Complex sentence: The overall Japanese Brazilian population is declining, secondary to a decreased birth rate and an aging population; return immigration to Japan, as well as intermarriage with other races and dilution of ethnic identitySignificant populations of Chinese and Koreans also live in the district of Liberdade.
Split into simpler sentences: The overall Japanese Brazilian population is declining, secondary to a decreased birth rate and an aging population; return immigration to Japan, as well as intermarriage with other races and dilution of ethnic identity. However, significant populations of Chinese and Koreans also live in the district of Liberdade.