Items Excavated from the Kojindani Site in Shimane Prefecture

358 Bronze Swords on a Hillside in Izumo

The Items Excavated from the Kojindani Site in Shimane Prefecture (島根県荒神谷遺跡出土品) are Yayoi-period bronzes recovered in 1984 at Kanba, Hikawa-cho, Izumo City, designated an Important Cultural Property on 6 June 1985 and a National Treasure on 30 June 1998. The listing covers 358 bronze swords, 16 spearheads and 6 bells as a single group. They belong to the national government and are held by the Shimane Museum of Ancient Izumo.

The find came out of a survey ahead of farm-road construction. A trench cut into a southeast-facing slope exposed row upon row of bronze swords, blades set upright, packed into the earth. When the soil was cleared the count reached 358. A few metres to the west lay a second pit holding 16 spearheads and 6 bells. Full excavation followed in 1985.

This single find more than doubled the number of Yayoi bronze swords excavated across the whole of Japan up to that point. Bronze swords, spearheads and bells of this kind were not battlefield gear or instruments in any everyday sense. By the time they were buried they had become ritual objects, made to be offered, raised or laid in the ground.

Why the Find Rewrote the Map

Before Kojindani, the bronze culture of the Yayoi period was generally read as two spheres: a bell-using region centred on Nara and Osaka, and a weapon-shaped-bronze region centred on northern Kyushu. Izumo, on the Sea of Japan between them, tended to be placed at the margin.

Then a single slope produced all three at once: swords of a form concentrated in Izumo, bells belonging to the Kinki tradition, and spearheads belonging to the northern Kyushu tradition. That these came together in one place through a formal excavation rather than a chance cut is what gives the assemblage its weight. Izumo emerged not as a periphery but as a place where different ritual traditions met.

The find forced a review of how bronzes moved through western Japan and what they meant. In 1996 the Kamo Iwakura site a few kilometres away produced 39 bronze bells, also now a National Treasure. The two sites together support placing Izumo near the centre of early Japanese history rather than at its edge.

What to Look For Up Close

The swords repay slow looking. All 358 belong to a single narrow type and run about 51 centimetres. They were laid in four rows counting from the west, of 34, 111, 120 and 93, each blade standing on edge.

Close study has turned up two things worth noting. Some were never given their final edge-grinding after casting, and many share moulds with one another across numerous combinations. Both point to concentrated production over a short span between the end of the Middle Yayoi and the start of the Late Yayoi.

The 16 spearheads divide into 2 of a narrow form and 14 of a broader one. Four carry togiwake on their surfaces: after the normal polish, the smith worked the metal again at a different angle, so that scattered light raises a herringbone pattern. The same effect appears on spearheads from Kemidani and Yoshinogari in Saga Prefecture, tying the Izumo group into the wider lineage of weapon-shaped bronzes.

The 6 bells each run about 22 centimetres and were laid in 2 rows of 3, handles facing one another and flanges upright. One belongs to the earliest stage and carries horizontal banding; the remaining 5 are of a slightly later flanged-handle type, their bodies divided into the four-panel crossed-band scheme.

Set the weapons and the bells side by side and the question this group carries takes shape in front of you. Why were ritual traditions from opposite ends of the archipelago laid together, this carefully, into one hillside?

Visiting the Site

One thing to settle first. The Shimane Museum of Ancient Izumo, which normally displays the bronzes themselves, is closed for seismic work and is due to reopen around October 2026. While it is shut, the place to go is the site itself.

The Kojindani Museum stands at Nishidani in Kanba, immediately beside the excavation. It is arranged so that visitors can stand where the bronzes came out of the ground, and its displays set out the circumstances of the discovery alongside replicas of the swords, spearheads and bells. The originals appear only during limited special showings, so anyone hoping to see them should check the schedule in advance. A short walk away, the excavation point itself is reconstructed with replicas in position, and the whole slope can be taken in from slightly above.

The surrounding Kojindani Historic Site Park opened in 1995 and holds enough to fill half a day. In mid-June some 50,000 ancient lotuses known as Oga lotus bloom in the paddy in front of the museum, reason enough for a visit on their own.

The museum opens 9:00 a.m. to 5:00 p.m., last admission 4:30 p.m., closed Tuesdays and over the New Year period. Driving is easiest: about 5 minutes from the Hikawa interchange of the San'in Expressway and about 10 from Izumo Airport. From Shobara Station on the JR San'in Main Line it is about 40 minutes on foot, or a short taxi ride.