The Tatetsuki Site, the sacred object of Tatetsuki Shrine, the “spiral-patterned stone,” and Koikui Shrine — mysterious ruins and a legendary shrine that have endured for approximately 1,800 years.

Tatetsuki Site is an archaeological site located on a hill amid a residential area in eastern Kurashiki City.

In fact, Tatetsuki Site is a little-known spot featured on popular television programs and visited by history enthusiasts from all over Japan. A shrine called “Tatetsuki Shrine” once stood here, where a mysterious stone engraved with beautiful patterns, the Sentaimon Stone, was enshrined as its sacred object.

Later, during the Taisho era, Tatetsuki Shrine was dismantled following its merger with other shrines, and for a time its sacred object was transferred to nearby Koikui Shrine. Koikui Shrine is also said to be connected to the Momotaro legend.

Here, we introduce the three sites—the Tatetsuki Site, the Sentaimon Stone, and Koikui Shrine—along with a mysterious story that dates back approximately 1,800 years.

The information presented was current when this article was published in October 2025. Please note that it may differ from current information.

One of the largest burial mounds of the Yayoi period: What are the Tatetsuki Site and the “Sentaimon Stone,” the sacred object of Tatetsuki Shrine?

Tatetsuki Site is a burial mound from the late Yayoi period (approximately 1,800–1,900 years ago), and is one of the largest of its time.

It is believed that a person equivalent to a king who ruled the Kibi region at the time was buried here. This valuable site marks the transition from the Yayoi period to the Kofun period, and was designated a National Historic Site in 1981.

The site has three main features.

Among the largest burial mounds of the Yayoi period, with a distinctive shape
Precious burial goods excavated from the burial mound
The mysterious “Sentaimon Stone”

Among the largest of the Yayoi period, with a distinctive shape

The mound is believed to have had a distinctive shape, with rectangular extensions to the northeast and southwest of a central “round hill” (circular mound). The central circular mound is approximately 50 meters in diameter, and the total length, including the extensions, is estimated at approximately 80 meters, making it one of the largest in all of Japan for the Yayoi period.

Model of the Tatetsuki Site (Image courtesy of Kurashiki City)

Five large stones stand atop the mound, some of which are over 3 meters tall.

The name Tatetsuki Site is also said to derive from a legend that Prince Kibitsuhiko built a “shield” to block an arrow shot by the demon Ura during their battle. Prince Kibitsuhiko is said to have been the model for Momotaro.

Precious burial goods excavated from the burial mound

According to excavations conducted by Okayama University beginning in 1976, a double-layered wooden coffin surrounded by wooden boards was found at the center of the burial mound. Its bottom was covered with an estimated total of more than 32 kilograms of mercury vermilion. Mercury, the raw material, was extremely valuable at the time.

Other grave goods reportedly included an iron sword and beads such as magatama (comma-shaped beads), kudatama (cylindrical ornaments), and small glass beads.

Many other items were also found, including special stands called “tokushu kidai,” used in rituals.

The mysterious “Sentaimon Stone”

In a repository close to the circular mound, a stone carved with what looks like a face rests quietly. This is the Sentaimon Stone, an Important Cultural Property of Japan. It is also called the “Kotaimon Stone” because of the shape of its pattern.

The Sentaimon Stone was once enshrined as the sacred object of Tatetsuki Shrine, which stood here.
During the Taisho era, the sacred object was also transferred to Koikui Shrine when the shrines were merged, but it was later returned to Tatetsuki because of reasons such as the spread of an epidemic.

For a long time, it remained a mystery when, by whom, and for what purpose the stone, engraved with beautiful belt-like patterns, was made. However, the discovery of another Sentaimon Stone that had been deliberately broken into pieces helped unravel some of the mystery.

Today, it is thought that the Sentaimon Stone may be evidence of a special ritual performed when the king who ruled this region died.

The round section in the center is carved to look like a face.

Face-like carving in the center front of the Sentaimon Stone

Patterns are also found on the back of the Sentaimon Stone

Koikui Shrine and the Momotaro legend

The unusual name “Koikui Shrine” comes from an episode in a legend passed down in this area.

Long ago, Prince Kibitsuhiko fought a fierce battle with the demon Ura.
When the cornered Ura transformed into a carp and fled into the river (Chisui River), Prince Kibitsuhiko immediately transformed into a cormorant, caught the carp, and ate it at this spot, according to legend. The villagers built Koikui Shrine here to enshrine this event.

Koikui Shrine has a long history, and its current shrine building was constructed in 1701, during the Genroku era of the Edo period.

Highlights of the Tatetsuki Site, the Stone with Spiral-Band Patterns, and Koikui Shrine

We spoke with a representative of Kurashiki City’s Japan Heritage Promotion Office about the Tatetsuki Site, the Stone with Spiral-Band Patterns, and Koikui Shrine.

Features of the Tatetsuki Site

What period does the Tatetsuki Site date from, and what are its features?

Kurashiki City

This site dates from around the end of the Yayoi period, when people began building large earthen tombs (mound tombs) for kings. At this stage, their shapes had not yet become standardized like the keyhole-shaped burial mounds of the Kofun period.

What has been learned through excavations?

Kurashiki City

About 30 special stands and special jars have been unearthed. We cannot say for certain exactly how they were used, but they are thought to have served as important ritual implements. In the Kofun period, the special stands became simpler and smaller in decoration and evolved into cylindrical haniwa clay figures.

In addition, about 32 kg of “mercury vermilion” was packed tightly across the bottom of the wooden coffin. In the thickest places, it was 5 cm deep.

The mercury used as a raw material came from both China and Japan, suggesting that there was exchange with China.

Shrine where the Stone with Spiral-Band Patterns was once enshrined

About Koikui Shrine

What are the highlights of Koikui Shrine?

Kurashiki City

In fact, Koikui Shrine is also a Yayoi-period mound tomb, although a small one.
Fragments of stones bearing spiral-band patterns were found here, too. It is thought to be a tomb from one generation after the Tatetsuki Site.

Important archaeological sites and a shrine steeped in legend in Kurashiki are places where you can feel the power

We explored the mysterious Tatetsuki Site and the Stone with Spiral-Band Patterns in Kurashiki, as well as Koikui Shrine, where the Momotaro legend lives on.

The Tatetsuki Site, the largest royal tomb of the Yayoi period, is striking for its large standing stones. The Stone with Spiral-Band Patterns is decorated with mysterious designs that spark the imagination of those who see it. The stone is usually kept in storage and is not open to the public, but you can view the sacred object through a small window beside the storage facility.

Koikui Shrine, whose origins lie in the legend of Prince Kibitsuhiko-no-Mikoto, said to be the model for Momotaro, and the demon Ura, is also a shrine with a tranquil atmosphere. The shrine has an impressive pair of guardian lion-dogs. It is said that one was once stolen and later returned, which is why the shrine is also known as a place where “lost things turn up.”

Take your time exploring Kurashiki’s important archaeological sites and shrines steeped in legend, and experience their charm and energy.