Every travel blog has a "best eSIM for Japan" ranking. Most are ordered by affiliate payout, not by what happens to your connection in a Kyoto subway. The factors that actually matter are unglamorous: which Japanese carrier network the eSIM rides on, whether tethering is allowed, and how "unlimited" is throttled.
The short answer
Decide in this order: 1) network (docomo/au/SoftBank) → 2) tethering policy → 3) data model (per-GB vs unlimited) → 4) support → 5) price. Price last, because a cheap eSIM that drops to 128kbps after your "fair use" quota is the most expensive mistake in Japan. Weigh these axes yourself in our Japan eSIM advisor — a transparent scoring engine, not a ranking we sell.
Why the network matters more than the brand
Travel eSIMs are resellers: your data rides one of Japan's three networks — NTT docomo (widest rural/subway coverage), au/KDDI, or SoftBank. Two eSIMs with the same price can behave completely differently because of this single fact. NTT-affiliated resellers (e.g. Ubigi by Transatel, an NTT company) and Japan-based providers (e.g. Sakura Mobile) typically ride docomo — the safe default for mixed city/countryside trips.
Quick comparison
| Provider | Type | Strength | Watch out |
|---|---|---|---|
| Ubigi | Global reseller (NTT group) | docomo network, solid quality | App-based top-ups |
| Sakura Mobile | Japan-based | English support from Japan, docomo | Not the cheapest |
| Airalo (Moshi Moshi) | Marketplace | Easy, instant QR, fair prices | Support is ticket-based |
| Holafly | Unlimited specialist | True set-and-forget data | Tethering restrictions — check current policy |
| Mobal | Japan/UK | Plans with a Japanese phone number | Overkill for short trips |
| Nomad | Marketplace | Aggressive pricing | Thin support |
Prices change weekly with promotions, so we deliberately score them as relative values with timestamps in the engine, and link to official pages for the live number. That is the honest way to compare.
Deeper: the three traps
Trap 1 — "Unlimited" with a fair-use clause. Many unlimited plans throttle after a daily threshold. If you upload video or navigate all day, read the fair-use policy before buying — the throttled speed (often 1Mbps or less) is what your worst day looks like.
Trap 2 — tethering. Some unlimited plans disable or cap hotspot use. If you work from a laptop, a per-GB plan with free tethering usually beats an unlimited plan with a hotspot ban.
Trap 3 — eKYC plans. eSIMs that include a Japanese phone number legally require identity verification (it is a Japanese telecom regulation, not the provider being difficult). Data-only eSIMs don't. For most tourists, data-only + a VoIP number is simpler.
Checklist before you fly
- Is your phone eSIM-capable and unlocked?
- iPhone XS or later, Pixel 3 or later, most recent Samsung flagships. Carrier-locked phones won't accept any eSIM. See what an eSIM is.
- Install before departure
- Buy and install the profile on hotel Wi-Fi at home; enable it when you land. Airport queues are for people with physical SIMs.
- Keep your home SIM for SMS
- Keep your primary line active (roaming off, line on) so bank verification SMS still arrives.
▶ Score Japan eSIMs with your own weights (network, tethering, price) — transparent engine