A major basis for the Satto explanation concerns the so-called "thirty-six families." These were families of learned men who came from China and settled in Okinawa. They took up residence in Kume Village, between Naha Port and Tomari Port, where they played a key role in the tribute trade. And this tribute-cum-trade system began during the reign of King Satto. Other supporting evidence for this theory includes the opening by King Satto of Gokoku Temple at Naminoue, his construction of the Banju Temple near Shuri and the fact that he caused likenesses of himself to be sculpted and enshrined there for the afterworld. Satto's son and successor, Bunei, built the Tenshikan in Naha during his reign as king of Chuzan to host the Chinese Sappo envoys. This, too, suggests that the king's seat had already been moved from Urasoe Castle to Shuri.

On the other hand, numerous sources establish that Sho Hashi spearheaded the first Sho Dynasty and unified the three kingdoms into one in the early 15th century from a base at Shuri Castle. This event is specifically estimated to have occurred in 1406. Thereafter, Ryukyu turned from military power to economic power and men with trading rights in the fine ports below the great castle came to the fore. According to the Sho Hashi explanation, the chief trading port was moved from Makiminato to Tomari in the time of King Eiso. It was then moved to Naha Port near Shuri after Sho Hashi shifted his base from Urasoe Castle to Shuri. There certainly can be no doubt that during the reign of King Sho Hashi, relations with China became ever more active and Naha Port, as the focal point of foreign trade, made a splendid contribution to the development of the economy and culture of Ryukyu. And likewise, it was Sho Hashi who planned and carried out the work that made Shuri Castle the splendid capital that it became, encircling the castle with stone works and putting up new buildings one after another.