In the history of the relationship between Japan and China, those vessels were semi-official trading ships that likened to the period when relations worsened due to the Mongol invasion attempts against Japan (13th century) and the period when Japan and the Ming dynasty in China started trade (15th century).
日中関係史において、元寇による関係悪化（13世紀）と日明貿易（15世紀）の間の時期をつなぐ、半官半民的な交易船である。