Clay Products from the Akezima Kofun Group: A Window into Ancient Japanese Ritual Life

Tucked away in the modern cityscape of Iwata in Shizuoka Prefecture, an extraordinary collection of over one thousand miniature clay objects tells the story of spiritual life in ancient Japan. The Clay Products from the Akezima Kofun Group (静岡県明ヶ島古墳群出土土製品) were designated as an Important Cultural Property of Japan in June 2013, and they represent one of the most remarkable assemblages of Kofun-period ritual artifacts ever discovered in the country. These palm-sized, hand-crafted figurines and models offer visitors an intimate glimpse into the beliefs, ceremonies, and daily life of people who lived in this region more than 1,500 years ago.

What Are the Akezima Kofun Group Clay Products?

The Akezima Kofun Group (明ヶ島古墳群, read "Myōgajima") is a cluster of burial mounds dating from the middle to late Kofun period (roughly the 5th to 7th centuries CE), located in the Mitsuke district of Iwata City. During excavations carried out between 1994 and 2001 as part of a land readjustment project, archaeologists unearthed over 4,000 clay model objects from beneath and around the mounds. Of these, 1,064 well-preserved pieces were selected and designated as an Important Cultural Property, along with additional fragments catalogued as supplementary items.

Most of these artifacts were discovered beneath Mound No. 5, a square tumulus (方墳) measuring approximately 18 meters on each side. They were found in a specially carved-out feature in the ground, remarkably still in nearly their original positions — a rare circumstance that provides invaluable information about how these objects were originally arranged during ritual ceremonies.

Why Were They Designated as an Important Cultural Property?

The Akezima clay products earned their Important Cultural Property designation for several compelling reasons. First, the sheer number of objects is extraordinary — the total exceeds 4,000 pieces, with 1,064 items preserved in excellent condition. Second, the variety of forms represented is unparalleled among comparable sites nationwide. The collection encompasses human figurines, four-legged animal shapes, weapon models (swords, bows, arrows, quivers), armor forms (shields, cuirasses), mirror replicas, jewelry models (bracelets, beads), agricultural tool forms (axes, hoes), weaving implement models, and musical instrument shapes (various types of zithers).

What makes these artifacts particularly significant is the level of detail and intentional differentiation within each category. Among the human figurines — the most numerous type — craftspeople clearly distinguished between warriors, men, and women. The musical instrument models include three distinct varieties of koto-like stringed instruments: stick zithers, board zithers, and trough zithers. Many weapon and tool models faithfully reproduce structural details such as handle grips on shield forms, triangular plate foundations on armor, and pommel-end details on sword hilts.

Some objects even function as matched sets: quiver models paired with arrow models, and reel-stand (kasekake) models paired with spinning-wing (maiha) models. These combinations demonstrate a sophisticated ritual system in which specific groupings of miniature objects were laid out on the ground as offerings during ceremonies dedicated to spiritual beings. As a collection, they provide unmatched insight into the types, combinations, and practices of Kofun-period ritual activity.

Understanding Kofun-Period Ritual Clay Products

Unlike the more widely known haniwa — large hollow clay figures placed on and around burial mounds — the Akezima clay products belong to a different tradition of ritual objects known as clay imitation products (土製模造品, dosei mozōhin). These are small, solid objects molded by hand from clay and then fired. Typically small enough to fit in the palm of a hand, they were created as miniature symbolic representations of real objects and placed on the ground during ceremonies to invoke divine protection or offer prayers.

This tradition of creating miniature clay replicas for ritual use was widespread during the Kofun period, but the Akezima collection stands out for its exceptional quantity, diversity, and state of preservation. The practice reflects a belief system in which everyday objects — from farming tools to weapons to musical instruments — held spiritual significance and could serve as conduits between the human and divine worlds when offered in miniature form.

Importantly, the Akezima site also shows evidence of ritual continuity over time. While the main deposit dates to the first half of the middle Kofun period (around the 5th century), additional clay products were found in the surrounding ditches of Mound No. 5 and Mound No. 2, the latter dating to the late Kofun period. This suggests that the sacred site was used for ceremonial purposes across several generations.

Highlights and Must-See Items

Visitors to the Iwata City Archaeological Center will find a selection of these fascinating artifacts on display. Among the highlights to look out for are the human figurines, which despite their small size convey distinct personalities through their posture and clothing details. The warrior figures are particularly expressive, capturing the essence of armed guardians in miniature form.

The weapon and armor models are also remarkable for their technical accuracy. The sword models (tachi-gata) carefully reproduce pommel ends and tang details, while the shield models feature handle representations that mirror actual shield construction. The cuirass models show triangular lamellar plate patterns that correspond to real armor of the period.

The musical instrument models provide rare evidence of musical culture during the Kofun period. The three different types of koto represented — stick, board, and trough varieties — suggest a rich musical tradition that accompanied ritual activities. These are among the most unusual and informative items in the entire collection.

Animal figurines, including dogs and horses, add further charm and offer insight into the role of animals in ancient Japanese spiritual life. Each piece, while modest in size, is a testament to the skill and intention of its creator.

Where to See the Collection

The clay products are housed and displayed at the Iwata City Archaeological Center (磐田市埋蔵文化財センター), which is located at the same address as the cultural property's registered location: 3678-1 Mitsuke, Iwata City, Shizuoka Prefecture. The center serves as both a storage and research facility for archaeological materials excavated from sites throughout Iwata, and its first-floor exhibition space presents artifacts from the Paleolithic era through the medieval period, organized chronologically.

Admission to the center is free. Guided explanations of the exhibits can be arranged upon request, making it a particularly rewarding visit for those interested in learning more about the archaeological context of the clay products. The center is staffed by specialists from the city's Cultural Properties Division who can answer questions about the collection and other cultural heritage in the area.

Exploring the Surroundings

The Mitsuke district of Iwata is rich in historical interest, making it easy to combine a visit to the Archaeological Center with other cultural attractions in the area. The Tōtōmi Provincial Temple Ruins (遠江国分寺跡), designated as a Special National Historic Site, is located nearby and preserves the foundation layout of an 8th-century Buddhist temple built under Emperor Shōmu's decree. The site has been beautifully maintained as a historical park where visitors can stroll among the original foundation stones.

The former Mitsuke School (旧見付学校), one of the oldest surviving wooden school buildings in Japan, offers a look at Meiji-era education and architecture. Nearby, the Yahashira Shrine (矢奈比賣神社), known locally as Mitsuke Tenjin, is famous for its dramatic Hadaka Matsuri (Naked Festival), designated as a National Important Intangible Folk Cultural Property.

For those with broader interests, the Yamaha Communication Plaza in Iwata showcases the history and products of the Yamaha Motor Corporation, whose headquarters are in the city. The Iwata City Fragrance Museum (磐田市香りの博物館) offers an unusual hands-on experience where visitors can create their own custom perfume blends.

Nature lovers may wish to visit the Shishigahana Park (獅子ヶ鼻公園), known for its scenic hiking trails and cherry blossoms in spring, or the Kumano-no-Nagafuji wisteria trellis, a designated Natural Monument with a tree estimated to be 850 years old, which blooms spectacularly in mid to late April.