MyJapan+ eSIM half-price offer is limited to Taiwan travelers

August 25, 2026. JCB and KDDI are offering four discounted povo Japan SIM data periods inside the MyJapan+ by JCB app until September 30. The prices start at ¥330 for 24 hours and rise to ¥1,695 for seven days.

The offer sounds open to international visitors, but the purchase route is much narrower. A customer needs a Taiwan phone number that can receive the verification message and a JCB card issued in Taiwan. The service works only in Japan and does not include a telephone number, calls or SMS.

The traveler decision: MyJapan+ is a strong short-trip price for an eligible Taiwan traveler who wants unlimited-period data on KDDI's au network. A Roaming eSIM is the more accessible choice for travelers without the required Taiwan number and card, for trips longer than seven days, or for itineraries continuing beyond Japan.

What the MyJapan+ eSIM offer includes

The June 25 launch notice lists four Japan-only data periods. KDDI describes them as unlimited, with possible speed restriction during network congestion and for data-heavy uses such as video streaming or cloud gaming.

These are tax-inclusive launch figures. KDDI's current contract schedule contains later pricing and bundle arrangements, so the live MyJapan+ purchase screen should control after September 30 rather than the older “reference price” column being treated as a permanent tariff.

Japan SIM uses KDDI's au network and supports 5G where the device, network and location allow it. It is a best-effort mobile service, not a guaranteed speed. “Unlimited” describes the lack of a stated fixed gigabyte cap during the purchased period; it does not promise an unchanging download rate at a packed station or while streaming.

Taiwan eligibility is the main MyJapan+ restriction

The registration steps require both of these:

• a Taiwan phone number for SMS verification;
• a JCB-branded credit card issued in Taiwan.

The Japan SIM base-plan terms make the JCB-app route specific to Taiwan. Holding a JCB card issued in another country does not satisfy the published payment condition. Having a Taiwan card without an SMS-verifiable Taiwan number does not complete the stated registration path either.

The account holder must be at least 18. KDDI says photo ID is not required for this route, but that does not remove the phone and payment checks. One Japan SIM account accepts one Taiwan phone number.

Check before downloading the app: “for international visitors” describes who will use Japan SIM in Japan. It does not mean every visitor can buy through MyJapan+.

Buying during sign-up changes when the unlimited period starts

This is the detail most launch stories omit.

The current MyJapan+ offer page says data validity normally begins immediately after purchase. When an eligible plan is bought as part of the initial sign-up, however, the unlimited period is supplied as a promo code. The traveler can apply that code after arriving in Japan.

KDDI's data-topping terms describe the first-purchase bundle as 0.5GB valid for 60 days plus the chosen unlimited period. The practical sequence is:

1. Register through MyJapan+ with the eligible Taiwan number and card.
2. Install the Japan SIM profile while reliable internet is available.
3. Keep the promo code somewhere accessible outside the eSIM profile.
4. After arriving in Japan, connect over Wi-Fi if needed and apply the code when ready to start the unlimited period.
5. Confirm the expiry shown in the account rather than calculating it from the flight time alone.

A later add-on bought outside the sign-up bundle can start immediately. Do not buy another short period early unless the order screen clearly shows when its clock begins.

The 24-hour option is not the same as one calendar day

The plan names use hours and days, but the account expiry remains the authority. A 24-hour topping is designed as a continuous duration after application, while the three-, five- and seven-day offers follow the product's stated validity.

Travelers should leave enough time for the final airport transfer. Starting a seven-day code immediately after a morning arrival can leave no coverage for an evening departure more than seven days later. A short extension, hotel Wi-Fi or another plan may be needed.

If several data add-ons are active, KDDI says the one expiring first is consumed first. Buying another pack does not extend an existing expiry; concurrent clocks continue to run.

What happens after the MyJapan+ data period ends

Without an active topping, Japan SIM is limited to a maximum of 128kbps. That can be enough for a small message under good conditions, but it should not be treated as dependable navigation, ticket retrieval or a fresh plan-purchase connection.

Save these before the paid period ends:

• the hotel address in Japanese;
• airport or station directions;
• ticket and reservation QR codes;
• the MyJapan+ login and promo-code record;
• a payment method and support details;
• an offline map of the next route.

The Japan SIM account automatically becomes inactive 90 days after the eSIM is enabled, whether or not another add-on was purchased. It is not presented as a lifetime profile for future annual trips.

Calls, SMS, hotspot and support limits

Japan SIM for MyJapan+ is data-only. It does not provide normal voice calls, SMS or mobile number portability. App calls and messages can use the data connection, but a hotel landline, restaurant telephone booking or SMS verification still needs another service.

Keep the Taiwan or home line active if incoming messages are important, and check its roaming charges. On a compatible dual-SIM phone, select Japan SIM for mobile data and disable cellular-data switching if the phone might fall back to the home line. Our calls and SMS guide explains the distinction.

The checked MyJapan+ offer page does not publish a clear hotspot allowance. Do not assume that “unlimited” also means unrestricted laptop or group tethering. Ask povo support before purchase if hotspot use is essential.

All registration and support are online. The published support window is 9:00 a.m. to 7:00 p.m. Japan Standard Time, in English. That is narrower than round-the-clock support, so install before departure and avoid leaving an unfamiliar setup until late at night in Japan.

No refunds, returns or eSIM reissues

KDDI's MyJapan+ terms state there are no returns, refunds or reissues. A partial refund is not available when a traveler leaves early or uses only part of a period. Deleting the profile, choosing the wrong device or discovering a lock after purchase can therefore be costly.

Before paying:

1. Confirm the phone supports eSIM and is carrier-unlocked.
2. Update the operating system while still on trusted Wi-Fi.
3. Check that the Taiwan number can receive the verification message.
4. Confirm the card was issued as a JCB card in Taiwan.
5. Install on the phone that will be carried to Japan.
6. Save the order, promo code and support route separately.

Use our phone compatibility guide and installation timing guide before committing.

MyJapan+ eSIM versus Roaming eSIM for Japan

MyJapan+ wins a narrow, valuable use case: an eligible Taiwan traveler needing a short unlimited period on the au network before September 30. Roaming eSIM is easier to access and compare across a wider range of travelers and trip shapes.

🏆 Roaming eSIM wins on access and trip choice: it does not require a Taiwan-issued JCB card, and its live catalog lets a traveler compare Japan-only, Japan–South Korea, Asia and global coverage. MyJapan+ wins the current short-duration price decision for a traveler who meets every eligibility rule and accepts the activation and support limits.

Current Roaming eSIM alternatives for Japan

At 10:43 UTC on August 25, the public Roaming eSIM catalog returned 43 Japan packages starting at US$0.60. The results carried KDDI, NTT Docomo, Rakuten and SoftBank operator labels across available cards; 40 packages were marked top-up eligible. These are changing inventory fields, not a guarantee that every plan uses every listed operator or can be reloaded.

The Japan Roaming eSIM guide covers setup, transport apps and country-plan choices in more detail.

Ten questions travelers ask about MyJapan+ and Japan eSIMs

Can any visitor to Japan buy the MyJapan+ eSIM?

No. The published route requires an SMS-verifiable Taiwan phone number and a JCB card issued in Taiwan.

Can I use a JCB card issued outside Taiwan?

Not under the current MyJapan+ payment rule. The official terms specify a JCB-branded credit card issued in Taiwan.

When does the MyJapan+ unlimited data start?

An eligible period bought during sign-up is delivered as a promo code that can be applied in Japan. Other purchased toppings can begin immediately, so read the exact order screen.

Is the MyJapan+ eSIM really unlimited?

KDDI does not state a fixed gigabyte cap for the listed period, but it may restrict speed during congestion or data-heavy activity such as streaming and cloud gaming.

Does it work outside Japan?

No. Japan SIM for MyJapan+ is valid only in Japan.

Does it include a Japanese phone number, calls or SMS?

No. It is a data-only service without normal calls, SMS or MNP.

Can I share MyJapan+ data by hotspot?

The checked offer page does not state a clear tethering allowance. Confirm with povo support before purchase if sharing is required.

What speed remains after the topping expires?

KDDI lists a maximum of 128kbps without an active data topping. Prepare offline essentials before the paid period ends.

Can I get a refund or move the profile if I make a mistake?

The published terms say no returns, refunds or reissues. Confirm the unlocked compatible device before payment and do not delete the profile casually.

Is MyJapan+ or Roaming eSIM better for Japan?

MyJapan+ is compelling for an eligible short visit during the discount. Roaming eSIM fits more travelers, longer or multi-country routes, and buyers who want package fields and a 24/7 support route before choosing.

Sources and updates

The launch date, four promotional prices, September 30 deadline, Taiwan phone and JCB-card conditions, au network and congestion note come from KDDI and povo. The current MyJapan+ offer page and KDDI contract documents supplied the promo-code timing, 0.5GB first-purchase bundle, concurrent expiry, 128kbps fallback, age, online support hours, Japan-only scope, data-only limit, 90-day account closure and no-refund or reissue terms.

Most repeat the four launch prices.

Update this page when the September 30 campaign ends or KDDI changes the eligible phone numbers, payment cards, prices, promo-code delivery, data periods, network, speed policy, calls, SMS, hotspot, support, refund, reissue or account-lifetime terms.