Chinese historian often viewed their neighbor states as backward and less cultured, that doesn't mean they are not aware of the fact that those so-called less cultured people had their own countries.

Written Chinese historical record showed that they know about the Gojoseon kingdom in present day North Korea dated as far as 7th century BC. Shima Qian's Shi Ji wrote about 箕子, who was said to rule Gojoseon kingdom in 12th century BC. Those account may be somewhat inaccurate, but there is no doubt that Chinese historian knew for sure that there was a kingdom there. China was also aware of Japan, Han emperor sent a golden seal to Japanese ruler in the 1st century. This is a practice between China and its tributaries to announce that the Emperor acknowledge the right to rule of the king of that tributary state.