In the San'in region, particularly around Izumo, a distinct political power existed from the late Yayoi to the Kofun period, separate from the Yamato polity. Its existence is supported not only by historical records but also by a wide range of archaeological evidence.

For example, the Mukibanda Yayoi Settlement Site—one of the largest in Japan—demonstrates the presence of a large population and a highly organized social structure in this region. In addition, the uniquely shaped “four-cornered protruding burial mounds,” distributed mainly across the San'in region, reflect a distinctive burial tradition not seen elsewhere in Japan.

Furthermore, the Kojindani and Kamo Iwakura sites are among the most significant bronze artifact discovery sites in Japan, suggesting that this region once functioned as a major center of ritual activity and political power.

The distribution of these archaeological sites across present-day Tottori and Shimane Prefectures indicates that this was not merely a collection of local settlements, but rather a regional polity with a strong degree of integration. In other words, San'in can be understood as one of the major powers of ancient Japan during the Yayoi period.

As the Izumo polity was incorporated into the Yamato state, significant changes occurred in the region’s society and culture. While maintaining aspects of its indigenous traditions, new systems influenced by the central government gradually took root.

One key example is the emergence of kofun (keyhole-shaped burial mounds). In the San'in region, sites such as the Mukaiyama Kofun Group and the Yamashiro Futagozuka Kofun indicate the presence of powerful local elites operating within the Yamato political sphere. In later periods, Buddhism also spread, leading to the construction of temples. These developments reflect the integration of San'in into the cultural and political framework of the central state.

With the establishment of the Ritsuryō state, administrative systems became more structured. Provincial capitals (kokufu) were established across San'in, and sites such as the Hōki Provincial Capital and Izumo Provincial Capital preserve traces of this system.

In addition, ancient road networks were developed, integrating the region into a broader national system. The Aoya Kamijichi Site and the Izumo San'indō Road Site reveal the structure of these routes, which connected San'in from east to west.

As shown in these two images, officials of the time would have traveled along these routes when moving between Heijō-kyō and the San'in region.

In this way, San'in transitioned from a region of independent local powers to one integrated into a centralized state. The remains of burial mounds, temples, provincial capitals, and roads serve as crucial evidence of this transformation.

With the arrival of Buddhism from the central government into a society originally based on early Shinto beliefs, the culture and religious landscape of the San'in region changed significantly. In addition to traditional reverence for nature and ancestors, new religions were accepted, forming a society where multiple beliefs coexisted.

As the Ritsuryō state developed, provincial governors sent from the capital worked to implement centralized systems. While doing so, they continued to visit local shrines that had been worshipped since the Yayoi period, and also participated in the construction of provincial temples such as kokubunji and kokubun-niji. In this way, a culture of Shinto-Buddhist coexistence became established in the region under state influence.

Furthermore, myths and legends passed down in the San'in region were incorporated into the "Kojiki" and "Nihon Shoki," becoming part of the national mythology alongside the formation of the state.

At the same time, documents such as the "Izumo no Kuni Fudoki" preserve local myths and oral traditions in their original form. These records show that even within national integration, the unique culture of the San'in region remained strongly preserved.

In this way, San'in developed a culture in which Shinto and Buddhism coexisted, and where local traditions continued to be passed down even as myths were organized by the state. The traces of this cultural diversity, maintained within national integration, can still be found in ancient texts and regional records.

Izumo Taisha is not merely a shrine, but a symbol that preserves the historical flow from an independent regional polity to the formation of a unified state. Because of San'in's strong presence in the Yayoi period, this site came to embody the intersection of faith, mythology, and state formation.

Some theories suggest that the unique architectural techniques seen at Izumo Taisha may date back to the Yayoi period. Originally, this site began as a local place of worship rooted in the region.

With the establishment of the Ritsuryō state, its role changed significantly. The shrine, once a local spiritual center, became incorporated into the national religious system and gained importance as a key site connected to the central government.

Izumo Taisha is also mentioned in national chronicles such as the "Kojiki" and "Nihon Shoki," appearing within the mythology that supports the legitimacy of the state. Through this position, it transcended its role as a regional shrine and became part of the nation's mythological framework.

In this way, Izumo Taisha symbolizes the integration of faith, mythology, and state in ancient San'in, preserving the historical layers formed through their intersection. Its existence, where myth and history intertwine, represents what can be called "another beginning of Japan."