How does Unicom number send short messages to China's short message platform in Japan?

Before going to Japan, you need to open the international roaming function. After going to Japan, you can send short messages to domestic mobile phone users and directly enter their mobile phone numbers. For sending short messages to international users: 00+ country code+user number (for example, sending short messages "8765432 10" to American users), users enter "+18765432 1065438" or "0876543265438" on their mobile phones.