Windows 10 uses a default character set called "Code Page 1252" for displaying file names in File Explorer. However, Japanese characters are not included in this character set. This means that if you have files with Japanese characters in their names, File Explorer may not be able to display them properly.

Solution : Change the System Locale

One solution to this issue is to change the system locale to Japanese. This will change the default character set used by Windows 10 to display file names in File Explorer. Here's how to do it:

1. Open the Control Panel.
2. Click on "Clock and Region."
3. Click on "Region."
4. Click on the "Administrative" tab.
5. Click on "Change system locale."
6. Select "Japanese (Japan)" from the list.
7. Click on "OK."
8. Restart your computer.