CastleSea castle (umijiro)Next 100 Fine Castles No. 178
What makes this castle distinctive
A tiny island ringed by swirling tides was, in its entirety, the castle of the Murakami pirates.
Why?
Noshima Castle is a sea castle (umijiro) that used the whole of Noshima island, plus the neighboring islet of Taizakijima, off Miyakubo on Ōshima in Imabari. The waters around it are a notorious hazard where fierce tidal currents swirl, and the Noshima Murakami, who knew those tides better than anyone, made it their base. Holes cut into the rocks to moor boats still survive, giving it a look unlike any castle on land.[7][9][10]
The waters around Noshima (the Miyakubo Strait), reached on the tide-watching boats that leave from in front of the Murakami Kaizoku Museum.
What to look at
The water boiling up and swirling where it meets the island's rocks.
Why it's interesting
In the narrow straits of the Geiyo Islands, the rising and falling tide drives violent currents that have troubled sailors since ancient times. The Murakami, who could read these tides, offered piloting and escort to passing ships and controlled the Seto Inland Sea routes. Noshima, protected by these currents, was a natural fortress.[9][5][4]
Can you see it?
Visible from outsideSeen up close on the tide-watching boat (about 40 minutes; no sailings on Mondays). Kareiyama Observation Park also overlooks the island.
The shore of the boat harbor on the north side of Noshima, which served as the castle's main entrance (ōte).
What to look at
Holes drilled into the granite rocks (reef pits) and the flat, ledge-like wave-cut terraces.
Why it's interesting
The holes are thought to have held posts for mooring boats. They are features found only at a sea castle, where boats were the way in and out, and Imabari City says the shoreline remains at Noshima are well preserved. They are, however, being worn away by waves, including the wakes of passing ships.[8][10][6]
Can you see it?
Partly visibleSeen on a landing tour. Landing is not easy to arrange on your own; use the private Noshima Landing & Tide Cruise (check its calendar for sailing days).
Noshima Murakami family treasures at the Murakami Kaizoku Museum
Where
The Imabari City Murakami Kaizoku Museum in Miyakubo on Ōshima, facing Noshima.
What to look at
Items handed down in the Noshima Murakami family, such as a campaign coat said to have been worn by Murakami Takeyoshi and Kagechika, and a black-laced dōmaru armor (an Imabari City cultural property).
Why it's interesting
The family's heirlooms show that the Murakami were not mere raiders, but guardians of safe passage and cultured people who enjoyed tea and linked verse. Seeing them before you go out to the island changes how you look at it.[1][9]
Can you see it?
Visible from outsideAdmission 310 yen. Closed Mondays (or usually the next day after a holiday). Displays may change.
At a glance for visitors
Nearest station
1 min walk from Murakami Suigun Hakubutsukan bus stop
Climb
No climb
Time neededEditors' estimate
About an hour for the museum and about 75 minutes for the landing cruise: allow half a day.
Admission
310 yen; students 160 yen (groups of 20+: 250 / 130 yen)
Hours
9:00–17:00
Access
Partly open
Noshima is an island with no bridge. To land, use the private Noshima Landing & Tide Cruise (Setouchi Shimanami Leading). To see the island and its currents up close without landing, take Noshima Suigun's tide-watching boat (about 40 minutes). For a view of the whole island, go to Kareiyama Observation Park. The Next 100 Castles stamp is at the first-floor reception of the Murakami Kaizoku Museum, for visitors who have taken the landing cruise, the tide boat, or seen the permanent exhibition (per the 2018 notice). On museum closing days (except New Year), it can be stamped at Miyakubo Community Center (8:30–17:00).
Noshima is a small island in the Miyakubo Strait, just off Miyakubo on Ōshima. The Geiyo Islands' waters look calm, but in the narrow straits the tide creates violent currents. Surrounded by them, Noshima Castle was a natural fortress.[9][10][6]
02
Historical record
Three Murakami families
The Murakami pirates appear in history in the 14th century. Three families on Innoshima, Noshima and Kurushima all used the Murakami name, and each built sea castles. The Innoshima Murakami controlled the route on the Honshu side, the Noshima Murakami the shortest route through the middle, and the Kurushima Murakami the Shikoku side; acting as maritime checkpoints, together they controlled east–west traffic on the Seto Inland Sea. Noshima Castle is dated to the mid-14th century or later; its builder is unknown.[9][11]
03
Historical record
"The greatest pirates in Japan" sold safe passage
In the Warring States era, the missionary Luís Fróis called the Murakami "the greatest pirates in Japan." When his ship asked for safe passage, they handed over a silk flag bearing their crest and a signature, a pass later known as a kasho senki. With such flags and their pilots, the Murakami protected ships and charged tolls in return.[9]
04
Historical record
Baileys and shoreline remains
Noshima holds baileys called the Honmaru, Ninomaru, Sannomaru, Tōnan Demaru and Yabitsu, plus a flat area in the south, while neighboring Taizakijima has the Taizaki Demaru. The bailey slopes are cut steep. The boat harbor on the north side was the castle's front entrance, and shoreline features the pirates used, such as mooring holes and wave-cut terraces, survive. Excavations have found the only foundation-stone building in the castle, in the Sannomaru, along with traces of blacksmithing.[8]
05
Historical record
Protecting the site from rain, cherry roots and waves
Noshima Castle was designated a National Historic Site in 1953, and Imabari City has excavated it since 2001. Heavy rains in 2018 and 2020 caused landslides on its slopes, and the roots of cherry trees planted on the baileys were found to be damaging the buried remains. The city adopted a conservation plan in 2020 and a site improvement plan in 2021, which call for removing the cherry trees, draining rainwater, and rebuilding the landing so visitors can come ashore more easily.[13][7][8]
The Japan Castle Association lists no keep. It was a medieval sea castle without one.
The site today
The whole of two uninhabited islands, Noshima and Taizakijima, is the historic site. No buildings remain, but baileys, steep cut slopes, mooring holes and wave-cut terraces survive. There is a landing and toilet on the southern flat area and a shelter in the Sannomaru (to be rebuilt under the improvement plan).
Leveled baileys and steep slopes survive; parts of the slopes collapsed in heavy rain.[8]
Site only
Reef pits and wave-cut terraces
On the shore, including the northern boat harbor; being eroded by waves.[8][10]
Key facts
Type
Castle
Setting
Sea castle (umijiro)faces the sea, often with seawater moatsEditorial article
Period
Medieval (c.1185–1570s)Editorial article
Keep (tenshu)
No keep was builtthe castle never had a keepEditorial article
Main lords
Murakami clanJapan Castle Foundation
Remains to see
Baileys / enclosures (kuruwa)Editorial article
Designation
National Historic Site (Noshima Castle ruins) (1953)Editorial article
Selection
Next 100 Fine Castles No. 178Japan Castle Foundation
Visiting
Access
Partly open
Noshima is an island with no bridge. To land, use the private Noshima Landing & Tide Cruise (Setouchi Shimanami Leading). To see the island and its currents up close without landing, take Noshima Suigun's tide-watching boat (about 40 minutes). For a view of the whole island, go to Kareiyama Observation Park. The Next 100 Castles stamp is at the first-floor reception of the Murakami Kaizoku Museum, for visitors who have taken the landing cruise, the tide boat, or seen the permanent exhibition (per the 2018 notice). On museum closing days (except New Year), it can be stamped at Miyakubo Community Center (8:30–17:00).
Murakami Suigun Hakubutsukan bus stopFrom Imabari Station, change at Ishibunka Undō Kōen to the island bus (Shitadami Port–Miyakubo–Hayakawa/Tomoura line), about 8 minutes
about 1 min walk · No climb
About 1 minute on foot from the stop to the boat departure point. Buses on the Matsuyama–Ōmishima line do not stop at Ōshima Eigyōsho (Miyakubo), so change at Ishibunka Undō Kōen.[5][2]
Checked: 2026-10-04
Hours and admission
Imabari City Murakami Kaizoku Museum
Hours
9:00–17:00
Closed
Mondays (usually the next day if Monday is a holiday), December 29 – January 3
Admission
310 yen; students 160 yen (groups of 20+: 250 / 130 yen)[1][3][4][12]
Checked: 2026-10-04
Noshima Suigun tide-watching boat (no landing)
Hours
Hourly departures 9:00–15:00 (last at 15:00), about 40 minutes
Closed
Mondays (or the next day if Monday is a holiday) and December 31 – January 3
Admission
1,800 yen; elementary students 1,000 yen; younger children free. 100 yen off per person for groups of 15+[5]
Mainly weekends and holidays, about 75 minutes. Check the operator's calendar for times and dates (web booking up to 3 days ahead; minimum 10 passengers).
Closed
Per the operator's calendar
Admission
Adults 3,000 yen; junior/senior high 2,200 yen; elementary 1,700 yen; preschool 500 yen (includes a castle seal for landing passengers)[6]
Checked: 2026-10-04
By car / parking
About 3 km from Ōshima-kita IC (coming from Honshu) or about 10 km from Ōshima-minami IC (coming from Imabari/Shikoku) on the Nishiseto Expressway (Shimanami Kaidō); both are half interchanges, so mind your direction. Free museum parking for 50 cars and 3 buses; the boat departure point has 50 car and 10 bus spaces.[2][5]
Checked: 2026-10-04
Grounds opening hours
Landing is possible on the cruise when it operates; whether individuals may land independently could not be confirmed officially.[6]Checked: 2026-10-04
Time neededEditors' estimate
About an hour for the museum and about 75 minutes for the landing cruise: allow half a day.
Steps, slopes and footing
On the island you walk on paths. The bailey slopes are very steep, so keep away from the edges.[8]
Wheelchairs and strollers
No official information found. Landing involves getting on and off a boat.Checked: 2026-10-04
Toilets and rest
There is a toilet on Noshima's southern flat area (to be renovated under the improvement plan).[8]
English signs / audio guide
The official Japan Heritage "Murakami Kaizoku" website has an English version. English signage on site could not be confirmed.[9]
Seasons
Not confirmed
Photography
Not confirmed
Works, closures and restrictions
Imabari City plans conservation and improvement work from 2022 onward, including removing cherry trees, drainage, and rebuilding the landing and paths. Accessible areas may change as work progresses. Check the operator's calendar for landing cruise dates.[8][6]Checked: 2026-10-04
A lookout built for viewing Noshima Castle, about 10 minutes by car from Miyakubo Community Center.[4][7]
Checked: 2026-10-04
Editors' guide
An editorial guide based on sources and confirmed information — not a first-hand visit report.
Who will enjoy it
Good for anyone who wants to see a castle defended by the sea and tides rather than walls and keeps, fans of Murakami pirate history, and travelers cycling or driving the Shimanami Kaidō.
What makes it interesting
Start at the museum to learn how the Murakami lived and how their flag passes worked, then feel the whirlpools around the island on the tide boat. If you can land, look for the mooring holes in the rocks of the northern boat harbor to picture a castle entered by boat.
Before you go
The landing cruise runs mainly on weekends and holidays and needs advance booking with a minimum group size. To get the stamp you need to have used the landing cruise or tide boat, or seen the permanent exhibition (per the 2018 notice). Ōshima's two interchanges are half interchanges, so the exit depends on which way you come from.
Ways to enjoy it
Paying attention to the tide times before you board helps you notice how the current's direction and speed change. On land, look down from Kareiyama Observation Park at the island and its currents, and you'll see at a glance why the pirates chose it.
Photos
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Open questions
Who built Noshima Castle, and when, is unknown; the Japan Castle Association says the mid-14th century or later.
The landing cruise is run by a private company, and the operating period shown on its page may be out of date. Whether individuals may land on their own could not be confirmed officially.
The stamp conditions come from a 2018 notice; check whether they still apply.
Some photos date from 2016, when cherry trees still grew on the baileys; the improvement plan calls for removing them.
さかおりCC BY-SA 4.0Wikimedia Commons
