Kai Chōshizuka Kofun: A Keyhole-Shaped Burial Mound in Japan
Site at a Glance
- Rating
- 4.3
- Popularity
- Low
- Country
- Japan
- Primary era
- Classical
- External website
- Open
- Eras represented
- Classical
- Civilizations
- Yamato
- Site type
- Burial
- Remains
- Burial Mound
On this page11 sections
History
Kai Chōshizuka Kofun is a late fourth-century keyhole-shaped burial mound in Kōfu, Japan, built within the Kofun-period burial culture. It is the largest kofun in Yamanashi Prefecture and ranks among the larger early Kofun-period tumuli of eastern Japan. The mound occupies the northern edge of the Sone Hills, beside the left bank of the Fuefuki River, at about 260 metres above sea level.
From Yayoi communities to the Kofun period
The surrounding area had developed productive capacity during the later Yayoi period, when the Uenohira site contained numerous square-moated burials. Burial customs associated with the Kofun period later entered the Kōfu Basin from the Tōkai region, passing through the western foothills of Mount Fuji and along what became the Nakamichi route. Tōkai-style pottery and S-shaped-rim jars reflect these connections.
Kai Chōshizuka formed part of the Higashiyama Kofun cluster, a concentration of large burial mounds that also included Ōmaruyama, Marukoyama, and Kankanzuka. Ōmaruyama preceded it and was the first keyhole-shaped mound in the Higashiyama area, where square mounds had previously been more usual. A keyhole-shaped kofun combines a circular rear section with a rectangular front section.
Yamato connections and regional authority
Keyhole-shaped kofun are generally associated with the influence of the Yamato polity, an early political power centred in the Kinai region around modern Nara and Osaka. During the late fourth century, Yamato influence extended into eastern Japan, and large keyhole-shaped mounds appeared across the Tōkai and Chūbu regions. These mounds are interpreted as expressions of the rank and political organization of regional chiefs.
Kai Chōshizuka is considered to have especially strong connections with the Kinai region. Its three-tiered rear mound, stone chamber, burial orientation, use of vermilion, stone facing, haniwa, and grave goods have been interpreted as sharing funerary forms and ritual practices associated with the Kinai and with Chinese traditions concerning immortals. A triangular-rimmed divine-beast mirror also encouraged the theory that the central Nakamichi area had entered the Yamato polity. The burial may have belonged either to a newly rising power or to a local authority descended from the earlier Yayoi elite, although this remains a historical interpretation rather than a certain identification.
After Kai Chōshizuka was built, the size of mounds in the Higashiyama area declined. From the fifth century, the political centre of eastern Japan is thought to have shifted towards the Kantō region, while smaller and more traditionally shaped kofun appeared elsewhere in the Kōfu Basin.
Traditions, worship, and changing names
The Kojiki and Nihon Shoki, early Japanese chronicles preserving dynastic, mythological, and historical traditions, relate that Yamato Takeru, the son of Emperor Keikō, stopped at Sakiori Shrine while returning from an eastern campaign. He is said to have exchanged a verse dialogue with an elder who tended a fire. Masayoshi Isogai and Hidesaburō Hara connected this elder with the person buried at Kai Chōshizuka and interpreted the story in relation to Yamato submission during the fourth century. Another interpretation places the tradition’s historical background in the sixth century.
The mound was already known as Chōshizuka in the 1814 geographical record Kai Kokushi. In the modern period, the Ise-kō used it as a place of worship, giving it the additional name Ise-zuka. Stone shrine and stone lantern facilities associated with that use were later moved during preservation work.
Investigation and preservation
A 1925 archaeological report described Kai Chōshizuka as a large keyhole-shaped kofun with a stone chamber, surrounding ditch, and haniwa. On March 17, 1928, construction connected with the Ise-kō led to the discovery and opening of the chamber. Large quantities of vermilion and burial goods were found inside. Ueda Sanpei, an archaeologist commissioned by the Ministry of Education, later compared the mound with kofun in the Kantō and Kinai regions and emphasized its strong Kinai connections.
Meiji University’s archaeology laboratory, directed by Hatsushige Otsuka, surveyed the mound in 1966, followed by further excavation by the Yamanashi Prefectural Board of Education in 1985. Most objects recovered in 1928 are now held by the Tokyo National Museum. Preservation and improvement works began in 1983, and the surrounding area became part of Sone Hills Park. Public acquisition of land around the rear mound continued from 1998 until its completion in 2004, with related investigations in 2001 and 2004.
The 2001 to 2004 investigations identified a semicircular protruding feature and ritual wooden objects. These discoveries were considered unprecedented among early kofun in eastern Japan and renewed scholarly and public attention. The wooden objects were displayed in archaeological exhibitions in 2006 and 2007. Kai Chōshizuka Kofun and the adjacent Maruyamazuka Kofun were designated together as a National Historic Site in 1930 under the name “Chōshizuka Kofun with Maruyamazuka Kofun.”
Remains
Kai Chōshizuka is an east-oriented keyhole-shaped mound measuring approximately 169 metres in total length. Its circular rear section is about 92 metres across and 15 metres high, while the rectangular front section is approximately 69 metres wide and 8.5 metres high. The rear section rises in three tiers and retains a covering of fukiishi, stones laid over the earthwork to protect and finish the mound’s surface. A single surrounding moat measured about 15 to 20 metres across.
Mound and burial chamber
A vertical stone-lined burial chamber stands where the mound’s east-west axis meets the circular rear section. Its walls were built from split stones laid with their ends facing inward, and the chamber had an earthen floor. Traces of a split-bamboo-shaped wooden coffin were identified. The chamber measures approximately 6.5 metres internally from end to end, 0.9 metres wide, and 1.2 metres high.
A thick layer of vermilion lay near the centre of the chamber, where burial goods had been placed. The assemblage included five bronze mirrors, four crystal magatama beads, a jasper tubular bead, six wheel-shaped stone ornaments, four iron knives, three iron swords, fragments of iron arrowheads, a rectangular iron axe, a bracelet-shaped stone object, stone and shell bracelets, and pestle-shaped wooden objects.
Bronze mirrors and ornaments
The five mirrors comprise a triangular-rimmed divine-beast and chariot mirror, an inner-facing floral mirror, a daryu mirror, a locally made triangular-rimmed divine-beast mirror, and a half-circle-and-square-banded ring-knob divine-beast mirror. The triangular-rimmed divine-beast and chariot mirror shares a mold relationship with mirrors from Bizen Kurumazuka Kofun in Okayama, Sanbongi Kofun in Gunma, and the Fujisaki site in Fukuoka. A mold relationship indicates casting from the same original mold or from closely related molds.
The imported inner-facing floral mirror bears the auspicious inscriptions “Long benefit to sons and grandsons” and “Long life like metal and stone.” Its knob is damaged, possibly as a result of deliberate destruction. The daryu mirror was made in Japan and drew on designs associated with earlier pictorial-banded and ring-knob divine-beast mirrors. The Kai Chōshizuka example has birds and diamond-cloud designs around its outer zone and a simplified inner zone.
The jasper wheel-shaped ornaments imitate bracelets made from large shells. They are circular, formed with narrow rings, and retain traces of vermilion. Their placement inside the wooden coffin is considered possible. The stone bracelets imitate female bracelets made from cone shells, while a further bracelet was made from the southern marine shell known as the suijigai.
Haniwa and funerary vessels
Ritual haniwa, clay funerary objects placed on or around burial mounds, included jar-shaped, cylindrical, and morning-glory-shaped examples. The early cylindrical pieces belong to a tradition associated with special ritual stands and share characteristics with examples from Matsubayashi-yama Kofun in Iwata and Asakozuka Kofun in Ōta.
An S-shaped-rimmed jar mounted on a pedestal was also recovered. This Tōkai-style vessel represents a newer form without horizontal comb-brushing on its exterior. Its surface was blackened and showed traces of exposure to fire, linking it with ceremonies performed at the kofun.
Wooden ritual objects
A semicircular protrusion extended from the moat on the northern side of the rear mound. Buried wooden posts were found in this area, which is interpreted as a place used for ritual activity.
Another group of assembled wooden objects came from the moat beside the western edge of the rear mound. One disk-shaped object measures approximately 50 centimetres across and 4 centimetres thick, with a lens-shaped thickening at its centre. Three holes around its edge appear to have held bracken-shoot-shaped wooden elements secured with pegs. A central mortise was designed to receive a rod-shaped element.
Many of the wooden pieces had been exposed to fire. A spatula-shaped object included a fire-drilling board, a board used with a fire-making implement to produce fire through friction. This feature supports their interpretation as equipment for funerary rites. The disk-shaped, bracken-shoot-shaped, and rod-shaped pieces remain comparatively well preserved, while a parasol-shaped object decayed through exposure to wind and rain.
The implements are thought to have been used for a limited period, possibly several years, before being thrown into the moat. Analysis found that a cedar post had broken in its upper half. Its non-heartwood timber came from a tree felled in the early third century, creating a chronological interval between the age of the wood and construction of the mound.
Maruyamazuka Kofun
Maruyamazuka Kofun lies approximately 80 metres east of Kai Chōshizuka’s front section. It is a circular mound about 72 metres in diameter and 11 metres high, built in two tiers with haniwa and a surrounding moat.
Excavated in 1904, Maruyamazuka contained a vertical stone-lined chamber measuring 5.5 metres at the summit. Its finds included a pictorial-banded divine-beast mirror, an iron sword, an iron axe, iron arrowheads, a sickle, and other objects. A separate clay floor may have yielded a stone bracelet.
