1: Click the input method in the lower right corner-select the language preference.
2. Then set Microsoft Chinese as the default language.
3: Shut down and restart to see if it is back to normal.
If not, you should delete Japanese first.
Then turn it off, turn it on, and add it.
Changing the language in WIN 10 can sometimes be strange. Once I changed it to English, and then I changed it back to Chinese, where I started some Chinese and some English. Be sure to delete the added language first, then close and open it again, and then add it.