Koshidaka Site: Where Korean Neolithic Potters Settled on a Tsushima Shore
On a cliff-backed beach in the northwest of Tsushima, archaeologists uncovered a hearth built from flat slabs of stone, set in a square roughly 1.1 meters on each side. No contemporary site anywhere in the Japanese archipelago has produced anything quite like it. Its closest counterparts lie across the water, at the Dongsam-dong and Beombang shell middens near present-day Busan in South Korea.
That hearth, together with the thousands of pottery fragments found around it, is why the Koshidaka Site matters. It records, in clay and stone, one of the earliest documented moments of contact between the Korean Peninsula and the islands that would become Japan.
The site lies in Koshidaka, in the Kamiagata district of Tsushima City, Nagasaki Prefecture. It dates to the close of the Initial Jōmon period and the Early Jōmon that followed, roughly 7,100 to 6,400 years ago. On March 10, 2025, it was designated a National Historic Site, having previously held municipal and then prefectural protection.
Two Camps Above the Sea
The site is made up of two areas, named A and B, sitting about 50 meters apart on either side of a ridge that drops toward the shore. Area A occupies the coastal strip, close enough to the waterline that the sea has been steadily eroding it. Area B sits a short distance inland.
What unites the two is the pottery. The great majority of fragments recovered from both areas belong to a style called raised-band ware, or ryūkimon doki in Japanese. Potters made it by laying thin ribbons of clay onto the surface of a vessel and then pressing them with a fingertip or a nail to form raised decorative bands. This technique was a signature of the Korean Peninsula's early Neolithic. In the south of the peninsula it was being produced in quantity between roughly 5400 and 4400 BCE.
At nearly every other site in Japan, this kind of pottery simply does not appear. Koshidaka is the rare place where it dominates the assemblage.
Made Here, Not Carried Over
A simple story would have these vessels arriving as cargo, carried across the strait from Korea. The clay tells a more interesting version. Analysis of the fabric of the raised-band pottery found that some of it was made from clay sourced on Tsushima itself. The pots, in other words, were being formed on the island, not imported ready-made.
The stone tools point in a second direction. Among the finds were implements of obsidian and sanukite originating in northwestern Kyushu, the large island to the south. The people at Koshidaka, then, drew on a ceramic tradition rooted in southern Korea while also reaching toward communities in Kyushu for raw materials.
The most reasonable reading is that this was a settlement of people shaped by the Korean Peninsula's pottery culture, living on Tsushima and in contact with the Jōmon world to the south. Fishing appears to have been central to how they lived, which suits a community placed right at the water's edge.
Why the Designation Came When It Did
Koshidaka had been known to local researchers for decades, but a fresh round of excavation changed its standing. From 2015, Tsushima City's board of education worked alongside Kumamoto University to dig the two areas systematically. By the time of a public site briefing in 2018, around 470 pottery fragments had been recovered, the overwhelming share of them raised-band ware made with Tsushima clay.
The square stone hearth in Area A carried particular weight. Because its design matches hearths at the Dongsam-dong site and the Beombang shell midden in Busan, and because nothing comparable is known from the Japanese islands of the same age, it offered direct architectural evidence of people arriving from the peninsula.
Taken together, the pottery, the clay analysis, the imported stone, and the hearth make Koshidaka the oldest site yet identified on Tsushima. It is treated as a kind of origin point for the island's long role as a stepping stone between Korea and Kyushu, which is the reasoning behind its promotion to National Historic Site.
What There Is to See, and What to Expect
It helps to set expectations before making the trip. Koshidaka is an archaeological site, not a reconstructed village. There is no rebuilt longhouse, no museum on the spot. What rewards a visit is the setting itself: a working sense of why people chose this exact shore, with the strait opening toward the peninsula and the land rising behind into Tsushima's steep, forested interior.
The location that made the site valuable also makes it fragile. Sitting at the foot of a coastal slope, Area A takes the full force of waves, and typhoons and heavy rain have caused visible damage over the years. Browsing by the island's deer has added to the strain. The city has carried out conservation work to slow this erosion, and the results are reported to have helped.
Travelers who want to see the finds themselves should ask locally about current displays, as excavated material is held and studied through Tsushima City. The Agency for Cultural Affairs has also produced a short video on the island's archaeology, featuring Koshidaka, which is a useful primer before a visit.
The Wider North of Tsushima
Koshidaka sits in a part of the island where the closeness of Korea is hard to ignore. A short distance north, the Korea Observatory at Waniura looks out across water that narrows to about 49.5 kilometers from the peninsula. On a clear day the streets of Busan are visible, and after dark its lights show on the horizon. The building borrows from Korean architectural styles, a deliberate nod to the relationship that the Koshidaka people began thousands of years earlier.
Nearby, the Tsushima Wildlife Conservation Center introduces the Tsushima leopard cat, an endangered subspecies found only on the island, while the cape at Saozaki marks one of the most northwesterly points in Japan. Together these stops turn a visit into a fuller portrait of a border island.
Reaching Tsushima takes a flight into Tsushima Airport from Fukuoka or Nagasaki, or a ferry from Hakata Port in Fukuoka, which calls at Hitakatsu in the north and Izuhara in the south. The Kamiagata district, where Koshidaka lies, is in the island's north and is most easily reached with a rental car.
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Q&A
- What makes the Koshidaka Site important?
- Most of the pottery found here is Korean-style raised-band ware, and a square stone hearth matches examples near Busan rather than anything in Japan. The site gives rare, concrete evidence of contact between the Korean Peninsula and the Japanese islands roughly 7,000 years ago.
- Does that mean the pottery was brought from Korea?
- Not all of it. Clay analysis shows that some of the raised-band pottery was made from clay found on Tsushima, so the vessels were produced on the island even though the style came from the peninsula.
- When was it designated a National Historic Site?
- On March 10, 2025. It had earlier been protected as a municipal and then a prefectural historic site before the national designation.
- Is there anything to see if I visit?
- The site is an excavation area on the coast rather than a reconstructed attraction. The reward is the shoreline setting and its sense of place. For the artifacts themselves, ask locally about current displays through Tsushima City.
- How do I get to northern Tsushima?
- Fly into Tsushima Airport from Fukuoka or Nagasaki, or take a ferry from Hakata Port to Hitakatsu in the north. A rental car is the practical way to reach the Kamiagata district where the site lies.
Basic Information
| Name | Koshidaka Site (越高遺跡, Koshidaka Iseki) |
|---|---|
| Location | Koshidaka, Kamiagata, Tsushima City, Nagasaki Prefecture |
| Designation | National Historic Site (designated March 10, 2025) |
| Period | End of Initial Jōmon to Early Jōmon, about 7,100 to 6,400 years ago |
| Designated area | About 4,504 m² |
| Composition | Two areas (A and B), about 50 meters apart across a ridge |
| Key features | Korean-style raised-band pottery; a square stone hearth roughly 1.1 m per side |
| Access | Northern Tsushima, reached via Tsushima Airport or ferry to Hitakatsu, then by car |
References
- Database of National Cultural Properties, Agency for Cultural Affairs - Koshidaka Site
- https://kunishitei.bunka.go.jp/bsys/maindetails/401/00004221
- Cultural Properties of Nagasaki Prefecture - Koshidaka Site
- https://www.pref.nagasaki.jp/bunkadb/index.php/view/790
- Cultural Properties, Tsushima City
- https://www.city.tsushima.nagasaki.jp/gyousei/soshiki/kyouiku/bunkazaika/bunkazai/bunkazai/1051.html
- Korea Observatory - Nagasaki Tourism
- https://www.nagasaki-tabinet.com/guide/893
Last verified: 2026.05.28