The Continuous Quest for the East: From Hyuga to the Katori Sea

 

I. The Departure from Hyuga

Ugaya, whose ancestors originated from a region later mythologized as Takamagahara, ruled the Hyuga region on the eastern coast of Kyushu. Abandoned by his mother in infancy and raised by his aunt, he later married her and had four sons: Itsuse, Inahi, Mikenu, and Sano.

Tragedy eventually fractured the family. Inahi perished at sea while searching for his mother, and Mikenu sailed eastward, vanishing toward the "land of the dead." The remaining brothers, Itsuse and the youngest, Sano, embarked on a northward expedition. While the exact cause of this migration remains unknowable, it marked the beginning of a centuries-long expansion.

II. The Conquest of Yamato

Itsuse moved eastward along the Seto Inland Sea, spending years in Aki and Kibi to consolidate power. However, at the eastern terminus of the Inland Sea, he was wounded in battle against a local leader named Nagasune and died at Port O in the Kii region.

Sano took up his brother’s fallen mantle. Guided by a local tribe identified by the symbol of a three-legged crow, he navigated the treacherous Totsu and Yoshino Rivers to reach the Yamato Basin. Through a combination of subversion, underhanded assassinations, and "pork-barrel" political maneuvering, Sano dismantled local resistance and established his seat of power in Iware. Until the end of World War II, these events were widely believed in Japan to have taken place over two millennia ago.

III. The Katori Sea: Gateway to the East

Sano’s descendants continued this eastward quest, establishing crucial advanced bases as they pushed further. Beyond Kumano, they reached Ise, building the Ise Shrine at the southern edge of the Ise Plain. In the Owari region, they secured the river mouth with the Atsuta Shrine.

They were not voyagers of the open ocean, but masters of the coastline and inland waterways. Their expansion was a methodical leap from one bay to the next, securing the 'stepping stones' of the archipelago.

The expansion eventually reached the Kanto Plain, which was then dominated by a massive geographical feature: the Katori Sea. Known then as Uchi-umi (Inland Sea) or Nagare-umi (Flowing Sea), this water body was the strategic heart of the East. The Katori Shrine was established on its southern coast, functioning not merely as a place of worship, but as the administrative and military gateway to the Kanto Plain.

The shrine commanded 77 ports across Shimousa and Hitachi Provinces, governing the "sea people"—fishermen and sailors—who served as the empire’s navigators. By establishing maritime checkpoints to collect tolls and taxes—much like the "pirates" of the Seto Inland Sea—the central power solidified a system of resource extraction that fueled further expansion.

IV. The Launchpad for the North

The raw power of the Katori Sea was immortalized in the Man'yoshu by the poet-soldier Hasetsukabe Atahiohohiro: “A wave suddenly washed over the bow; / The spray unexpectedly fell over me.” Like many others, he was swept into the state's military machine, sent to the distant west as a sakimori, while the logistical might of the Katori network was turned toward the north.

On the northern shore of the Katori Sea, across the water from Katori, the Kashima Shrine was established. This was the final logistics hub, a forward command post designed for the relentless invasion of Northern Japan. Backed by this sophisticated deprivation system, on January 11, 802, the government ordered 4,000 young farmer-soldiers to migrate north. Driven by the allure of colonial profit and the momentum of a quest that began centuries earlier in Hyuga, the Yamato forces finally crossed the threshold into the deep Tohoku frontier.