How to Choose the Best eSIM for Japan
byCharles McQuainJapan is one of the most connected countries in the world — but choosing the right eSIM takes a bit of research. Most tourist eSIM plans route through one of Japan's three major carriers: NTT Docomo, SoftBank, or KDDI. Which carrier your eSIM uses matters more here than in most countries. Docomo has the widest nationwide reach, including rural coverage and most subway tunnels. SoftBank has strong urban density in Tokyo and Osaka. During rush hour in packed areas like Shinjuku or Shibuya, speeds on any network can dip — that's normal across all providers.
If coverage is your top priority, Ubigi stands out from the pack. Ubigi is owned by NTT — the parent company of NTT Docomo, Japan's largest carrier — and its Japan plans list all three major networks: KDDI, NTT Docomo, and SoftBank. Popular alternatives like Saily and Nomad use KDDI and SoftBank. You can't choose which network you land on, but whether you're hiking in Nikko, catching the shinkansen through the Japanese Alps, or navigating backstreet Osaka, having Docomo in the mix gives Ubigi more to fall back on. And it isn't a premium buy: Ubigi's 10 GB / 30-day plan is $16.50, versus $18 on Airalo and $17.99 on Saily.
For most travelers, the decision comes down to data volume and cost. A 3–5 GB plan covers a week of maps, messaging, and social media. Go 10–20 GB if you're streaming, working remotely, or doing heavy Google Maps navigation. One underestimated data hog: real-time camera translation apps (like Google Translate's camera mode) burn through data fast — budget an extra 2–3 GB if you plan to use them extensively throughout the trip.
Why Ubigi Has the Best Coverage in Japan
Ubigi is owned by NTT, the parent company of NTT Docomo — Japan's #1 network by coverage area — and Ubigi's Japan plans list Docomo alongside KDDI and SoftBank. Popular alternatives like Saily and Nomad use KDDI and SoftBank. You can't choose which network you land on, but having Docomo among the options helps with rural coverage and connectivity in Tokyo subway tunnels. If you're heading anywhere outside major city centers, or just want the most reliable signal possible, Ubigi is the one to pick.
Why trust this comparison?
We compare 14 providers for Japan using published plan data and real-world testing. Affiliate commissions keep AvailSim free but never influence rankings. Read our methodology