noun
Often used for a foreigner of European ancestry; can sound old-fashioned or literary in modern Japanese. 外国人 is the neutral modern term.
明治時代、異人たちが横浜に多く住んでいた。
In the Meiji era, many foreigners lived in Yokohama.
noun
different person; another person
Used to emphasize that someone is a different individual, not the same person. Often appears in contrastive contexts.
彼は以前とはまるで異人のようだ。
He seems like a completely different person from before.