There are two theories. First, the Japanese Tianzhi Emperor nine years (Goguryeo reported that the King of the first year, the first year of Tang Xianheng, Meng Gaozu twenty-two years; Silla Wenwu Wang ten years; 670 years), Tianzhi Emperor Tianmai Kai別 change the name of the country to Japan. New Book of Tang - East Barbarians biography: "Xianheng first year, sent to He Ping Goryeo. Later, he learned the sound of Xia and changed his name to Japan. The envoys said that they thought of Japan because of its name. Some said that Japan was a small country, which was annexed by the Japanese, so they took its name. The envoys were not in favor of the name, so they were suspicious of it." Second, after Zetian, Wuju ordered the Japanese to change their name to Japan. Zhang Shoujie's "Justice in the Records of the Grand Historian" has the phrase "Empress Wu changed the name of the Japanese state to Japan". The Classic of Mountains and Seas: "Beyond the East China Sea, in Penglai Pavilion, there is the wood of Fusang, and the wood is born on the tenth day of the sun. Japan means the wood of the sun, the origin of the sunrise

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