Traveling to Japan, is there a signal from Unicom's mobile phone number to Japan?

Unicom's mobile phone number can only be used if the international roaming or international long distance function is enabled.

Pre-paid users do not need to apply, and international roaming services in Hong Kong, Macao, Taiwan, Malaysia, South Korea, Vietnam and other regions and countries are opened by default. Post-paid users can log in to Unicom's online business hall, click "Business Handling" > "International Business" > "International Roaming in Taiwan, Hong Kong and Macao", open or cancel international roaming rights and choose to order superimposed packages.