Get to know the castle
Castle at a glance
- Site & layout
- Group of Ainu chashi sites
- Origins
- Approximately sixteenth–eighteenth centuries; exact dates unknown
- Builders & patrons
- Ainu communities
- Other names
- —
- What remains today
- Ditches, earthworks and level areas on coastal cliffs
THE STORY
The story behind the walls
The exact construction dates are unknown; the local chashi are generally dated to around the sixteenth to eighteenth centuries. Twenty-four of the thirty-two sites recorded in Nemuro form the designated historic group. Their earthworks remain visible along the coast. Surveys and research continue to clarify their shapes and varied roles.
LAYOUT & ARCHITECTURE
Read the landscape and the buildings.
Many sites use a sea cliff as one boundary and ditches to enclose the landward side. Semicircular or rectangular trenches and mounds, rather than masonry keep platforms, reveal their layout. Some combine several enclosed areas.
A CLOSER LOOK
Details worth a closer look.
Onnemoto Chashi
An earthwork on a headland west of Onnemoto Bay contains two level areas divided by ditches. Look at how the enclosure adapts the natural cape.
Notsukamafu ditches
Notsukamafu Sites 1 and 2 have semicircular ditches above the sea. Comparing them reveals differences in the size and depth of their enclosures.
More than a fort
Chashi are understood to have served ritual, observation, discussion and defensive purposes. Their meaning belongs within Ainu culture, rather than a single military model.
THROUGH THE YEARS
A short timeline
- c. 16th–18th centuries
Approximate period when the Nemuro chashi were built.
- 1983–1984
The sites received national historic designation in two stages.
- 2006
The Japan Castle Foundation selected the group among its 100 Great Castles.
BEFORE YOU GO
A note before you go.
Check current visitor routes with the tourism association. At Onnemoto, use the designated parking area and stay out of the fishing port, private land and workplaces. Sites are not cleared of snow in winter.
Information checked: 27 September 2026
Sources & official information
- Nemuro City: Chashi sites ↗
- Nemuro Tourism Association: Onnemoto Chashi ↗
- Cabinet Office: Nemuro Ainu policy project plan ↗
Some official sources are available in Japanese only.
