There’s definitely a lack of evidence when it comes to the origins of the Japanese language. But, there are a few theories on how the language of Japan came to be. One of these theories is the migration of the Yayoi people from Korea to Japan 2-3000 years ago. Or the language could have originated from the Jomon people already living in the area. But, there’s no way to tell how these languages related to modern Japanese, because they weren’t written down.