🅰️The prepaid card uses a 4G/LTE mobile network, and docomo has the most base stations in Japan, offering the widest coverage. Please refer to the comparison table below.
When you go to areas outside major cities in Japan, you will notice a significant difference.
Regular maintenance hours (Japan Time)
Every Tuesday from 10:00 PM to Wednesday 9:00 AM
■eSIM
During the system maintenance period, issuing eSIM activation QR codes will not be possible.
If the “Issue” button has already been pressed, the status will remain as “Pending.”
You may exit the screen and return later via the link to check the issuance result.
If the activation code has already been issued, you can still proceed with “Add eSIM” and begin using the service, even during maintenance.
■SIM Card
Inserting a physical SIM card into a smartphone or other device during the maintenance period may result in no response.
However, there is no need to worry — the system will automatically complete the activation process in order once maintenance is finished.
SIM cards that are already in use will not be affected.
■Voice SIM Card
Voice SIM cards are pre-activated before delivery and are therefore not affected by system maintenance.
Temporary Maintenance hours (Japan Time)
① Sep. 24, 2025, 10:00 PM ～ Sep. 25, 2025, 9:00 AM
■Functions Temporarily Unavailable
■Notes
The signal strength is mainly affected by the telecommunications company’s network infrastructure. The factors that influence the signal strength are as follows:
The distance to the base station
Presence of obstacles
Presence of signal interference
Antenna performance
Frequency band Since our company’s eSIM and SIM cards are products from Japan’s local docomo telecom company, using the same signal, the speed of our eSIM and SIM cards are the same. As for other international roaming eSIMs, there may be cases where roaming is done through smaller telecom companies, leading to significant differences in speed and coverage.
「settings」➔「General」➔「About」➔「Carrier Lock」 ➔No SIM restrictions
You cannot determine this directly from the mobile phone. Please check with the place of purchase or the carrier you have a contract with.
SIM lock regulations vary by country. In Taiwan, most phones are not SIM-locked.Devices purchased in countries like Japan or the United States are more likely to have SIM lock issues.
📢If you have used SIM cards from different countries or carriers, the device is likely not SIM-locked.
Taiwan’s major mobile carriers provide Wi-Fi Calling services.
➡ While you are in Japan, Wi-Fi Calling is treated as if you were using your phone in Taiwan.
📲 Receiving calls and SMS: Free
📲 Making calls and sending SMS: Charged at your Taiwan domestic rates
・Your phone is connected to Wi-Fi.
・Wi-Fi Calling is enabled on your phone (please refer to the attached guide).
・Your Taiwan SIM card is active.
(No international roaming subscription is required, so you don’t need to worry about additional roaming charges.)
Calling a Taiwan number
➡ Dial the Taiwan phone number directly without adding the country code.
Calling a Japan number
➡ Make an international call.
(Example: 009-81-…)
・No need to enable international roaming.
・You can make and receive calls over Wi-Fi even in areas with poor mobile signal, such as indoors.
・The person you’re calling will not know that you’re overseas.
・You can also receive SMS verification codes while abroad.
Yes, you can use this service if the following conditions are met:
✅ Your smartphone is connected to Wi-Fi
✅ The Wi-Fi Calling function is enabled
✅ You are using a supported device (iPhone / Android)
✅ Your SIM card remains active (not suspended or cancelled)
📞 Making calls
・Calling a Taiwan number → Taiwan domestic call charges
・Calling a Taiwan mobile number → Taiwan domestic rates
・Calling overseas (e.g., Japan) → International call charges
👉 No international roaming charges will apply
📲 Receiving calls
・Receiving calls from Taiwan → Free (same as receiving calls in Taiwan)
