All the Japanese officers in "Bright Sword" are played by China people? What about the Japanese line?

This is mainly achieved through post dubbing.

Dubbing is the process of adding sound to movies or multimedia. In a narrow sense, dubbing refers to: the voice actor dubs the role (in the play) or replaces the language dialogue of the role in the original film with other languages.

Sometimes, because there are mistakes and omissions in the voice in the original play, the process of restoring the dialogue for the segment by the original actor is also called dubbing. When recording a photographic work, the voice of the actor or singing voice is replaced by others, which is also called "dubbing".

In a word, dubbing is a language art, and it is the creative work of the dubbing actor to shape and perfect various vivid and colorful characters with his own voice and language behind the screen and in front of the microphone.