In the Zenrin kokuhoki, a fifteenth century compilation of historical Japanese foreign relations, envoys from "Arabia" are mentioned in entries pertaining to Japanese diplomatic missions to China in the ninth century. Furthermore, a significant amount of Arabic traders were present in Chinese port cities during the 10th century. Thus, through various contacts with China, Japan would at least have been vaguely aware of lands as far west as the Middle East in the 8th-10th centuries, and presumably afterward.

Source: Von Verschuer; Japan's Foreign Relations 600 to 1200 A.D.: A Translation from Zenrin Kokuhοki; Monumenta Nipponica; 1999; 54(1).