates. Some Wanderly plans name NTT Docomo and IIJ, while other opened plans list only network types. Klook’s network varies by listing and supplier. Treat the network details for the exact package you are about to buy as the ones that count.

Which network does each Japan eSIM use?

The table below shows the network and hotspot terms each provider lists for Japan in our data. Read each review for the wider picture, including activation and top-up rules.

We’re run by the team behind Wanderly and earn money from Wanderly purchases. Read our full disclosure.

Networks and hotspot terms as each provider lists them for Japan. A package can use a different network from the one shown, so check the plan page before buying.

Two networks in one listing usually means the profile is allowed to register on either. Your phone normally picks the network automatically, and many phones let you choose one by hand in the mobile network settings if automatic selection struggles. It does not mean your phone uses both at once.

If a specific network matters to you, check the product page for the exact package before you pay. For the price side of the same providers, use the full Japan eSIM comparison and pick a plan with enough validity for your whole stay.

City and rural coverage: what the official maps show

In big cities, the practical differences between the three main networks are small for most visitors. Indoor reception in basements and large stations depends more on the building than the operator.

Outside the cities, the published maps are where differences become visible. Mountain valleys, sparsely populated coastlines, small islands and high hiking routes are where one operator may show coverage and another may not. The only honest way to compare is to look up the places you will actually be, on each map, rather than rely on a general reputation. Our guide to using an eSIM in rural Japan walks through route planning, offline preparation and backup options.

Official coverage maps

These are the operators’ own maps. Most of the detailed maps are in Japanese; a browser’s built-in translation is usually enough to read the legend.

• NTT Docomo: service area map (Japanese) and the English network and area page.
• SoftBank: service area map (Japanese).
• KDDI / au: English area map and the Japanese area map.
• Rakuten Mobile: network and area page (Japanese), which shows Rakuten’s own and partner coverage.

How to read a coverage map

Search for each place by name, then zoom in rather than reading the whole prefecture at once. Check what the legend means: maps usually separate 5G, 4G LTE and areas where service is limited or expected soon. Most maps estimate outdoor coverage, so a shaded area does not guarantee signal inside a building or a car.

Remember that the map shows the operator’s network for its own customers. A travel eSIM roaming onto that network may not have access to every band or to 5G. Use the map to rule out obvious gaps, not to predict speed.

Why we do not rank the networks by speed

Speed depends on the place, the time of day, the handset and its bands, local congestion and how the travel eSIM is arranged with the host network. Tests of domestic contracts would not tell you what your roaming eSIM will do at your hotel.

We would only publish a comparison after running the same devices on the same routes at recorded dates. We have not done that, so there is no speed table here.

Phone compatibility and frequency bands

Before worrying about the network, confirm that your phone is unlocked and supports eSIM. Phones sold for one market do not always support every band used in Japan, and regional variants of the same model can differ. A 5G icon means a 5G connection is available, not that it will be faster than 4G.

For setup steps, compatibility checks and activation timing, see the Japan eSIM FAQ.

How to choose when the network matters

1. List the places where losing data would cause a problem: a remote inn, a trailhead, a ferry port or a rural driving route.
2. Look those places up on each operator’s map.
3. Compare the result with the networks listed for the package you are considering.
4. Prefer a package that lists the network with coverage where you need it, or one that lists two networks.
5. Save offline maps and bookings anyway; no map is a guarantee.

If your trip includes Korea as well as Japan, the network question applies to both countries; our Japan and Korea eSIM guide covers that itinerary.

Frequently asked questions