Are the Japanese descendants of Jiaodong people?

First of all, not all Japanese are descendants of immigrants from ancient China. Secondly, even the descendants of immigrants from China are mainly descendants of people in coastal areas of wuyue and Fujian.

Jiaodong area, that is, Guqi people, is a major immigrant input area on the Korean Peninsula. It is the ancestral home of many Koreans. In addition, in the Tang Dynasty, Jiaodong was also one of the two main areas where Koguryo people were resettled in the later Tang Dynasty. So some people in Jiaodong area (especially Denglin) are descendants of Koguryo people.