Japan's mobile networks compared: docomo, au (KDDI), SoftBank, Rakuten, IIJ

The operators

• NTT docomo

  Own network. 3G (FOMA) ended on 31 March 2026; it now runs 4G and 5G.

• au (KDDI)

  Own network. 3G has ended; it now runs 4G and 5G.

• SoftBank

  Own network. 3G ended in April 2024 (July in Ishikawa); it now runs 4G and 5G.

• Rakuten Mobile

  Where its own network doesn't reach, it uses au's.

• IIJ

  No towers of its own; it runs on docomo's or au's network.

What independent tests found

The two main testers disagree. Opensignal's April 2026 Japan report (January to March data) gave au the most awards and NTT docomo the top coverage experience score. Ookla's first-half 2026 report found SoftBank had the fastest median download and NTT docomo the highest share of time on 5G.

These figures are for local subscribers. A travel eSIM uses the same towers, but its speed and 5G access depend on the plan's roaming terms, so it won't match a local SIM exactly.

One network or several

A plan on one network depends entirely on that network's signal. A plan that lists two or more connects to whichever has signal, so pick one of those for Hokkaido, the Okinawa islands, the mountains or ski areas.

Each plan's networks are listed under “Available networks” on the Japan eSIM page, which also shows how many plans use each operator.

A Japanese network doesn't mean a Japanese IP

Many travel eSIMs route traffic back through Hong Kong, Singapore or elsewhere before it reaches the internet, and that is where sites and apps think you are. Academic measurements have found that a travel eSIM's exit often differs from both where it was issued and where it's used.

The “IP exit” in each plan's details shows where it exits; if it's missing, the supplier hasn't stated one. For services that only work from Japan, choose a plan marked Japan.