Are Korean immigrants in China during the Warring States Period a thing of the past?

No, Korea in the Spring and Autumn Period and the Warring States Period is in Shanxi today.

Now Koreans are Koreans, close to Wuhuan in Liaodong, or some descendants of Wuhuan, and basically belong to a single nation, Koreans.

The main source of the Korean nation should be the earliest resident of the Korean peninsula-Han filth. Their ancestors lived on the Korean peninsula as early as the Paleolithic Age. Koreans belong to the southern Mongolian race and live in the southern part of the Korean peninsula. The filth people belong to the northern Mongolian race, living in the northern part of the Korean Peninsula and the northeastern part of China. Korea and Fei have a large population for a long time, and they are the epitome of Paleolithic and Neolithic cultures on the Korean peninsula.