Compare Unlimited eSIM Services for Japan: Best Options for Staying Connected

If you’re planning a trip to Japan or returning temporarily, how will you connect to the internet? Having a stable connection is very useful for searching tourist information, using map apps, and updating social media during your stay. One option that’s been getting a lot of attention recently is the eSIM. It’s convenient because you don’t need to physically insert a SIM card — you can buy and set it up online. However, even if a service says “unlimited,” there are some important things to be careful about. In this article, we’ll compare eSIM services in Japan that claim you can use data freely, and explain how to choose the right one.

About eSIMs That Let You Use Data Freely in Japan

When you hear “unlimited data,” you may think there are no speed limits no matter how much you use. But with many services — especially short-term prepaid types — it’s often not truly unlimited.

1-1. Do You Know About FUP?

“FUP” stands for “Fair Usage Policy.” It’s a rule to keep network quality stable so that one user’s heavy data use doesn’t affect others.

Even if the plan says “unlimited data,” if you go over a set amount of data per day or within a certain time, your speed may be heavily restricted. This is a FUP restriction. The limit (like 3GB per day or 60GB in 30 days) depends on the provider and the plan. It’s important to understand that “unlimited” doesn’t always mean truly unlimited.

1-2. Is 1GB Per Day Enough for You, or Do You Need More?

The best plan for you depends on how much data you’ll need during your stay in Japan.

• Just checking email, using maps, or light web browsing: In many cases, 1GB per day is enough. A plan with a FUP of over 1GB per day should work well.
• Watching videos, uploading lots of photos/videos, or tethering: These use a lot of data. You may need a plan with a loose FUP, or consider using multiple plans. Even if a plan says “unlimited,” FUP could cause restrictions quickly, so be careful.

Think about how you’ll use your phone and estimate the data you need. That will help you choose the right plan.

Comparison of eSIM Services That Offer Unlimited Data in Japan

Here we compare major eSIM services that offer “unlimited data” or something close. As mentioned earlier, many of these services do have FUP limits.

* Prices may change. Please check the official website for the latest info.
* The details of FUP vary by service. Be sure to read the terms and conditions of each provider.

As you can see in the table, each company offers different durations, prices, and FUP rules. For example, CDJapan Rental has 3GB/day, GigSky has 2.5GB/day, and Ubigi has 15GB for 7 days or 60GB for 30 days. Holafly and Sakura Mobile mention “unlimited” on their websites, but their provider KDDI actually enforces a FUP. Since the exact limits aren’t clear, please check their official websites.

Compare the plans based on how long you’ll stay in Japan, how much data you’ll need, and your budget.

docomo Has Stable Coverage Over a Wide Area

docomo’s network has wide and stable coverage all across Japan. KDDI is good for fast connections in cities and some areas. If you plan to travel around Japan, docomo is a good choice.

Buy Your eSIM Before Coming to Japan

The biggest benefit of eSIM is that you can buy and set it up online. Unlike physical SIM cards that you have to buy at the airport or in stores, it’s highly recommended to buy and set up your eSIM before departure. If you do it in advance, your phone will connect as soon as you land in Japan. That makes it easy to search transportation, contact your hotel, or communicate with others right away. Even if there’s a problem, you can use airport Wi-Fi to fix it before leaving your home country.

Important Things to Know When Using an eSIM in Japan

To use your eSIM smoothly, be sure to check the following before you come to Japan.

Check If Your Smartphone Supports eSIM

Make sure your smartphone supports eSIM and is unlocked.

• Check if it supports eSIM: Most newer smartphones support eSIM, but you should still check your device’s specifications.
• Check if it’s SIM-unlocked: If you bought your phone overseas or from a carrier, it may be locked. You must unlock it before using an eSIM. If it’s locked, it won’t recognize your eSIM.

How to check eSIM support on iPhone:

1. Open the phone app.
2. Enter “*#06#” and press call.
3. If you see “EID” on the screen along with other information like IMEI, then your phone supports eSIM.

For Android, you can usually check under “About phone” or “SIM status” in the settings.

3D Secure Authentication via Email

To buy an eSIM or make reservations and purchases in Japan (like Shinkansen tickets or event tickets), online credit card payment is often needed. In many cases, you’ll be asked for extra verification through “3D Secure.”

If your 3D Secure is set to use SMS to a mobile number that doesn't work in Japan, you won’t receive the code and won’t be able to complete the payment.

Before coming to Japan, check the 3D Secure settings for your credit card on your card provider’s website. If possible, change it from SMS to email authentication. That way, you can use online payment smoothly in Japan.

Summary

Having a good mobile connection is very important for a smooth stay in Japan. eSIMs are easy and convenient, but don’t just trust the word “unlimited” — check if there’s a FUP and what the limits are.

Choose the best eSIM plan based on how long you’ll stay and how you’ll use your phone. Prepare before you come, and enjoy a comfortable stay in Japan!