Documentary evidence attesting to Japanese control of Ezochi under the bakuhan system state is provided by a vermillion-seal certificate issued by Toyotomi Hideyoshi in 1593, a black-seal certificate issued by Tokugawa Ieyasu in 1604 and vermillion-seal certificate issued by second Tokugawa Hidetada and his successors (with the exception of the seventh Takogawa Ietsugu and the fifteenth Takugawa Yoshinobu) in the 1970’s studies utilizing these documents shed light on the establishment of Matsumae and on the relationship between Ezochi and the system. But these studies were restricted in scope in that there were conducted within a framework restricted in its term of reference to early modern Japan and Ezochi.At the same time, the 1970’s also saw advances in research on Japanese “national seclusion” that took into its purview East Asia and it was in such a milieu that I undertook the study of Ezochi in the 1980’s with a view to understanding its history in connection with development in East Asia. In 1616 Jurchen kingdom of the Later Chin (later to be come to Ch’ing) was founded in Tatary corresponding to present-day northeastern China and the Jurchen and Tatary cannot be ignored when seeking to understand the foreign relation on early modern Japan.