“Donated by Minamoto-no-Yoshitsune in the 1100s.” I paused and reread the placard. Here in front of me, in this aging concrete block of a building that also reeked of mildew, was a weapon offered in hopes of securing military success nearly a thousand years ago by one of history’s heroes. Right next to it sat a naginata said to have been gifted to the shrine by none other than the warrior monk Benkei. Looking around at all the other arms crammed into the small room, Minamoto-no-Yoshitsune and Benkei were hardly outliers. Nearby, there were donations tied to figures like Hojo Tokimune, too. What was oddly lacking was the ever-watchful staff you’ll find at stuffier museums in the big city.
On that note, allow me to introduce Oyamazumi Shrine. Located on the island of Omishima, this Shinto sanctum has existed since ancient times. Officially the head shrine of the former Iyo Province, as well as of all 10,000 Yamazumi and Mishima shrines scattered across Japan, Oyamazumi Shrine is one of those extremely important spots that paradoxically few foreign tourists have ever heard of. The epic shrine grounds sit at the western foot of Omishima’s highest peak, Mt. Washigatou, which is considered a sacred mountain. Historians estimate Oyamazumi Shrine to be over 2,600 years old based on the old camphor tree, but since it predates written records, the truth is anyone’s guess.
In terms of this deity and shrine, Oyamazumi Shrine enshrines Oyamazumi-no-Okami (henceforth just Oyamazumi), the ancient kami of mountains. The Shinto pantheon is not a tidy family tree in which every deity descends from Amaterasu Omikami, and Oyamazumi appears in the Kojiki before the sun goddess enters the story. Born from Izanagi and Izanami during the creation of the natural world, Oyamazumi belongs to an older generation of kami tied to elemental forces. The two divine lines later intersected through Oyamazumi’s daughter, Konohanasakuya-hime, who married Amaterasu’s grandson Ninigi-no-Mikoto. Out on Omishima, Oyamazumi also came to be worshipped as a god of the sea and safe passage.
What really sets Oyamazumi Shrine apart, though, is its treasure hall, which is said to contain roughly 40 percent of all the arms and armor in Japan that are designated as either National Treasures or Important Cultural Properties. The collection includes eight National Treasures and hundreds of Important Cultural Properties, many associated with some of the biggest names in Japanese military history. Alongside Minamoto-no-Yoshitsune, Benkei, and Hojo Tokimune are artifacts tied to the likes of Tomoe Gozen and Kono Michiari. All of this is packed into a hulking reinforced-concrete building erected in 1926, a fireproof monolith that looks more like an old municipal archive than one of the country’s great repositories of samurai history.
Inside, the contrast only gets more absurd. Priceless weapons and armor were jammed into glass cases that looked untouched for decades, and truth be told, that is a huge part of the allure. Without the stifling gaze of a middle-aged woman that makes you afraid to even breathe near the glass (as there would be somewhere like the Tokyo National Museum), the entire setup felt so laughably lax that I could not stop thinking about the shuttered windows. It was almost like someone could force one open, walk away with a piece of history, and be halfway across Omishima before anyone noticed. I am sure that is not actually the case, but talk about a high-trust society!
Naturally, I can’t say whether that theory would actually work, nor did I have any intention of testing it (though my friends at Setouchi DMO and I couldn’t stop joking about it in the car afterwards). What I can say is that you definitely need to drop by Oyamazumi Shrine when exploring the Shimanami Kaido. Most people view this route as a straight beeline across multiple islands from Onomichi to Imabari City, but there is an incredible amount of culture hiding along the way. Chief among these stops is this seemingly secret Shinto shrine that just happens to house nearly half of Japan’s nationally designated arms and armor.
How to Get There
A quick word on travel logistics. As noted, Oyamazumi Shrine is located on the island of Omishima, one of the isles along the famed Shimanami Kaido connecting Onomichi in Hiroshima Prefecture with Imabari in Ehime Prefecture on Shikoku. Alas, the shrine sits over on the western coast of Omishima and requires quite the detour from the standard cycling route. That said, it is just one more reason why it is critical to take the Shimanami Kaido slowly rather than treating the route like a race and sprinting from one end to the other.
For those of you who are not cycling across the Shimanami Kaido, a rental car is the easiest way to get to Oyamazumi Shrine. That said, buses do connect Imabari with the shrine, while travelers coming from the Honshu side can take a highway bus to Omishima and transfer from there. These services are nowhere near as frequent as the trains and buses found in Japan’s major cities, though, so you will definitely want to plan well in advance. Traveling through the Japanese countryside is a different beast altogether, but it can still be done if you are willing to put in the effort.
For trains, I always use Jorudan, but when it comes to buses, I find Google Maps to be much more helpful. In either case, plan your movements well in advance and make absolutely sure you know when the final bus departs. You do not want to end up stranded on the Shimanami Kaido with no way back to Honshu or onward to Imabari. Likewise, if you are cycling, be honest with yourself about both your physical abilities and how much time the detour will require. Oyamazumi Shrine is absolutely worth the added distance, but only when you have left yourself enough time to actually enjoy it.
Exploring the Oyamazumi Shrine Grounds
As soon as you come across the shrine grounds, the first thing you’ll be greeted with is the gate, where two imposing guardian figures stand on either side. At first glance, they resemble the Nio guardian statues commonly found at Buddhist temples, but they are actually armored zuijin, the traditional protectors of Shinto shrines. The resemblance is understandable given how thoroughly Shinto and Buddhism blended together under Shinbutsu Shugo over the centuries. Unlike the seated court nobles found at many shrines, though, these two stand armed and ready for battle.
Beyond the gate, the next thing that commands your attention is the enormous camphor tree in the center of the grounds. Said to be around 2,600 years old, this ancient specimen is one of the main reasons Oyamazumi Shrine claims such a staggering age. It is hardly alone either. Roughly 200 old camphor trees surround the shrine, including another allegedly closer to 3,000 years old. Together, the grove has been designated a National Natural Monument and lends the entire sanctuary an appropriately ancient atmosphere.
As is always the case with early Japanese history, this is also where things start to get quite murky. A surviving fragment of the old Iyo-no-Kuni Fudoki preserves a tradition that worship of Oyamazumi was brought to Japan from the Korean kingdom of Baekje before eventually taking root on Omishima. That story is impossible to verify and should be treated as legend rather than settled history. Still, Baekje maintained close political, cultural, and religious ties with the early Yamato court, so the possibility is not entirely outlandish.
One of the problems with dealing with places this old is that written records are extremely scarce. Chinese writing reached Japan from the continent during the early centuries of the common era, while Japan’s major surviving chronicles were not compiled until the eighth century. That leaves much of the country’s earlier history to be reconstructed through archaeology, foreign accounts, local traditions, and educated guesswork. Somewhere in that haze, Oyamazumi Shrine rose into the head shrine of Iyo Province along one of the Seto Inland Sea’s most important maritime routes.
Regardless, the shrine has been under the care of the Ochi clan for well over a millennium. Shrine tradition holds that Ochi Yasumoto became its first hereditary chief priest in 708, after which his descendants oversaw both the rituals and management of Oyamazumi Shrine. The family eventually adopted the priestly title Ohori as its surname and later became known as the Mishima family. This was hardly a ceremonial role either. As both priests and local power brokers, the clan became deeply entangled with the warriors and maritime forces controlling the Seto Inland Sea, helping Oyamazumi Shrine grow into one of the most politically important religious institutions in Iyo Province.
Anyway, from there, continue deeper into the grounds and you’ll eventually reach the main shrine area. The present main hall dates to 1427 and, together with the worship hall, is designated an Important Cultural Property. This is where visitors can formally pay their respects to Oyamazumi. Despite everything waiting inside the treasure hall, it is worth remembering that Oyamazumi Shrine is not merely a museum with a religious complex attached. The worship came first, and the collection exists because generations of warriors believed Oyamazumi could influence whether they returned home alive.
Evidence of that martial devotion is scattered throughout the grounds. Look up into the rafters and you’ll find old group photographs of military cohorts who came here to pay their respects, including men connected to the Imperial Japanese Navy in nearby Kure. These are easy to overlook beside the ancient trees and historical buildings, but they show that the shrine’s military associations did not disappear with the samurai. Soldiers, sailors, and martial artists continued visiting Oyamazumi Shrine well into the modern era.
Oyamazumi Shrine’s Treasure Hall
No visit to the shrine would be complete without dropping by the treasure hall mentioned in the opening anecdote. As noted above, Oyamazumi Shrine has long been a place where warriors from across Japan came to pray for victory or offer up their weapons afterward in gratitude. The result is a collection holding an outsized share of the nation’s designated armor, along with a ridiculous number of swords, naginata, helmets, and other martial artifacts, many donated by some of the biggest names in history over the centuries of the shrine’s existence.
The treasure hall is divided between two connected buildings. The first is the aforementioned three-story reinforced-concrete monolith, known as the Kokuho-kan, which was erected in 1926. Its first floor contains blades associated with some of the heaviest hitters in Japanese history, including Minamoto-no-Yoshitsune, Benkei, and Hojo Tokimune. The second floor brings still more arms, armor, and other miscellaneous shrine artifacts, while the third contains additional swords alongside National Treasure armor traditionally attributed to Minamoto-no-Yoritomo and Minamoto-no-Yoshitsune.
A stairwell on the second floor leads into the adjacent Shiyoden, a later building whose exterior looks far more like it belongs beside a shrine. Inside are rows upon rows of armor packed into old wooden and glass display cases, including pieces connected to the Kono clan and the warrior Ohori Tsuru-hime. I could hardly believe how many nationally designated artifacts had been crammed into a single room. Rather than carefully isolating each suit as the centerpiece of its own gallery, Oyamazumi Shrine has so many priceless pieces of Japanese history that there is simply no alternative given the space.
One of the most mind-boggling items is the National Treasure bronze mirror traditionally said to have been donated by Empress Saimei around 13 centuries ago. During my visit, it sat in the middle of the Shiyoden in what looked like just another thoroughly ordinary case. By that point, though, the lack of fanfare had stopped feeling shocking and started feeling like the whole charm of the place, with priceless history sitting unbothered on rural Omishima as though it were nothing special at all. It’s truly hard to put into words, but you’ll get what I mean if you go.
Finally, the same ticket also grants access to the neighboring Omishima Maritime Museum, which takes the collection in an entirely unexpected direction. Emperor Hirohito was a serious marine biologist, and the museum was constructed around the Hayama Maru, a vessel used to collect specimens for his research. Alongside the boat are his scientific publications, marine specimens from around the Seto Inland Sea, and various maritime materials. After several rooms of swords and armor, suddenly finding an imperial research vessel devoted to marine biology is a bizarre final twist.
Oyamazumi Shrine & the Murakami Suigun
Before wrapping things up, there is one final piece of Oyamazumi Shrine’s history that deserves attention, namely its close relationship with the Murakami Suigun. These seafaring warlords dominated the waters around the Shimanami Kaido during Japan’s long age of civil war. Often described on this site as the “pirates of the Seto Inland Sea,” the Murakami Suigun were actually something closer to a loosely affiliated maritime dynasty that could raid ships, escort merchants, collect tolls, and serve as a navy for powerful daimyo depending on what the situation called for.
As mentioned before on this Japan travel blog, the Murakami Suigun consisted of three main families based around Noshima, Innoshima, and Kurushima. Though linked by blood and a shared maritime culture, each branch largely governed its own stretch of the Seto Inland Sea. The Noshima Murakami were arguably the most powerful, occupying a tiny island fortress positioned directly beside major shipping lanes. From there, they could monitor vessels passing through this part of the Setouchi region and decide who received safe passage, who paid a toll, and who was about to have a very bad day.
The Murakami Suigun’s power came from an intimate understanding of the waters around these islands. The Seto Inland Sea may look serene from the bridges above, but the narrow channels below contain fast-moving currents, whirlpools, and tides that change dramatically throughout the day. Outsiders could easily end up on the rocks, while the Murakami Suigun knew how to use the sea itself as a weapon. They were not merely pirates with boats. They were expert navigators and naval tacticians who turned local knowledge into an empire.
Naturally, the Murakami Suigun maintained close ties with Oyamazumi Shrine. Warriors and sailors who made their living on these treacherous waters regularly came here to pray for safe passage and victory. The Noshima Murakami even offered linked poetry known as horaku renga as ritual prayers and adopted the shrine’s crest as part of their own identity. For these maritime lords, Oyamazumi Shrine was not simply another religious site. It was the seat of their divine protector and a critical part of the spiritual infrastructure that supported their legitimacy, thereby allowing them to rule over the Seto Inland Sea.
As you might imagine, traces of their legacy remain scattered throughout the Shimanami Kaido. Over on Oshima, the Murakami KAIZOKU Museumexplains their history through excavated relics, documents, ship models, and exhibits overlooking the ruins of Noshima Castle. Farther north, Innoshima Suigun Castle explores the branch that controlled the waters closer to Onomichi. These sites are spread across several islands, which is yet another reason not to treat the Shimanami Kaido as a one-day sprint between two cities.
Other Nearby Attractions
As for Omishima itself, Oyamazumi Shrine is hardly the island’s only cultural attraction. There are several art facilities scattered around the coast, including the Omishima Museum of Art, the Tokoro Museum Omishima, the Ito Toyo Architectural Museum, and the Iwata Ken Mother and Child Museum. The buildings and views are often as much a part of the experience as the collections themselves. That said, most are well away from the standard cycling route, so anyone attempting the entire Shimanami Kaido under their own power may want to save them for a future trip by car.
Elsewhere along the route, one of the easiest major stops is Kosan-ji on Ikuchijima. This relatively modern Buddhist complex contains replicas inspired by some of Japan’s most famous historical buildings, a cave filled with Buddhist imagery, and the sprawling Miraishin-no-Oka marble garden pictured above. Unlike Oyamazumi Shrine, Kosan-ji sits close to the normal cycling path, making it a far easier addition for travelers keeping a close eye on time and tired legs. I have already covered the temple in detail elsewhere for anyone planning to drop by.
Once you finally reach Imabari, resist the temptation to immediately return the bike and hop on a train. The city is home to Imabari Castle, one of Japan’s unusual seaside fortresses, complete with a moat fed by seawater. It is also the center of the country’s towel industry, which is taken seriously enough to warrant an entire museum. Those with exhausted legs can instead head directly to Shimanami Hot Spring Kisuke-no-Yu and wash away the sweat accumulated while crossing the islands. I have a separate Imabari guide covering all of these options in greater detail.
Ultimately, there is far more to the Shimanami Kaido than blue cycling lanes and impressive suspension bridges. The route passes through islands shaped by pirates, warriors, ancient religious traditions, modern art, and some truly strange local museums. Oyamazumi Shrine is perhaps the best example of everything travelers miss when they make a straight beeline from Onomichi to Imabari. Take the Shimanami Kaido slowly, leave room for detours, and give the history beneath those spinning wheels the attention it deserves.
Until next time travelers…
