Man'yōgana is the oldest known sound-based writing system used for the Japanese language. When kanji, or Chinese characters used to write Japanese, first came to Japan in around the 4th century AD through the Korean Peninsula, it was only used to write the Chinese language. Even though Chinese was not native to the Japanese people, classical Chinese writings were nonetheless studied heavily by upper-class Japanese. Some time later, although the exact time is unknown, Chinese characters, which came be known as kanji in Japan, was being used to write the Japanese language for the first time in roughly the 6th century AD, although it had a heavy Chinese influence.