ChashiMountain castle (yamajiro)Japan's 100 Fine Castles No. 1
What makes this castle distinctive
Number one on Japan's list of 100 great castles has no keep and no stone walls: just ditches and earth mounds dug by the Ainu on headlands above the sea.
Why?
Chashi is an Ainu word meaning "fenced enclosure." Chashi are thought to have served as forts, but also as places for ceremonies, lookouts and negotiations. They have nothing in common with the castles that samurai lords (daimyo) built in mainland Japan, yet when the Japan Castle Foundation chose its 100 Fine Castles of Japan in 2006, it put the Nemuro Peninsula chashi at number one. Two of the 24 designated sites are open to visitors.[1][2][3][8]
Onnemoto Chashi, shaped like a New Year rice-cake offering
Where
A headland jutting out from the west shore of Onnemoto Bay, about 10 minutes by car from Cape Nosappu. A footpath leads to the site.
What to look at
The earth piled up on the headland, divided by ditches, with two flat areas made on top. From the Onnemoto fishing harbor side you can take in the whole shape.
Why it's interesting
Nemuro City says that from the harbor, the rounded mounds look like kagami-mochi, the stacked rice cakes offered at New Year. It is known as one of the best-preserved chashi. Nearby are pit dwellings from the Okhotsk culture, about 1,300 years old, showing that people have used this bay for a very long time.[1][9][11]
Can you see it?
Visible from outsideFree to visit outdoors. Private homes and kelp-processing areas surround it and are off limits; park only in the designated lot. The site is not cleared of snow in winter.
02
Notsukamafu Chashi No. 1 and No. 2, above the Sea of Okhotsk
Where
On a cliff-top headland jutting into Notsukamappu Bay (Makinouchi, Nemuro), about 20 minutes by car from central Nemuro.
What to look at
The half-moon ditches curving around the cliff top. At No. 1, two linked ditches about 5 m wide and 3 m deep spread over an area of 70 by 25 m. Look for the earth banked up on the inner side.
Why it's interesting
Many chashi in Nemuro have half-round or square ditches around a cliff top facing the sea, and this is a typical example. The same cape is where Russian traders arrived in 1778 asking to trade, and where 37 Ainu were executed after the Kunashir-Menashi conflict of 1789.[1][4][10]
Can you see it?
Visible from outsideFree to visit outdoors. Parking for only about two cars. Not cleared of snow in winter.
03
Models and finds at the Nemuro City Museum of History and Nature
Where
209 Hanasakiko, Nemuro, about 10 minutes by taxi from JR Nemuro Station.
What to look at
Finds from local archaeological sites, displays on the chashi, and a diorama.
Why it's interesting
On site you see only mounds and ditches, so getting a feel for their layout and uses at the museum first makes a big difference. The city has also published drone-surveyed relief maps and 3D models of the chashi. The museum itself is a brick building put up in 1942 as a naval communications post.[1][5][3][9]
Can you see it?
Visible from outsideFree admission. Closed Mondays, national holidays and over New Year. Has the Japan 100 Castles stamp.
At a glance for visitors
Nearest station
from JR Nemuro Station
Climb
Not confirmed
Time neededEditors' estimate
Allow 20–30 minutes on site at each chashi. Seeing both and the museum takes about half a day by car.
Admission
Free
Hours
9:30–16:30
Access
Partly open
Only two sites can be visited: Onnemoto Chashi and Notsukamafu Chashi No. 1 and No. 2. The other 22 are normally closed. Around Onnemoto there are private homes and kelp-processing yards; do not enter the fishing harbor or boat slipways. Roadside parking outside the designated lot is banned, and the city and tourism association warn that visits may be stopped if the rules are ignored. The sites are not cleared of snow in winter. The Japan 100 Castles stamp is at three places: the Museum of History and Nature, the Tourist Information Center next to Nemuro Station, and the Northern Territories museum at Cape Nosappu.
A chashi is an enclosed site built by the Ainu, the Indigenous people of Hokkaido. The word means "fenced enclosure" in the Ainu language, and chashi are thought to have been used not only as forts but also for ceremonies, as lookouts and as places to negotiate. About 500 chashi sites are known in Hokkaido. They differ in both builders and purpose from the castles that daimyo built as seats of government in mainland Japan.[1][3]
02
Historical record
On cliffs above the sea
Nemuro City has 32 chashi sites, and 24 of them are designated together as a National Historic Site, the Nemuro Peninsula Chashi Sites. Most sit on coastal cliffs 5 to 50 m above sea level, with half-round or square ditches dug around them, a type known as mengai-shiki (cliff-facing). Many are large, with several ditches combined, and they are packed more densely here than elsewhere. No record names who built them, and they are dated only roughly to the 16th to 18th centuries.[1][2]
03
Historical record
The Kunashir-Menashi conflict of 1789
In the Edo period, trade in this region was run by merchants who had bought the rights from the Matsumae domain, and they forced Ainu people to work at fishing grounds through violence and threats. In 1789 Ainu on Kunashir Island and in the Menashi area across the strait rose up and killed 71 Japanese. A record compiled in 1798 says that Tsukinoe, the chief leader of Kunashir, built a chashi there to prepare for battle, and that Nochikusa, chief of Shamokotan (today's Toyosato in Nemuro), built five chashi. But no direct battle followed. The 37 men who had taken part in the killings were brought to Nokkamappu and executed.[1][4]
04
Scholarly interpretation
Among the last chashi to be built
Nemuro City notes that its chashi draw attention for their possible links to the 1789 conflict and are considered to date from the last period of chashi building in Hokkaido. When and why each chashi was used differs from site to site; not all of them were forts for fighting.[2][1]
05
Historical record
Ditches that never filled in
No buildings or fences survive, but in Nemuro the ditches of chashi and the hollows of old pit dwellings have never completely filled in, so you can still see them as dips and rises in the ground. The city has used drone laser surveys to map them and has released 3D video of four chashi, two of which are normally closed to visitors.[1][3]
06
Historical record
Historic Site, Castle No. 1, Japan Heritage
The sites were designated a National Historic Site in 1983, with more land added in 1984. After being named No. 1 of the 100 Fine Castles of Japan in 2006 they drew visitors from Japan and abroad, and the city built footpaths at Onnemoto and Notsukamafu. In 2020 they became part of the Japan Heritage story "The Sacred Land of Salmon," about 10,000 years of people living with salmon along the Nemuro Strait. Every year since 1974, at the end of September, an icharpa memorial ceremony led mainly by Ainu people has been held at Nokkamappu for the Ainu and Japanese who died in the 1789 conflict.[2][6][4][7]
Russian traders arrive at Nokkamappu asking to trade[1][4]
Kunashir-Menashi conflict; 37 Ainu are executed at Nokkamappu[1][4]
The icharpa memorial ceremony begins at Nokkamappu[4]
Designated a National Historic Site (more land added in 1984)[7][2]
Named No. 1 of the 100 Fine Castles of Japan[2][8]
Becomes part of the Japan Heritage story "The Sacred Land of Salmon"[6]
Buildings and remains
The keep today
No keep was built
Chashi are enclosures of ditches and earth mounds built by the Ainu; they never had keeps or stone walls.
The site today
Of Nemuro's 32 chashi sites, 24 are a designated National Historic Site. Most lie in grassland or wild land on coastal cliffs. Only two, Onnemoto Chashi and Notsukamafu Chashi No. 1 and No. 2, have footpaths and are open to visitors.
Main buildings
Site onlyPart of a National Historic Site
Onnemoto Chashi site
Earth mounded on a headland, divided by ditches, with two flat areas on top. Footpath.[1]
Site onlyPart of a National Historic Site
Notsukamafu Chashi No. 1 and No. 2
No. 1 has two linked half-round ditches about 5 m wide and 3 m deep; No. 2 has a shallow ditch about 3 m wide and 0.5 m deep.[1][10]
Key facts
Type
Chashisites built by the Ainu people, used as forts, ritual places or meeting grounds; not the same as samurai castles
Setting
Mountain castle (yamajiro)built on a mountain; expect a climbEditorial article
Period
Medieval (c.1185–1570s), Early modern (1570s–1871)Editorial article
Keep (tenshu)
No keep was builtthe castle never had a keepEditorial article
National Historic Site (Nemuro Peninsula Chashi Sites) (1983); Component of the Japan Heritage story "The Sacred Land of Salmon" (2020)Editorial article
Selection
Japan's 100 Fine Castles No. 1Japan Castle Foundation
Visiting
Access
Partly open
Only two sites can be visited: Onnemoto Chashi and Notsukamafu Chashi No. 1 and No. 2. The other 22 are normally closed. Around Onnemoto there are private homes and kelp-processing yards; do not enter the fishing harbor or boat slipways. Roadside parking outside the designated lot is banned, and the city and tourism association warn that visits may be stopped if the rules are ignored. The sites are not cleared of snow in winter. The Japan 100 Castles stamp is at three places: the Museum of History and Nature, the Tourist Information Center next to Nemuro Station, and the Northern Territories museum at Cape Nosappu.
Too far to walk from the station. For Onnemoto, take the Nemuro Kotsu bus (Nosappu Line) to Nosappu-misaki and walk about 30 minutes (the tourism association also gives about 40 minutes, 2.7 km, one way from the Northern Territories museum). Notsukamafu is about 20 minutes by car from central Nemuro. The tourism association also suggests adding the chashi to a sightseeing taxi tour of Cape Nosappu.[9][10]
Checked: 2026-10-03
Hours and admission
Nemuro City Museum of History and Nature
Hours
9:30–16:30
Closed
Mondays (or the next day if Monday is a holiday), national holidays, and December 29 – January 3
Onnemoto: about 40 minutes from central Nemuro on Prefectural Road 35 (Okhotsk side), or about 10 minutes from Cape Nosappu; use the designated lot. Notsukamafu: about 20 minutes from central Nemuro on Road 35; parking for about two cars.[9][10][11]
Checked: 2026-10-03
Grounds opening hours
The chashi are outdoor sites; no official visiting hours are listed.Checked: 2026-10-03
Time neededEditors' estimate
Allow 20–30 minutes on site at each chashi. Seeing both and the museum takes about half a day by car.
Steps, slopes and footing
Grassland on coastal cliffs. Onnemoto and Notsukamafu have footpaths, but the surrounding cliffs are unfenced, so watch your step. Not cleared of snow in winter.[1][2]
Wheelchairs and strollers
Not confirmedChecked: 2026-10-03
Toilets and rest
Toilets at the chashi sites not confirmed
English signs / audio guide
English signage on site and at the museum is not confirmed. The tourism association has an English website.[9]
Seasons
The chashi are not cleared of snow in winter. The icharpa memorial ceremony is held at Nokkamappu at the end of September each year.[1][4]
Photography
Not confirmed
Works, closures and restrictions
Onnemoto Chashi: no parking outside the designated lot, and no entry to private land or boat slipways (Nemuro City and Nemuro Tourism Association, July 2022).[11]Checked: 2026-10-03
Suggested routes
Walk from Cape Nosappu to Onnemoto Chashi 120 min
Take the Nemuro Kotsu bus (Nosappu Line) from Nemuro Station to Nosappu-misaki
Collect the 100 Castles stamp at the Northern Territories museum
See the memorial to the Japanese who died in 1789, in front of the Hoppo-kan building
Walk to Onnemoto Bay (about 2.7 km, 40 minutes one way)
View the whole shape of Onnemoto Chashi from the harbor side, then climb the footpath
Walk back the same way to Cape Nosappu
Distance and one-way time are from the tourism association; the total is an editorial estimate. Buses are infrequent, so check the timetable first. Stay out of the harbor work areas and private yards.
A gravestone erected in 1812 for the 71 Japanese killed in the 1789 conflict, standing in front of the Hoppo-kan building at Cape Nosappu. A Nemuro City Tangible Cultural Property.[1][4]
A National Historic Site in Nishihama-cho, Nemuro, where the hollows of pit dwellings from the Satsumon culture crowd a terrace like craters on the moon.[2]
Checked: 2026-10-03
Editors' guide
An editorial guide based on sources and confirmed information — not a first-hand visit report.
Who will enjoy it
For 100 Castles collectors starting at number one, anyone interested in Ainu history, and lovers of wide views of sea and grassland. If you expect a keep or stone walls you will be surprised; go to see something quite different from a mainland castle.
What makes it interesting
What you are looking at is the shape of the earth. At Onnemoto, view the rounded mounds from the harbor side before you climb, and it becomes easier to see how the ditches divide them. At Notsukamafu, notice the depth of the half-round ditches along the cliff edge and the Sea of Okhotsk beyond.
Before you go
Only two sites are open, and both are far from town. Buses are infrequent, so a car or sightseeing taxi is the practical choice. Onnemoto is right next to homes and fishing work areas: use the designated lot and keep out of the way of people working. The sites are not cleared of snow in winter.
Ways to enjoy it
See the finds and diorama at the Museum of History and Nature first, and the bumps in the grass start to look like something people made. The city's drone relief maps and videos are also worth watching beforehand. At the Nokkamappu headland, remember that this is also where the 1789 conflict came to its end.
Photos
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Open questions
Nemuro City pages give the number of chashi sites in the city as either 32 or 30. The designated National Historic Site covers 24.
The chashi are dated roughly to the 16th–18th centuries, but exact dates are unknown. Their uses (forts, ceremonies, lookouts, negotiations) varied from site to site and cannot be reduced to one.
The Japan Castle Foundation's list classifies the site as a yamajiro (mountain castle), but the chashi are ditched enclosures on coastal cliff-top terraces with an entirely different origin, so this article does not assign a terrain type.
The city gives 2006 as the year of selection as a top-100 castle, while the tourism association says 2007. The Japan Castle Foundation announced the list in February 2006 and started the stamp rally in 2007.
The account of Tsukinoe and Nochikusa building chashi during the 1789 conflict comes from a record compiled in 1798; which, if any, of the Nemuro Peninsula sites these were could not be confirmed.
Toilets and accessibility at the chashi, admission to the Northern Territories museum, English signage on site, and photo rules could not be confirmed.
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