Complex sentence: Immigrants to Japan may have included privileged classes, such as experienced officials and excellent technicians who were hired in the Japanese court, and were included in the official rank system which had been introduced by the immigrants themselves.
Split into simpler sentences: Immigrants to Japan included the privileged classes, such as experienced officials and excellent technicians. Many of them were hired in the Japanese court, and were included in the official rank system which had been introduced by the immigrants themselves.