unrepatriated person
Refers to a person who has not been repatriated, especially in the context of post-war demobilization. This term is primarily historical and may appear in discussions of post-WWII Japanese soldiers or civilians stranded abroad.
Even after the war, there were people who were detained in Siberia as unrepatriated persons for a long time.
復員 refers to demobilization or repatriation itself, while 未復員者 specifically denotes a person who has not undergone that process.
未帰還者 is a broader term for someone who has not returned (e.g., from war or a mission), whereas 未復員者 is specifically tied to the formal demobilization process.
Compound of 未 (mi, 'not yet'), 復員 (fukuin, 'demobilization, repatriation'), and 者 (sha, 'person'). The term emerged in the post-WWII context to describe individuals awaiting official repatriation.