Therefore, the number of Japanese daimyo (feudal lord) and merchants trading with Korea rapidly increased, but because some of them turned into wako (Japanese pirates) once they found unfavorable terms of trade, the Korean government eventually restricted the port of entry for koriwasen (ship for trading with Korea) only to Busanpo, Tongne Prefecture (present Busan Metropolitan City), the location where Local naval officer of Gyeongsang left-sided Prefecture was, and, Naijiho, Jinhae Prefecture (present, Jinhae City, Gyeongsang-namdo Prefecture), the location where Local naval officer of Gyeongsang right-sided Prefecture was, around 1407.
このため、日本の大名、商人らが朝鮮に通交する者が急増したが、彼らの中には交易に不都合があると倭寇に変貌するような者もいたので、朝鮮政府は1407年頃国防上の見地から興利倭船の入港地を慶尚左道都万戸所在地の東莱県富山浦（現在の釜山広域市）と慶尚右道都万戸所在地の金海府乃而浦（現在の慶尚南道鎮海市）に限定した。