 A pair of forts (Mie gusuku and Yarazamori gusuku) built atop embankments extending out across the entrance to the harbor defended the port, and a small island within the harbor held a warehouse, "Omono gusuku" (御物グスク), used for storing trade goods.Tomari (泊), on the mainland of Okinawa Island to the northeast of Ukishima, served as the chief port for trade within the Ryūkyū Islands.The administrators of Tomari were also responsible for collecting and managing the tribute paid to the kingdom by the Amami Islands, whose tribute ships made port here.