From Nothing to Envy: Ordinary Lives in North Korea, by Barbara Demick (Spiegel & Grau, 2009), Kindle Loc. 534-548:
In fact, Japanese Koreans, who were known as kitachosenjin, after the Japanese term for North Korea, Kita Chosen, lived in a world apart. They had distinctive accents and tended to marry one another. Although they were far from rich by Japanese standards, they were wealthy compared with ordinary North Koreans. They had arrived in the new country with leather shoes and nice woolen sweaters, while North Koreans wore canvas on their feet and shiny polyester. Their relatives regularly sent them Japanese yen, which could be used in special hard-currency shops to buy appliances. Some had even brought over automobiles, although soon enough they would break down for lack of spare parts and have to be donated to the North Korean government. Years after they arrived, Japanese Koreans received regular visits from their relatives who would travel over on the Mangyongbong-92 ferry with money and gifts. The ferry was operated by the pro-regime Chosen Soren and its visits to North Korea were encouraged as a way of bringing currency into the country. The regime skimmed off a portion of the money sent by relatives. Yet for all their wealth, the Japanese Koreans occupied a lowly position in the North Korean hierarchy. No matter that they were avowed Communists who gave up comfortable lives in Japan, they were lumped in with the hostile class. The regime couldn’t trust anyone with money who wasn’t a member of the Workers’ Party. They were among the few North Koreans permitted to have contact with the outside, and that in itself made them unreliable; the strength of the regime came from its ability to isolate its own citizens completely.
The new immigrants from Japan quickly shed their idealism. Some of the early immigrants who arrived in North Korea wrote letters home warning others not to come, but those letters were intercepted and destroyed. Many of the Japanese Koreans, including some prominent in Chosen Soren, ended up being purged in the early 1970s, the leaders executed, their families sent to the gulag.