Japan opens doors to mass immigration

[PSOL]

"Immediately following the end of World War II, there were roughly 2.4 million Koreans in Japan; the majority repatriated to their ancestral homes in the southern half of the Korean Peninsula"



https://books.google.com./books?id=ZUVGAQAAQBAJ&pg=PP1&redir_esc=y#v=onepage&q&f=false

From that, an estimated 900k are descendants of the Zainichi Koreans who stayed. That doesn’t exclude those who have Korean ancestry for several centuries due to cross movement, including the royal family.