The Genii Locorum of Saihoji
（First Part）
Yanase Hiroichi

The ancient Romans believed that all locations were inhabited by genii locorum —the protective spirits of places. The multilayered nature of time is a key concept for understanding the history of Saihoji. As we look back over the centuries, we find that through the layered tapestry of their activities, the human guardians of Saihoji through the ages can aptly be described as its genii locorum.

Once the site of a villa belonging to the famous Prince Shotoku (574–622), Saihoji will be celebrating its 1,300th anniversary in 2031. In February 2025, Professor Yanase of the Institute for Liberal Arts at the Institute of Science Tokyo visited Saihoji to deliver a lecture under the theme of the multilayered nature of time, offering his perspective from the vantage point of the river basin as he explored the background to the development of this area.

Yanase Hiroichi
Professor, Institute of Science Tokyo (Media Studies). Born in Hamamatsu, Shizuoka Prefecture in 1964, Professor Yanase is known for offering sharp insights regarding social, environmental, and cultural changes. Alongside his teaching work, he has published numerous books, including the bestseller Kokudō Jūroku Gōsen: Nihon wo Tsukutta Michi (National Route 16: The Road That Built Japan) (Shinchōsha) and Kawasemi Toshi Tokyo (Maboroshi no Tori wa Naze Kokyujutakugai de Kurasunoka) (Kingfisher City Tokyo: Why This Fabled Fowl Chooses to Live Near Luxury Housing) (Heibonsha).

Lord of the River Basin

The thing that struck me when I studied the terrain around Saihoji was that Saihoji is like the lord of the river basin. The Saihoji River runs right next to the temple, flowing through the mountains of Kitamatsunoo and down toward the plains, eventually converging with the Katsura River.

This is an overview of the Saihoji River basin. When viewed from above, you can see that the river spreads out into a alluvial fan at the point where it emerges from the mountains into the plains. This landform was created by sediment carried and deposited by the river. Saihoji stands at the starting point of the fan-shaped formation, where the mountains meet the plains.

Allow me to provide some of the historical background to the Saihoji River basin. About 1,800 years ago, a group of people known to us as the Hata clan came from the ancient Korean kingdom of Baekje and settled in Uzumasa, northeast of where Saihoji stands today. Such settlers from the Asian mainland were referred to as toraijin, meaning “the people who crossed over,” and were highly influential in Japan's history, introducing knowledge and technology to the archipelago. They began arriving in Kyoto from quite early on in Japan's history, with Uzumasa as one of their earliest destinations. One of the places the toraijin settled was the Saihoji River basin.

Land Carefully Chosen for Its Merits

I believe that the abundance of water resources in this area played a major role in influencing the Hata clan's decision to establish their base in the Saihoji River basin. There are two springs at Saihoji, said to have been discovered by Prince Shotoku, that continue to flow copiously today.

Spring water has always been one of the most important resources for human life. People can survive for about two weeks without food, but only three days without water. That is why people throughout human history have built settlements along rivers and springs, nurturing civilization itself with the fresh waters that flowed from them.

Farther up the mountains, beyond Saihoji and along the Saihoji River basin, sits a cluster of ancient kofun burial mounds, offering evidence that the Hata clan settled here amid springs and small river basins. Kofun were generally built together with rice paddies, indicating that the people in this area must have had the technical skills and financial resources necessary to construct these huge tombs, as well as abundant food supplies.

Furthermore, living along the ridge of a mountain helps to avoid flood risk. The location that the Hata clan chose to establish their base was convenient for daily life, had a secure water supply, was suitable for rice cultivation, and was safe from flooding. In other words, it was prime real estate for the time.

The History of Saihoji, Nurtured by the Flowing Waters

The large Katsura River flows in close proximity to Saihoji. As Japan transitioned from the Yayoi Period (c. 300 BC – 300 AD) to the Kofun Period (c. 250–538 AD), boats and other water transportation technologies improved, and major rivers throughout the land came to be used for logistics and transportation. The Saihoji River basin, which connects to the Katsura River, must have been a convenient place to live for the easy access it offered to transportation and distribution routes.

The Kinai region, which encompasses present-day Nara, Kyoto, and Osaka, became the undisputed center of Japan during the Kofun Period. Underpinning this development were the advancements in shipbuilding technology that supported logistics and transportation by enabling the exploitation of the water systems linking the Seto Inland Sea to Lake Biwa. The Yodo River system that connects Lake Biwa to Kyoto and Osaka was a part of this logistical network. Fish from Wakasa Bay was transported over land from Lake Biwa, while goods from the Seto Inland Sea were transported by ship to Osaka. Although Kyoto was inland, the rivers provided access to the sea. The Katsura River is part of the Yodo River system, so it was only natural that the technically proficient toraijin would establish a base close to Saihoji.

Techniques for controlling river basins developed gradually from the Kofun Period. Indeed, the burial mounds themselves could not have been built without the civil engineering techniques used to control the river. People settled in the vicinity of small rivers that were easier to control. After that, the basin of the adjacent Uji River system became the nation's capital. This all shows how the site where Saihoji stands today had been recognized as significant by influential figures even before Kyoto became the capital.

Preserved Alongside Temples and Shrines: Kyoto's Diverse World of Water and Forests

Earlier as I walked through Saihoji, I saw a kingfisher. As it happens, kingfishers and humans share many preferences in terms of where to live. The kingfisher population is currently growing in Tokyo, with especially high numbers in areas with luxury housing. This is because Tokyo's upscale residential areas almost always include parks with spring water or ponds and other bodies of water fed by springs. Shakuji Park in Nerima Ward, once the site of a mighty castle belonging to the powerful Toyoshima samurai clan, features such a spring, as does Shinjuku Gyoen National Garden, where many feudal lords (daimyo) once kept their residences in the capital.

Spring water flows at many points around the Musashino Plateau, which was formed by the Tama River. There are as many as 700 such springs, just in the part of the Musashino Plateau that lies within the borders of the city of Tokyo. People have gathered around these springs and formed settlements since the Paleolithic era (approximately 38,000 to 16,000 years ago), and human activity has continued there ever since. As the warrior class gained prominence toward the end of the Heian Period (794–1185), leading clans built castles, while in the Edo Period (1603–1867), the three branches of the Tokugawa clan and the daimyo families who had historically supported the Tokugawa built their mansions here. Following the Meiji Restoration that began in 1868, the sites of the former daimyo residences came under the control and protection of powerful zaibatsu business conglomerates and the imperial family. Most of these properties became parks after the Second World War, and the majority of their springs are protected to this day.

As for how the natural environment with its spring water has been preserved in Kyoto, temples and shrines have played the same role as the grand daimyo residences in Tokyo. Temples and shrines were built in the most richly blessed locations, allowing the precious natural spring water to be preserved and maintained for over 1,000 years. I believe that this has led to the preservation of Kyoto's diverse waters and forests.

In short, Saihoji is blessed with water and is located in an environment that people have long considered ideal for living. I believe that it is precisely these local conditions that define Saihoji's position, underlining the need for people to continue revering it as the Moss Temple to this day.

In the second part, we will explore the changes in the natural environment and the important perspectives needed to carry Saihoji into the future. It is scheduled to be released in early September.

Edited by: MIYAUCHI Toshiki
Written by: FUKUDA Anna
Photographed by: Saihoji
*These photos were with permission.