Yes. You can receive Taiwan SMS messages (including verification codes) for free while in Japan.

📌 Explanation:
• Taiwan mobile numbers (such as Chunghwa Telecom / Taiwan Mobile) can still receive SMS messages while you are in Japan.
• Even without applying for international roaming, SMS reception usually works as long as the SIM card remains active.
• Receiving SMS messages generally does not incur any charges (actual conditions may vary depending on your mobile carrier).

📌 Dual SIM Settings (for both Android and iPhone):
• Keep both your original SIM (Taiwan number) and JB SIM enabled at the same time.
• For calls and SMS, we recommend keeping your original SIM (SIM1).
• Switch mobile data to the JB SIM (SIM2) for internet access.
• The same settings apply when using eSIM, allowing both SIMs to be used simultaneously.

📌 Recommendation:
• Switch mobile data to the JB SIM after arriving in Japan.
• This helps prevent accidental roaming charges from using mobile data on your original SIM.