Origins of the Japanese (reference)

The history of the Japanese relies on the Korean (c. 7th Century CE) and the Chinese (c. 2nd and 3rd Century BCE) records.

However, written Japanese records come later than 612 CE, and paints a mythological history with occasional facts included.

Before the 3rd century BCE, "Shan Hai Jing", the Book or Classics of Mountains and Seas, compiled as 18 chapters from the original records of 32 chapters by Liu Xiang and Lin Xin at the end of the Western Han Dynasty under the Han imperial order, recorded the existence of Wo [Wa] Japan as known in prehistoric China.

Shan Hai Jing 12 states that "Wo (Wa in Japanese) was subject to the Yan statelet of the Zhou Dynasty" which means that "the ancient Wo Japanese travelled through the peninsula to submit tributes to Yan in today's Peking area."

During the 7th Century BCE when Yan moved its capital "from Liulihe to that of Ji, in modern-day, Xicheng District of Beijing".

Thus the Yan statelet of the Zhou Dynasty had made trade ties with the Wa Japanese after its capitol moved to Ji.

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Reference

Origins of the Japanese: http://www.imperialchina.org/Japanese.shtml
Yan (state): http://en.wikipedia.org/wiki/Yan_(state)