Ubigi Review: Prices, Networks, Speed, 5G and Downsides
If you’re comparing eSIMs for a trip to Japan, Ubigi is likely to be one of the stronger options you come across.
In Japan, Ubigi can connect to KDDI (au) and NTT Docomo networks. It also supports 5G, tethering, and easy data top-ups. Once installed, the same Ubigi eSIM can also be reused on future trips abroad.
So, does that mean you can simply choose Ubigi and stop comparing? Not quite.
Ubigi is a well-balanced eSIM for many travelers, but there are several limitations worth knowing before you buy.
No Japanese phone number
No standard SMS service
Unlimited plans still have a full-speed data threshold
Real-world performance varies by location and conditions
Refunds are restrictive once you start using the data plan
In this review, we separate Ubigi’s official product information, independent Japanese mobile-network evidence, and practical considerations for traveling in Japan so you can decide whether Ubigi actually fits your trip.
Affiliate disclosure: Some links on this page are affiliate links. If you make a purchase through them, Project Torii may earn a commission at no extra cost to you. This does not affect our recommendations.
Contents
If You Want to Decide Before You Buy
1. Quick Answer | Is Ubigi a Good eSIM for Japan?
2. Ubigi in 30 Seconds | Key Facts
3. Ubigi Japan Plans and Prices
4. Which Ubigi Plan Should You Choose?
5. Is Unlimited Really Unlimited?
6. Japan Networks | KDDI (au) + NTT Docomo
7. Speed, 5G and Real-World Performance
8. What About Shinkansen and Regional Japan?
10. Does Ubigi Include Calls or SMS?
11. Who Is Ubigi Best For – and Who Should Skip It?
More Details Before and After You Buy
13. Can You Install Ubigi Before Flying to Japan?
14. What Happens If You Run Out of Data?
15. Can You Reuse the Ubigi eSIM on Your Next Trip?
16. What If Ubigi Does Not Connect in Japan?
1. Quick Answer | Is Ubigi a Good eSIM for Japan?
Project Torii Quick Verdict
Travel Match: 🟢 Strong Choice
Ubigi is especially worth considering if you:
Are visiting Japan for the first time
Are staying for around 7-14 days
Regularly use Google Maps, translation apps, web search and social media
Plan to visit regional Japan as well as Tokyo, Kyoto or Osaka
Care about the underlying Japanese network as well as price
May need to tether another device
If that sounds like your trip, Ubigi is a strong candidate.
→ Check Ubigi’s current Japan plans
Ubigi officially lists KDDI and NTT Docomo as its partner networks in Japan, with 5G support.
In Opensignal’s April 2026 Japan report, au won Reliability Experience and Consistent Quality outright, while NTT Docomo led Coverage Experience and 5G Coverage Experience.
In simple terms for travelers:
Network strengths
au → Reliability / Consistency
Docomo → Coverage
Access to two major Japanese networks with different strengths is one of Ubigi’s advantages.
If you are wondering, “What is the difference between Docomo, au and SoftBank anyway?” start here:
→ Docomo vs au vs SoftBank in Japan
However, Ubigi does not combine both networks at the same time.
Your phone connects to one available network, so actual performance can vary with location, time of day, congestion, device, and network selection.
It also does not mean an Ubigi user will always get exactly the same speeds as a direct au or Docomo subscriber.
If your itinerary is limited mainly to major cities such as Tokyo, Osaka and Kyoto, you probably do not need to overthink the network name. Price, data allowance, Unlimited conditions and ease of use may matter just as much.
We explain that distinction in more detail below.
Ubigi’s Main Strengths
Access to KDDI + NTT Docomo in Japan
5G support
Straightforward pricing
Tethering supported
Smartstart begins the validity period after you arrive
Easy data top-ups
Reusable eSIM for future trips
Ubigi’s Main Limitations
Data-only service
No Japanese phone number
No standard SMS
Unlimited plans have a Fair Use Policy
Performance varies by location and conditions
Refunds are generally difficult once usage has started
If you do not need a Japanese phone number and mainly want reliable access to Maps, translation and social media while traveling, Ubigi is an easy eSIM to shortlist.
2. Ubigi in 30 Seconds | Key Facts
| Item | Ubigi Japan |
|---|---|
| Service type | Data-only eSIM |
| Japan networks | KDDI / NTT Docomo |
| 5G | Supported |
| Tethering | Supported |
| Japanese phone number | No |
| Standard voice calls | No |
| SMS | No |
| WhatsApp / LINE etc. | Yes |
| Data top-ups | Yes |
| Smartstart | Yes |
| Reusable eSIM | Yes |
| Coverage | 200+ destinations |
Ubigi officially supports features including Smartstart, data sharing, top-ups, and reuse of the same eSIM across 200+ destinations.
3. Ubigi Japan Plans and Prices
Ubigi’s prices and plan lineup can change.
As of August 8, 2026, these are the main one-time (Ubigi calls them ‘one-off’) plans that are most relevant to travelers.
| Data | Validity | Price |
|---|---|---|
| 3GB | 15 days | US$7.50 |
| 10GB | 30 days | US$16.50 |
| 25GB | 30 days | US$32 |
| 50GB | 30 days | US$55 |
| Unlimited | 7 days | US$25 |
| Unlimited | 15 days | US$39 |
| Unlimited | 30 days | US$65 |
Ubigi also offers other options, including monthly and annual plans.
Because Project Torii mainly focuses on typical short- to medium-length trips to Japan, this review compares the one-time plans that are easiest for travelers to use.
Prices, allowances and promotions can change. Always check the latest terms before purchasing.
4. Which Ubigi Plan Should You Choose?
How much data you need depends not only on trip length, but also on how much you use social media, video and tethering.
As a practical planning baseline, Project Torii uses roughly the following allowances for a typical traveler.
| Trip length in Japan | Typical planning baseline |
|---|---|
| 5 days | About 3GB |
| 7 days | About 5GB |
| 10 days | 5-10GB |
| 14 days | About 10GB |
| 21 days | 10-20GB |
Applied to Ubigi, a simple way to think about the plans is:
Quick plan guide
Short trip / light use → 3GB
Typical 1-2-week trip → 10GB
Heavy social media, video or tethering → 25GB+
These are only general planning estimates.
→ See Ubigi’s latest Japan prices
If you spend a lot of time on Instagram or TikTok, watch YouTube while you are out, or tether a laptop, your data needs can be much higher.
On the other hand, if you use hotel Wi-Fi regularly and mainly rely on Maps, translation and messaging, you may need less.
Want a more precise answer to “How many GB do I need?”
→ How much data do you need for Japan?
5. Is Unlimited Really Unlimited?
Ubigi also sells Unlimited plans. But there is one important condition to understand before you buy.
Unlimited does not mean unlimited full-speed data.
Unlimited – 7 Days
US$25
Full-speed data: up to 25GB
After 25GB: 2Mbps
Unlimited – 15 Days
US$39
Full-speed data: up to 30GB
After 30GB: 2Mbps
Unlimited – 30 Days
US$65
Full-speed data: up to 60GB
After 60GB: 2Mbps
This is part of Ubigi’s Fair Use Policy.
At 2Mbps, you can still use messaging, email, Maps and light web browsing. It is much more limiting, however, if you want to keep streaming high-quality video or moving large amounts of data at full speed.
So Ubigi Unlimited does give you the reassurance that your connection can continue after you reach the full-speed threshold, but it does not mean unlimited high-speed data. Do not choose it based on the word ‘Unlimited’ alone.
6. Japan Networks | KDDI (au) + NTT Docomo
The underlying network is one important factor when evaluating Ubigi for Japan.
Ubigi officially lists KDDI and NTT Docomo as its networks in Japan.
In Opensignal’s April 2026 Japan report:
au / KDDI
Reliability Experience: outright winner
Consistent Quality: outright winner
Video Experience: outright winner
Also strong across several other experience metrics
NTT Docomo
Coverage Experience: outright winner
5G Coverage Experience: outright winner
The broadest geographic coverage among the Japanese operators in the report
Those results point to different strengths.
To make Japan’s major networks easier for travelers to understand, Project Torii summarizes them as:
Three-network shorthand
Docomo = Coverage
au = Reliability / Consistency
SoftBank = Download Speed / Urban Performance
This is not an absolute ranking. Network performance varies by place, time of day, congestion and other conditions.
For a trip focused only on major cities such as Tokyo, Osaka and Kyoto, all three major networks have extensive coverage, so the network alone usually should not decide your eSIM. The more your itinerary includes regional areas, suburbs, nature-heavy destinations or long-distance travel, the more useful the underlying network becomes as a comparison factor.
For a deeper comparison:
→ Docomo vs au vs SoftBank in Japan
7. Speed, 5G and Real-World Performance
Ubigi supports 5G in Japan, and its official Japan plans list KDDI and NTT Docomo as partner networks.
Project Torii does not give Ubigi a fixed speed figure such as “X Mbps.”
Actual eSIM speeds can vary with location, time of day, congestion, device, 4G/5G availability, the network you connect to, and roaming/routing configuration.
For context, Opensignal’s January-March 2026 measurements reported average Download Speed Experience of 60.7Mbps for au and 55.7Mbps for NTT Docomo.
Those figures measure the underlying au and NTT Docomo network experience. They are not direct speed tests of Ubigi users, and the distinction matters.
Project Torii therefore treats access to major Japanese networks as a positive, but does not claim that “Ubigi will give you X Mbps.”
8. What About Shinkansen and Regional Japan?
A Japan trip often involves more than Tokyo, Osaka and Kyoto. Connectivity also matters on Shinkansen trains, local trains, in regional cities, suburbs and mountainous areas.
On a Shinkansen, your phone is moving quickly between cell sites. Tunnels, mountainous terrain and congestion can also affect service, so any carrier can experience temporary slowdowns or unstable connections.
For that reason, we would not claim that “Ubigi is always perfect on the Shinkansen.”
On the other hand, NTT Docomo led Coverage Experience in Opensignal’s 2026 report, while au led Reliability Experience.
Project Torii therefore sees Ubigi’s available network combination as a positive factor for itineraries that include regional Japan or long-distance travel, not just major cities.
That does not mean you will have service everywhere, including every mountain area or remote island. If you already know your exact destinations, checking the official carrier coverage maps is the most reliable approach.
Project Torii Local Tip
Free onboard Wi-Fi is available on some Shinkansen services.
However, Project Torii does not recommend reducing your eSIM allowance because you expect to rely on Shinkansen Wi-Fi.
In our own use, it can be slow or unstable, particularly when trains are crowded.
Download video or music over hotel Wi-Fi in advance and treat Shinkansen Wi-Fi as a useful bonus when it works.
9. Can You Tether?
Yes.
Ubigi’s Japan one-time plans support data sharing/tethering.
You can temporarily share your connection with a laptop, tablet, another traveler’s phone, or a child’s device.
Any data used by tethered devices still comes out of your Ubigi allowance.
Laptops in particular can use unexpected amounts of data through cloud sync, operating-system updates, video streaming or large file transfers. Be careful with long tethering sessions if you are on a plan around 10GB.
10. Does Ubigi Include Calls or SMS?
Ubigi is a data-only eSIM.
It does not provide a Japanese phone number, and you cannot use the Ubigi line itself for standard voice calls or SMS.
You can still use data-based calling and messaging apps such as WhatsApp, LINE, FaceTime, Messenger and Skype.
On a Dual SIM phone, you can use Ubigi for mobile data in Japan while keeping your home SIM active for your usual phone number and SMS.
Charges for calls, SMS and international roaming on your home SIM depend on your home carrier and plan. In particular, make sure the home SIM does not use mobile data unintentionally.
For a typical sightseeing trip focused on Maps, translation, booking confirmations, messaging and social media, many travelers will be fine with a data-only eSIM.
11. Who Is Ubigi Best For – and Who Should Skip It?
Ubigi Is a Good Fit If You…
Are Visiting Japan for the First Time
It offers a good balance of pricing, network access, Smartstart and easy top-ups, without being overly complicated.
Are Taking a Typical 7-14 Day Trip
The 10GB / 30-day plan is an easy starting point for this type of trip.
Will Visit Regional Japan as Well as Major Cities
Access to both KDDI and NTT Docomo is a useful positive factor when comparing options.
Want to Tether
Data sharing is supported.
Travel Internationally More Than Once
You can keep the Ubigi eSIM installed and reuse it with a new plan on a future trip to a supported destination.
Ubigi May Not Be the Best Fit If You…
Need a Japanese Phone Number
Ubigi is data-only.
Need to Receive SMS on the Ubigi Line
The Ubigi line does not provide standard SMS service.
Want Truly Unlimited Full-Speed Data
Ubigi’s Unlimited plans still have a full-speed data threshold.
Have an eSIM-Incompatible or Carrier-Locked Phone
You will not be able to use the service.
→ Compare eSIM vs pocket Wi-Fi in Japan
12. Project Torii Verdict
Travel Match: 🟢 Strong Choice
Ubigi offers a strong balance of price, Japanese network access, 5G, tethering, Smartstart, top-ups and reusable eSIM support.
For a typical traveler visiting Japan for the first time, Project Torii considers Ubigi one of the stronger eSIM options.
For a typical one- to two-week trip, 10GB is a sensible place to start.
Access to KDDI (au) and NTT Docomo is another positive. Independent 2026 network evidence points to different strengths: au for Reliability / Consistency and NTT Docomo for Coverage.
If your trip is mainly in major cities, however, you do not need to choose Ubigi just because of the network names. Price, the amount of data you actually need, Unlimited conditions and ease of use should all be part of the decision.
A different option may make more sense if you need a phone number, need standard SMS on the travel eSIM itself, or expect to use very large amounts of full-speed data.
And like any mobile service, Ubigi can experience connection problems. “Strong Choice” does not mean a guarantee of perfect service everywhere in Japan.
Final Checks Before Choosing Ubigi
→ Docomo vs au vs SoftBank in Japan
→ How much data do you need for Japan?
→ Compare the best eSIMs for Japan
→ Check Ubigi’s latest plans and prices
Still Deciding? Compare Ubigi Side by Side
More Details Before and After You Buy
By this point, you should have the main information you need to decide whether Ubigi is right for your trip.
The sections below cover the smaller questions that often come up before or after purchase: when to install it, what happens if you run out of data, whether you can reuse the eSIM, what to try if it does not connect in Japan, iPhone settings, and refunds.
Use the contents above to jump directly to whichever section you need.
13. Can You Install Ubigi Before Flying to Japan?
Yes. In fact, setting it up before departure is usually the easier option.
Ubigi’s current one-time Japan plans support Smartstart.
You can install the eSIM before you leave, but the plan’s validity period begins when you arrive in a destination covered by the plan and connect to the supported network.
How it works
Before departure: Buy Ubigi → Install the eSIM
After arriving in Japan: Turn on the Ubigi line → Connect to a supported Japanese network → Plan validity begins
It is usually less stressful to prepare the eSIM before departure than to set it up for the first time after landing at the airport.
Smartstart plans expire if they are not activated within six months of purchase. That is unlikely to be an issue for normal trip planning, but there is also little reason to buy extremely far in advance.
14. What Happens If You Run Out of Data?
Ubigi supports top-ups.
You can buy a new data plan through the Ubigi app. Ubigi says you can top up in the app even if you have no Wi-Fi connection or remaining data allowance.
So you do not necessarily need to buy 50GB upfront just because you are worried about running out.
Example
Buy 10GB → Reach the second half of the trip with 1GB left → Top up only if needed
This makes Ubigi relatively flexible when you are not sure how much data you will actually use during your trip.
15. Can You Reuse the Ubigi eSIM on Your Next Trip?
Yes.
You can leave the Ubigi eSIM installed after your trip and buy a new plan when you travel to another supported destination.
Ubigi says the same eSIM can be used across 200+ destinations.
So there is no need to delete the Ubigi eSIM when your Japan trip ends. You can simply turn the line off while you are not using it and enable it again when you need it.
16. What If Ubigi Does Not Connect in Japan?
If Ubigi does not connect after you arrive in Japan, do not immediately assume the eSIM itself has failed.
Start by checking:
The Ubigi line is turned on
Ubigi is selected for cellular/mobile data
Data Roaming settings
Airplane Mode on/off
Restarting the phone
Network selection
APN settings
If necessary, you can also try selecting a network manually.
Because Ubigi uses KDDI and NTT Docomo in Japan, your phone may display the name of the local network you are connected to rather than ‘Ubigi.’
17. iPhone Settings to Check
If you use Ubigi alongside your home SIM on an iPhone, make sure your home SIM does not use mobile data unintentionally.
As a general rule, select Ubigi as the line for Cellular Data while you are in Japan.
Ubigi recommends keeping Allow Cellular Data Switching turned off.
If it is enabled, the iPhone may switch data back to your home SIM under some conditions, which can lead to international roaming charges.
Even if you keep your home SIM active for SMS or other purposes, pay close attention to its data-roaming settings.
18. What Is Ubigi’s Refund Policy?
Ubigi’s refund policy is worth checking before you buy.
For a preloaded eSIM purchased on Ubigi’s website, a refund may be possible only if none of the purchased data has been used.
Once you have started using the data plan, Ubigi says the refund request will be denied.
A refund may still be considered if you could not use the plan because your device was carrier-locked or incompatible.
A refund may also be available in some cases where a proven technical issue on Ubigi’s side prevented activation of the service.
Ubigi asks customers to contact support and provide proof of purchase within 14 business days of the purchase date or the date the technical issue occurred.
Before buying, confirm that your device supports eSIM and is carrier-unlocked.
19. FAQ
Can I Use Ubigi 5G in Japan?
Yes. Ubigi’s Japan plans list KDDI and NTT Docomo as supported networks and include 5G access. Actual 5G availability still depends on location, device and signal conditions.
Can I Make Phone Calls With Ubigi in Japan?
Ubigi is a data-only eSIM, so you cannot make standard voice calls on the Ubigi line itself. Internet-based calls through apps such as WhatsApp, LINE and FaceTime can still work.
Can Ubigi Receive SMS?
The Ubigi line does not provide standard SMS. If you need to keep receiving SMS on your home number, consider using a Dual SIM setup.
Can I Tether With Ubigi?
Yes. Ubigi’s Japan one-time plans support data sharing/tethering.
Can I Install Ubigi Before I Travel to Japan?
Yes. With a Smartstart plan, you can install the eSIM before departure and the validity period begins after you arrive in the covered destination and connect.
Is 10GB Enough for a Trip to Japan?
For many typical travelers, it can be. Project Torii uses about 5GB for 7 days and about 10GB for 14 days as practical planning baselines. Video, social media and tethering can increase your needs significantly.
→ How much data do you need for Japan?
Is Ubigi Unlimited Really Unlimited?
Your connection can continue after the full-speed allowance is used, but the plan has a Fair Use Policy. As of August 8, 2026, the 7-day Unlimited plan provides up to 25GB at full speed before dropping to 2Mbps, the 15-day plan provides up to 30GB before dropping to 2Mbps, and the 30-day plan provides up to 60GB before dropping to 2Mbps.
Does Ubigi Work on the Shinkansen?
It can, but high-speed travel, tunnels, mountainous areas and congestion can cause temporary instability on any network. Ubigi does not guarantee an uninterrupted connection throughout every Shinkansen journey.
Does Ubigi Work in Regional and Rural Japan?
Ubigi can connect to KDDI and NTT Docomo in Japan. NTT Docomo led Coverage Experience in Opensignal’s April 2026 report. That does not mean every mountain area or remote island is covered, so check official coverage maps if your itinerary includes specific remote destinations.
Should I Delete the Ubigi eSIM After My Trip?
If you may use Ubigi again, leave the eSIM installed and turn the line off instead. Ubigi says the same eSIM can be reused across 200+ destinations.
20. Sources & Evidence
Project Torii separates different types of evidence when reviewing eSIMs.
Official Product Information
For Ubigi’s product specifications, we prioritize information published directly by Ubigi.
We checked:
Prices
Data allowances
Validity periods
KDDI / NTT Docomo network support
5G
Smartstart
Data Sharing
Top-ups
eSIM reuse
Fair Use Policy
Calls and SMS
Refund Policy
The product information in this article was rechecked on August 8, 2026.
Prices, plans, partner networks and terms can change. Always confirm the latest details on Ubigi’s official website before purchasing.
Independent Network Evidence
For Japanese mobile-network performance, we use the Opensignal Japan Mobile Network Experience Report – April 2026.
Its data collection period was January 1 to March 31, 2026.
This report measures the experience of Japan’s mobile network operators. It is not a direct measurement of Ubigi users’ speeds, and Project Torii does not treat the two as the same thing.
Project Torii Local Experience
Comments in this article about Shinkansen travel and everyday connectivity in Japan are clearly separated as Project Torii’s local experience, not as official network-performance data.
We do not use one person’s experience alone to make broad claims that one carrier or eSIM service is universally better or worse.
Project Torii Editorial Note
Editorial Principle
Project Torii does not recommend an eSIM simply because it pays an affiliate commission.
We separate Official Information / Independent Evidence / Local Experience / Real-World Practicality / Price / Limitations wherever possible.
Our goal is not to sell the product with the highest commission. It is to help travelers decide which option actually fits their trip to Japan.
If Ubigi is not the right fit, we recommend choosing a different eSIM.
Source URLs | Editorial Reference
Ubigi Japan plans: https://cellulardata.ubigi.com/data-plans-and-coverage/ubigi-esim-data-plans/?one-off=on&monthly=on&annual=on&destination=jpn
Ubigi Help Center: https://cellulardata.ubigi.com/help-center/
Opensignal Japan Mobile Network Experience – April 2026: https://insights.opensignal.com/reports/2026/04/japan/mobile-network-experience