Two recent events suggest that the Northern Japanese may have had some sort of trade relations with Koreans as early as the stone age, and that they have pronounced several kanji characters similarly. Archaeologists have discovered a couple of stone tools with a tanged point resembling a hunting knife used some 20,000 to 25,000 years ago, one in the Kaminoa ruins in Shinjo, Yamagata Prefecture, and the other at the Jingeuneul site near Gwangju, South Korea.
Similarly, researchers in Tokyo, working with their Korean counterparts, discovered kanji characters, believed to have been unique to Japan, written on an old wooden plate were also found in wooden strips in South Korea. Many other similar tools have been found mostly in Kyushu, the main Japanese island nearest the Korean Peninsula. Some believed that this was because Kyushu was much closer to Korea in ancient times than it is now. While Masao Anbiru, professor of East Asia in the Old Stone Age at Meiji University, believes that big numbers of Koreans might have migrated to Japan, Toshio Yanagida, director at the Tohoku University Museum, said that while the tanged points do not make that direct conclusion, they at least show that there was some sort of exchanges made between the two.
Meanwhile, researchers at the National Museum of Japanese History in Tokyo showed that letters on wooden strips found in South Korea indicated that Baekje, a kingdom that existed from the fourth to the seventh century, had a similar arrangement to Japan in terms of charging interest payments for rice loans. Also appearing in a wooden plate dating to mid-seventh century Baekje is the kanji “ru,” pronounced similarly in Japan and ancient Korea. “The same kanji was assigned the same sound because Japan and Baekje might have shared part of their cultures,” according to Minami Hirakawa, director-general at the Museum.