Distinguish Chinese and Japanese folk tunes in seconds, of course the video is an interpretation

The real reason is:

The correct tone of Chinese folk tunes is 12356

The correct tone of Japanese folk tunes is 67134

As for why there is such a difference, there is a rumor that needs to be verified. During the Kaiyuan period of the Tang Dynasty, when Jianzhen sailed to Japan, the humidity on the sea was too heavy and the guzheng was deformed by moisture, and 12356 became 13467, and it could not be restored to the correct tone. Later, this deformed tune formed a unique Japanese style.