Answer: {Hello Kirito here! Hope that this helps.}
The founding legend of Gojoseon, which is recorded in the Samguk Yusa (1281) and other medieval Korean books, states that the country was established in 2333 BC by Dangun, said to be descended from heaven.
So, the very first Korean (s) was, Siberia/Manchuria or Dangun
Step-by-step explanation: