Comparing Prepaid SIMs in Japan: Data-Capped Plans vs. Unlimited Plans

What is a Prepaid SIM?

A prepaid SIM is a SIM card that allows you to use a certain amount of data for a specific period on a pay-as-you-go basis.

With no binding contract periods and no strict identity verification procedures requiring a residence card, they are the perfect option for foreign tourists on short-term stays.

Basic Features of a Prepaid SIM

• Pre-payment System: You pay the fee before use, so there are no worries about additional charges.
• Limited Duration: Most are valid for a fixed period, such as 3 to 180 days.
• Capped/Uncapped Data: There are "data-capped plans" with a limit on data usage and "unlimited plans" without one.
• Simple Procedures: In most cases, they can be purchased with just a passport, eliminating complex contract procedures.
• Immediate Use: You can start using it right after purchase with a simple setup.

Differences from Standard Contract SIM Cards

Compared to a regular mobile phone contract (postpaid), prepaid SIMs have the following differences.

Features of Prepaid SIM in Japan

Prepaid SIMs offered in Japan have several unique characteristics.

Network Quality and Speed

Prepaid SIMs in Japan are primarily provided by MVNOs (Mobile Virtual Network Operators) that lease networks from major carriers (docomo, au, SoftBank).

Because of this, you can expect stable network quality nationwide.

While high-speed communication is generally not an issue in urban areas, the connection may become unstable in some areas like mountainous regions or remote islands.

Carrier Support and Compatibility

To use a prepaid SIM in Japan, you need a device that is SIM-unlocked (SIM-free).

In recent years, many smartphones are sold as SIM-free, reducing compatibility issues, but it's always best to confirm that your device is SIM-unlocked before purchasing.

Data-Only or With Voice Calls

There are mainly two types of prepaid SIMs:

• Data-Only: Allows only internet connection.
• With Voice Calls: Allows calls and SMS in addition to internet connection.

Most foreign tourists choose data-only SIM cards.

This is because they can make calls using apps like LINE and WhatsApp.

However, if you need a local Japanese phone number during your stay, you should consider a SIM with voice call functionality.

Features and Recommendations for Data-Capped Plans

A data-capped plan is a plan that allows high-speed communication up to a predetermined data limit, after which the speed is restricted.

Pros of Data-Capped Plans

• Clear Pricing: The amount of data available for a fixed price is clear.
• Cost-Effective: Cheaper than unlimited plans if your usage is low.
• Variety of Plan Options: You can choose from various data allowances like 3GB, 5GB, 10GB, etc.

Cons of Data-Capped Plans

• Risk of Exceeding the Cap: If you exceed the set limit, your speed will be throttled (to around 128kbps–1Mbps).
• May Require Top-Ups: You might need to pay extra to add more data if you run out.
• Potential for Wasted Data: If your usage is low, you might not use up the data you paid for.

Recommended Data-Capped Plan

GTN Prepaid SIM

Overview in 30 seconds

GTN Prepaid SIM is a prepaid SIM for short to medium-term visitors, offering data-only plans for a minimum of 7 days to a maximum of 90 days, and voice + data plans that allow immediate acquisition of a Japanese phone number.

Not sold at convenience stores

Available for purchase at:

• Web application (home delivery / eSIM)
• GTN directly managed stores (Tokyo - Shin-Okubo / Osaka)
• Chubu Centrair International Airport Station Meitetsu Travel Plaza
• GTN Korea Seoul Branch

Application possible with passport only

• No residency period conditions, available for foreign visitors to Japan

Customer support in 13 languages

• Including Japanese, English, Chinese, Korean, Vietnamese, Indonesian, Nepali, Mongolian, etc.

*Data-only eSIM also supports online applications before arriving in Japan.

運営会社	Global Trust Networks Co., Ltd.
料金	Pricing & Plans Data-Only SIM / eSIM For those prioritizing internet connectivity for streaming, navigation, and social media. Data Capacity Duration Price (Tax Incl.) 30 GB 7 Days ¥3,000 10 GB 30 Days ¥3,000 50 GB 30 Days ¥5,000 135 GB 90 Days ¥10,000 Voice + Data SIM Ideal for those who need a local phone number for calls and SMS authentication. Data Capacity 30-Day Plan 90-Day Plan 5 GB ¥6,500 ¥15,980 15 GB ¥9,500 ¥22,980 25 GB ¥12,500 ¥28,980 Note on Voice Plans: > * Domestic Calls: ¥22 per 30 seconds. SMS (Domestic): ¥3.3 to ¥33 per message. Additional charges apply for these services. Information as of February 2026.
公式HP	https://www.gtn-mobile.com/

Four Features

Flexible Plan Structure Supporting Short to Medium Term Stays 

Data-only plans are available for 7 to 90 days, and Voice + Data plans for 30 to 90 days. You can choose a plan that matches your stay duration, from a one-week business trip to a three-month medium-term stay.

Application Possible with Just One Passport 

No credit card, bank account, or residence card is required. There are no restrictions based on the period of stay, so it can be used by foreign visitors to Japan, short-term visitors, and foreign residents in Japan.

Multilingual Customer Support 

Supports languages including Japanese, English, Chinese, Korean, Vietnamese, Indonesian, Nepali, and Mongolian. Even those who are not confident in Japanese can consult in their native language.

Supports Online Application Before Arriving in Japan (Data-only eSIM) 

Data-only eSIM plans allow online application and activation preparation before arriving in Japan. You can secure communication from the moment you arrive at the airport.

Recommended Plans by Use Case

Where to Purchase

Features and Recommendations for Unlimited Plans

An unlimited plan is a plan that allows you to use data without worrying about the amount, or one that offers a very large data allowance.

Pros of Unlimited Plans

• Peace of Mind: Use data without worrying about the consumption.
• Enjoy Video Streaming: Watch high-volume content like YouTube and Netflix without hesitation.
• Tethering with Multiple Devices: Feel secure sharing your connection with multiple devices like laptops and tablets.

Cons of Unlimited Plans

• Higher Price: Tends to be more expensive than data-capped plans.
• Fair Use Policy: Even "completely unlimited" plans may have speed restrictions for extremely heavy usage.
• Short-Term Only: Many unlimited plans are for short periods, often 30 days or less.

Cautions for Unlimited Plans

Even if advertised as "unlimited," all plans may have the following restrictions:

• 3-Day Total Limit: Many "unlimited" plans have a limit, such as 10GB over 3 days.
• Speed Throttling: Connection speed may decrease during peak hours.
• Daily Cap: Some plans may have a daily data usage limit.
• Fair Use Policy: Extremely high data consumption may be restricted.

How to Choose a Plan

To choose the best prepaid SIM, consider the following points.

Choosing Based on Length of Stay

Choosing Based on Usage Purpose

How to Choose Cost-Effectively

• Know your typical usage: Use your monthly data consumption in your home country as a reference.
• Consider special usage patterns during travel: Frequent use of map apps, increased photo uploads, etc.
• Possibility of using Wi-Fi spots: Time spent in places with Wi-Fi, like hotels and cafes.
• Sharing with multiple people: A large-capacity plan is advantageous if you plan to share the connection with family or friends via tethering.

How and Where to Buy

Prepaid SIMs can be purchased in various places. Here are the features and methods for each.

Buying at the Airport

Pros

• Get it immediately upon arrival.
• Choose from multiple types.
• Staff support is often available.

Main Sales Locations

• Narita International Airport: Various locations in the arrival lobbies (Terminals 1, 2, & 3).
• Haneda Airport: International Terminal arrival lobby.
• Kansai International Airport: Arrival lobby.
• Chubu Centrair International Airport: Arrival lobby.
• Fukuoka Airport: International Terminal.

Sales Hours

• Counters: Generally from around 7:00 to 22:00.
• Vending Machines: Available 24 hours (at some airports).

Buying at Convenience Stores

Pros

• Easy to find anywhere in the country.
• Many locations are open 24 hours.
• Often does not require passport presentation.

Main Sales Locations

• Lawson: Japan Travel SIM, etc.
• 7-Eleven: Various prepaid SIMs.
• FamilyMart: Various prepaid SIMs.

Purchase Steps

1. Select the product from the prepaid SIM section in the store.
2. Pay at the register.
3. Receive it on the spot.

Buying at Electronics Stores

Pros

• Wide variety to choose from.
• Can get advice from staff.
• Can purchase along with a device.

Main Sales Locations

• Bic Camera
• Yodobashi Camera
• Yamada Denki
• Edion

Buying Online

Pros

• Can prepare in advance (order before arriving in Japan).
• Easy to compare prices.
• Airport pickup may be available.

Main Sales Sites

• Amazon.co.jp
• Rakuten Ichiba
• Official websites of each prepaid SIM provider.
• Travel service sites like Klook and KKday.

Purchase Steps

1. Order and pay online.
2. Specify delivery to your accommodation or pickup at the airport.
3. Receive it at the designated location.

Buying an eSIM

The number of eSIMs, which do not require a physical SIM card, is increasing.

Pros

• No need to swap physical SIM cards.
• Can be issued instantly online.
• Can be set up before arriving in Japan.

Main Providers:

• IIJmio (Japan Travel SIM eSIM)
• Mobile-router.com
• Airalo
• Ubigi

Cautions:

• Requires an eSIM-compatible device.
• The setup method is different from a traditional SIM.

Setup and Activation Steps

Once you have purchased a prepaid SIM, follow these steps to set it up.

Basic Setup Steps

Insert the SIM card into your device

• Turn off your device.
• Eject the SIM tray (using the dedicated pin).
• Set the SIM card according to its size.
• Re-insert the SIM tray.
• Turn on your device.
•  

Configure the APN settings

For iPhone:

• Settings > Cellular > Cellular Data Network
• Enter the required information (APN, Username, Password).

For Android:

• Settings > Network & internet > Mobile network > Access Point Names
• Add a new APN and enter the necessary information.

Check the connection

• Turn on mobile data.
• Confirm your internet connection.
• Check the connection speed with a speed test app.

Points to Note During Use

• How to check data usage: Can be checked on the provider's website or app.
• What to do when speed is limited: Top up with additional data or continue using at the throttled speed.
• Contact for troubleshooting: Each company's customer support (check for multilingual support).
• What to do if lost: Re-issuance is generally not possible, so be careful.

Frequently Asked Questions

Q1: Is identity verification required for a prepaid SIM?

A: For data-only prepaid SIMs, you can often purchase them by just showing your passport. For SIMs with voice call functionality, identity verification is required by law.

Q2: What happens if I use up all my data?

A: With a data-capped plan, your connection speed will be restricted (typically to 128kbps–1Mbps) once you use up your data. Some plans allow you to purchase additional data.

Q3: Can I use it all over Japan?

A: Since they use the networks of major carriers, they can be used in most areas across Japan. However, the connection may be unstable in some areas like mountainous regions or remote islands.

Q4: Can I use it with a smartphone from another country?

A: If your device is SIM-unlocked (SIM-free), it will most likely work. However, you should pay attention to the supported frequency bands of your device.

Q5: Is tethering possible?

A: Most prepaid SIMs support tethering (sharing the connection with other devices), but some providers may have restrictions. Please check the product description.

Q6: What happens to the data I didn't use within the validity period?

A: Generally, any remaining data will expire once the validity period is over. Some plans may allow for an extension of the period.

Q7: Will I get a phone number?

A: Data-only prepaid SIMs do not come with a phone number. If you choose a prepaid SIM with voice call functionality, you will be assigned a Japanese phone number.

Q8: What is an eSIM? What's the difference from a physical SIM?

A: An eSIM does not require a physical SIM card; you can download the SIM information digitally using a QR code. It requires an eSIM-compatible device.

Summary

Prepaid SIMs in Japan come in data-capped and unlimited plans, each with its own characteristics. To choose the best plan, keep the following points in mind.

Pros of Data-Capped Plans

• Relatively inexpensive.
• Allows you to choose a plan based on your usage.
• Ideal for short-term stays.

Pros of Unlimited Plans

• Peace of mind without worrying about data limits.
• Freedom to watch videos and use tethering.
• Suitable for sharing with multiple people.

Final Points for Choosing a Plan

• Length of Stay: Data-capped for short stays, large-capacity or unlimited for long stays.
• Usage Purpose: Small capacity for just SNS and maps; large capacity for video streaming and tethering.
• Budget: Consider the balance between price and data allowance.
• Ease of Access: Buy at the airport if you want to use it immediately upon arrival.
• Multilingual Support: Choosing a product with language support provides peace of mind.

Setting up your internet environment in Japan will make your travel and stay more comfortable. Choose the prepaid SIM that fits your needs and enjoy your time in Japan to the fullest.