My grandfather went to Manchuria during the Japanese occupation where there were many Koreans that had left the peninsula. He started a business, but when it didn’t go well, he set sail for Japan. When Korea was liberated, he moved his family back to Gyeongsang-do Province where he had been born.
My father-in-law was also born in Japan. My father and father-in-law discovered at the sanggyeonnye, or formal meeting between two families before a wedding, that they were the same age and given the period they were born into, had childhood histories that followed similar trajectories. They were both born in Japan into families that had gone there to find work, and returned to Korea and settled down after liberation.
In the early 20th century, hundreds of thousands left the Korean peninsula and went to Manchuria or Japan. My father and father-in-law returned to Korea, but far more people remained. If the grandfathers of me or my wife had not returned, we’d be referred to as joseonjok (descendants of Koreans in China) or jaeil gyopo (descendants of Koreans in Japan) today.