Looking to stay connected while traveling in Japan? Consider au KDDI, one of Japan’s major carriers known for wide 4G coverage and affordable tourist rates. Their prepaid SIM cards and eSIM plans provide reliable connectivity throughout your trip. This guide summarizes your au by KDDI options for easy mobile access during your time in Japan.

au by kddi sim card

1. Quick Facts about au KDDI

au by KDDI has a long history of connecting Japan through innovative communications. Formed in 2000 when KDD, IDO, and DDI joined together, KDDI Corporation now provides popular mobile, internet, and home phone services under the au brand.

  • au by KDDI is a Japanese mobile phone operator, the second-largest in the country with over 60 million subscribers.
  • It is a brand marketed by KDDI, a telecommunications company that also provides fixed-line phone, internet, and TV services.
  • au offers a variety of mobile phone plans, including data plans, voice plans, and combination plans.
  • It is known for its high-speed data network and its wide range of handset choices.
  • au also offers a variety of other services, such as music streaming, video streaming, and mobile payments.
au kddi logo

2. Why au by KDDI When You’re Exploring Japan – Coverage and Speed

Whether you’re in major cities or remote towns, au aims to keep you connected with wide-ranging 4G coverage and fast LTE speeds across the country.

2.1. au by KDDI Coverage in Japan

Japan Mobile Operators Coverage
Japan Mobile Operators Coverage

According to an April 2023 Opensignal report:

  • au’s 5G coverage score was 4.3/10, meaning 5G is visible in about half of locations visited by au users. While improvement is needed, AU is expanding its 5G coverage.
  • Au has extensive 4G and 3G coverage nationwide from over 20 years of operation. KDDI’s 4G network reaches 99% of Japan’s population, on par with SoftBank and Docomo.

Strong 4G signals can be expected in major cities, towns, and rural areas, as well as along highways, bullet trains, and subways. Au provides excellent nationwide coverage for tourists, with occasional gaps in remote mountains.

2. au KDDI Speed

Opensignal april 2023 download speed Japan au kddi

In terms of mobile data speed, OpenSignal’s 2023 testing found AU achieved an average 4G download speeds of 44.53Mbps in Japan. This is comparable to SoftBank (41.78Mbps) and slightly faster than Docomo (39.56Mbps).

Real-world speeds will be dependent on location, network congestion, devices, and other factors. But you can generally expect fast enough speeds for GPS, social media, video calls, and light media streaming. While not the blazing-fast 5G speeds, au’s 4G network is reliable for everyday mobile usage as a traveler.

3. au by KDDI Connectivity Options for Travelers to Japan

KDDI offers travelers to Japan two main options for staying connected while abroad – pocket Wi-Fi routers and prepaid data SIM cards.

au kddi wifi connection

Pocket Wi-Fi routers can be rented from KDDI stores located at major airports and cities across the country. They provide portable Wi-Fi hotspots that work on KDDI’s cellular network. Prepaid data SIM cards are also available for purchase at KDDI stores. These SIMs allow you to insert them into an unlocked smartphone or tablet for cellular data access.

The following table provides an overview of the key pros and cons of each option to consider when deciding what best fits your connectivity needs:

Connectivity Options KDDI Rental Wi-Fi Router KDDI Prepaid Data SIM Card
Coverage Connects to cellular network for coverage anywhere within range of au signal. Coverage depends on unlocked device's network bands matching au frequencies.
Ease of Use No need to swap SIMs- device automatically connects to router Wi-Fi. May need to ensure device is unlocked and SIM card is installed properly.
Cost Higher upfront cost but includes all you can use data for rental period. Lower upfront cost but must purchase data in pre-determined amounts.
Data Allowance Unlimited data for rental period (usually 500MB/day or higher). Data packages of 1-2GB per day available, with overage charges.
Device Compatibility Compatible with any Wi-Fi enabled device. Only compatible with unlocked smartphones/tablets that support au frequencies.
Mobility Router can be taken anywhere for coverage, but is a separate device. Built-in cellular connectivity on a single mobile device.
Security Public Wi-Fi hotspot could pose security risks. Potentially more secure than public Wi-Fi as a mobile signal.

4. Best au Japan SIM Cards for Tourists & Cost

Starting in November 2018, au KDDI stopped accepting new prepaid phone signups in Japan. If your prepaid card expires, you cannot renew. Luckily, MVNOs offer prepaid alternatives on KDDI’s network for short-term visitors without contracts:

KDDI Plans

Provider Data plans Data Charge Charge (in $US) English Support
Mineo Data Only 5GB 1265 yen 8.48 No
Data Only 10GB 1705 yen 11.43
Data Only 20GB 1925 yen 12.91
Nuro VS Plan 3GB 627 yen 4.20 No
VM Plan 5GB 825 yen 5.53
VL Plan 10GB 1320 yen 8.85

The MVNO rents space on the major networks at a lower cost, passing the savings to customers. So whether you’re here a week or a month, MVNOs let you easily keep in touch without all the red tape of a postpaid account. Something to consider if au prepaid isn’t feasible anymore during your stay.

5. Does au KDDI Support eSIM in Japan?

No, AU does not offer eSIM plans for travelers, only for residents. An eSIM allows mobile data activation directly on compatible phones without a plastic SIM.

If you’re looking for a different choice using the au mobile network, esimjapan.net also provides some fairly convenient travel eSIM options you could consider.

6. Where Can You Buy an au Japan SIM Card and eSIM?

Whether you’re traveling to Japan for work or pleasure, being able to connect to WiFi on the go is essential. Learn where you can buy an au Japan SIM card or eSIM.

6.1. Where to Buy au Japan SIM Cards

You can purchase au Japan SIM cards at:

  • au Stores: au retail shops are found in most cities and airports. Find your closest AU store location using the store locator search tool.
  • Airport Kiosks: Look for au partner kiosks at Narita, Haneda, Osaka Kansai airports
  • Convenience Stores: Bic Camera, Yodobashi Camera, and Yamada Denki often sell au SIMs
au japan physical store
  • Online Purchase: Visit the au KDDI online shop website. Log in with your AU ID for security. Your ID must be linked to an active AU or UQ Mobile account. Select the desired prepaid au Japan SIM card and follow the activation instructions included.
how to buy au japan sim card online

When buying in person, you may need your passport to register the SIM card. Online purchases will be shipped to your hotel or pick-up location.

We've researched the places that sell SIM cards at Japan Airports, so you don't have to. Check out our comprehensive guide: 

6.2. Where to Buy au by KDDI eSIM in Japan?

Here are some options for buying an AU by KDDI eSIM in Japan:

  • Bic Camera/Yodobashi Camera electronics stores: Major consumer electronics chains Bic Camera and Yodobashi Camera sell au eSIM packages in their stores. Staff can assist with activation.
  • Supermarkets/convenience stores: AU partners with larger supermarkets like Aeon and convenience stores like Lawson to sell eSIM starter packs. Look in the telecom sections.
  • Third-party retailers: Small phone shops and online retailers such as esimjapan.net carry au eSIM packages imported directly from KDDI. Activation support varies.

So in summary, the most digital-friendly options are purchasing directly from au’s online store, or via third-party providers like esimjapan that can deliver the eSIM profile via email before your trip.

esimjapan.net offers the best local eSIM plans starting at just $5

7. How to Activate au Japan SIM Card/ eSIM in Japan?

Whether you’re traveling to Japan short-term or living there long-term, having a Japanese SIM card provides important connectivity. This article explains the simple process for activating an au Japan SIM card or eSIM so you can enjoy mobile service on your device while in the country.

7.1. How to Use au by KDDI SIM Card in Japan?

Here are the simple steps to activate your new AU prepaid SIM card:

  1. Purchase the SIM card package from any AU store. It will have an activation code.
  2. Insert the SIM into your unlocked phone and turn it on.
  3. Activate by dialing *149# and following the voice prompts. You can choose your language here.
  4. When asked, enter the long activation code from the package. Press to confirm.
  5. You’ll hear your new balance and use time. Congrats, your SIM is now ready to use!

7.2. How to Activate au by KDDI eSIM?

Getting your KDDI eSIM set up for travel in Japan is simple with these steps:

  • Purchase the perfect KDDI eSIM plan from esimjapan.net based on your trip length in the land of the rising sun.
  • Download the eSIM profile to your device the day before your Japan adventure begins. That way you’ll be all set to go once you touch down.
  • With a strong wifi connection, download the eSIM profile so you can access the internet during setup.
  • Open the email from esimjapan.net and copy over the all-important activation info like ICCID and code.
  • Insert the eSIM using the QR scan or manual entry of those ID numbers.

Follow the on-screen prompts to activate it with a quick setup process and you’re now free to roam around Japan without any physical SIM switching headaches. If questions come up, the esimjapan.net support squad is there to help you out.

8. au by KDDI Japan Call and SMS Rates

Even prepaid SIM cards include unlimited domestic calling and texting. International calls and texts will be charged separately:

Rate Detail Charge Charge (USD/min)
Calling Rate Weekday Daytime (8:00-19:00) ¥10/6 seconds $0.12/min
Weekend/Holiday Daytime (8:00-23:00) ¥10/6 seconds $0.12/min
Weekday Night (19:00-23:00) ¥10/5.5 seconds $0.10/min
Late Night/Early Morning (23:00-8:00) ¥10/5.5 seconds $0.10/min
SMS Rate within Japan ¥5.14 per message $0.06/message
International Call Rate Calls to USA ¥20/12 seconds $0.20/min
Calls to South Korea ¥20/9 seconds $0.15/min
Calls to China/Taiwan ¥20/8 seconds $0.13/min
Calls to UK, Germany, France ¥20/6 seconds $0.10/min

So you can stay in touch with contacts in Japan without worrying about call or text charges. Just budget separately if planning international usage.

9. Useful USSD Codes for au KDDI SIM/eSIM

You can check your AU SIM card balance and info by dialing these shortcodes:

Dial Purpose
157 Access prepaid phone services
1140 Register prepaid card
1142 Check balance and remaining usage days
1143 Select a foreign language for voice guidance
0077-7-111 Contact au customer center for inquiries about mobile services
0077-7084 Contact au customer center for inquiries about contracts, fees or billing
0077-777 Contact au customer center for inquiries about connection settings or failures

These shortcodes provide an easy way to quickly pull up your account status and balances when needed.

10. How to Top-up au KDDI SIM/eSIM

There are several ways to top up your au KDDI prepaid SIM card depending on your location and preference:

  • au Shops: Visit any au shop and tell the staff you want to top up your prepaid SIM card. You can pay with cash, credit card, or au PAY.
  • Convenience Stores: Most convenience stores in Japan, such as FamilyMart, Lawson, and 7-Eleven, offer top-up services for AU prepaid SIM cards. You can usually purchase top-up vouchers with different denominations and use them to top up your SIM card online or through the My au app.
  • ATM Machines: Select ATMs, particularly those of au partner banks like Mitsubishi UFJ Bank and Bank of Yokohama, allow you to top up your au prepaid SIM card directly.
  • Online: You can top up your au prepaid SIM card online through the My au website or app. You can pay with a credit card or au PAY.

11. FAQs about au KDDI Mobile in Japan

Does au KDDI SIM work for international roaming outside Japan?

No, au prepaid SIMs can only be used domestically within Japan. For any travel outside Japan, you would need to get a local SIM card in that country.

Can I use au KDDI SIM in my non-Japanese phone?

Yes, au SIM cards are compatible with unlocked phones. iPhones and smartphones from the US, Europe, or Asia should work fine. You may need to adjust cellular/data settings.

Is there an expiration date for unused au Japan SIM card credits?

Yes, the data and validity allotted with your au prepaid SIM expire at the end of the stated 7/14/30 day period. Any unused data does not roll over after expiry.

How can I track my data usage on au Japan SIM card?

You can check your remaining data balance using the *135# USSD code or in the au prepaid app. This lets you monitor usage to avoid surprise overage charges.

Does AU Japan SIM card work for 5G or only 4G LTE?

au’s prepaid SIMs are currently 4G LTE only. 5G service is only offered on postpaid plans. But the 4G speeds should suffice for most visitor usage.

12. Final Words

In summary, au KDDI offers reliable connectivity options for travelers in Japan. Their prepaid SIM cards and eSIM plans provide widespread coverage and fast speeds at affordable prices. An eSIM plan is very convenient if your device supports it. Otherwise, AU’s physical SIM cards are easy to purchase and activate. With their services, you can stay connected across Japan with a suitable solution from au.