KDDI (au) is one of the networks your eSIM may use in Japan. Here is who actually decides which network you get, and what to do with that.
Quick answer
KDDI (au) is a mobile network operator in Japan, and one of the networks a travel eSIM may reach through roaming. From the information we track, it runs 4G and 5G.
From the supplier record behind each package, 88 of the 100 plans we currently sell for Japan declare KDDI (au) as a network the profile can reach, at 4G and 5G. The figure comes from the same catalogue that prices the plan pages, not from marketing copy, and it moves when the supplier revises the record.
Nearly every travel eSIM is a roaming product. The supplier holds agreements with one or more networks in the destination, and your profile picks between them by a priority order set inside the profile, not by the buyer. Two travellers on the same plan can end up on different networks in the same city.
| What decides the network you get | Who controls it |
|---|---|
| The supplier's roaming agreements | The plan's supplier |
| The priority list inside the profile | The plan's supplier |
| The bands your handset supports | Your device |
| Signal strength where you stand | Physical location |
| How congested the cell is right now | The local network |
This describes how roaming works in general; it does not cite any specific commercial agreement.
Alongside KDDI (au), the market also has NTT DOCOMO, Rakuten Mobile, SoftBank, any of which your plan may use depending on the supplier.
88 of our plans name KDDI (au) as reachable, but that is not a guarantee. Not necessarily. Travel plans run over roaming agreements, so the network depends on the supplier behind the plan, your device and where you are. KDDI (au) is one of the networks operating in Japan, not a guarantee attached to any particular plan.
Check the carrier name at the top of the screen, or open the mobile-network settings and look at the operator list. If signal is poor, try selecting a network manually instead of automatic — but only one your plan actually supports.
From the operator information we track, KDDI (au) runs 4G and 5G. Getting 5G in practice needs three things at once: the plan permits it, your device supports it, and the area has coverage. Miss any one and you fall back to 4G.
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Ranked by our value score. Each plan page lists the networks its supplier declares.
NTT docomo / Rakuten Mobile / KDDI/au
Exits in Hong Kong · NTT docomo / Rakuten Mobile / KDDI/au
Tempoh sah laku bermula pada sambungan pertama di destinasi
NTT docomo / Rakuten Mobile / KDDI/au
Exits in Hong Kong · NTT docomo / Rakuten Mobile / KDDI/au
Tempoh sah laku bermula pada sambungan pertama di destinasi
KDDI/au
Exits in Singapore · KDDI/au
Tempoh sah laku bermula pada sambungan pertama di destinasi
NTT docomo / Rakuten Mobile / KDDI/au
Exits in Hong Kong · NTT docomo / Rakuten Mobile / KDDI/au
Tempoh sah laku bermula pada sambungan pertama di destinasi
KDDI/au
Exits in Singapore · KDDI/au
Tempoh sah laku bermula pada sambungan pertama di destinasi
NTT docomo / Rakuten Mobile / KDDI/au
Exits in Hong Kong · NTT docomo / Rakuten Mobile / KDDI/au
Tempoh sah laku bermula pada sambungan pertama di destinasi
