The Human Condition I: No Greater Love (1959)

A Japanese pacifist, unable to face the dire consequences of conscientious objection, is transformed by his attempts to compromise with the demands of war-time Japan.

During World War II, a Japanese man accepts to work as supervisor in iron ore mine in Manchuria to avoid to be summoned to the military service and fight as Japanese soldier.
He witnesses the oppression Chinese mine workers go through everyday. They are considered war prisoners and live in a war camp.

if you check The Human Condition trilogy movie

you can feel my way Korean movie story somewhat based on it in simple and short way