study/academic, 20.2% for other reasons and 0.2% unknown. The survey excluded those who were under 12 when they arrived in Japan. Pre-modern era While some families today can ultimately trace their ancestry to Korean immigrants, they were absorbed into Japanese society and are not considered a distinct group. The same is applicable to those families descended from Koreans who entered Japan in subsequent pre-modern periods. Trade with Korea continued to modern times, with Japan also periodically receiving missions from Korea, though this activity was often limited to specific ports. Yayoi period In late prehistory, in the Iron Age Yayoi period (300 BC to 300 AD), Japanese culture some Korean influence, though whether this was accompanied by immigration from Korea is debated (see Origin of the Yayoi people). Kofun period (250 to 538) In the later Kofun (250–538) and Asuka (538–710) periods there was some flow of people from the Korean Peninsula, both as immigrants and long-term visitors, notably a number of clans in the Kofun period (see Kofun period#Korean migration). While some families today can ultimately trace their ancestry to the immigrants, they were absorbed into Japanese society and are not considered a distinct group. Heian period (794 to 1185) In the records from Nihon Kōki, in the year 814, six people, including a Silla man called Karanunofurui (Korean: 가라포고이, Japanese: 加羅布古伊; presumed to be of gaya descent) became naturalized in Japan's Minokuni (美濃國) region. Sengoku period (1467 to 1615) Some Koreans entered Japan in captivity as a result of pirate raids or during the 1592-1598 Japanese invasions of Korea. Edo period (1603 to 1867) In the Edo period, trade with Korea occurred through the Tsushima-Fuchū Domain in Kyūshū, near Nagasaki. Before World War II After the conclusion of the Japan-Korea Treaty of 1876, Korean students and asylum seekers started to come to Japan, including Bak Yeonghyo, Kim Ok-gyun, and Song Byeong-jun. There were about 800 Koreans living in Japan before Japan annexed Korea. In 1910, as the result of the Japan–Korea Annexation Treaty, Japan annexed Korea and all Korean people became part of the nation of the Empire of Japan by law and received Japanese citizenship. In the 1920s, the demand for labor in Japan was high while Koreans had difficulty finding jobs in the Korean peninsula. Thousands of Koreans migrated or were recruited to work in industries like coal mining. A majority of the immigrants consisted of farmers