au (KDDI) in Japan: Coverage & Tips for Travellers
eSIM from 1,00 USD · 100 MB. Networks: KDDI/au (5G), NTT docomo (4G), NTT docomo (5G), Rakuten Mobile (5G), SoftBank (5G).
au (KDDI) in Japan
Best for: Balance of speed and coverage
What to know
- Good nationwide reach and competitive in cities
- Strong in western Japan (Kansai, Kyushu)
Areas where signal can drop
- Deep mountain areas (Nikko and Hakone lake districts)
- Remote islands (Yakushima, Iriomote in Okinawa)
- Some train tunnels on scenic rural lines
- Basement floors of dense Tokyo electronics districts
Other carriers in Japan
- NTT Docomo: Widest coverage including rural Japan
- SoftBank: Urban speeds and 5G
If you have no signal (quick troubleshooting)
- Aeroplane mode for 10 s → disable.
- Confirm the eSIM line is set as "Mobile Data".
- Restart your phone.
- Settings → Network → Manual network selection → choose au (KDDI).
- If nothing works: check the APN (sometimes needs manual configuration).