Oyamazumi Shrine on Omishima｜Were the Mountain God and the Sea God Not Separate?

The Seto Inland Sea flows on, calm and quiet, as if time had stopped. The Akashi Kaikyo Bridge joins Hyogo to Awaji Island, the Seto Ohashi Bridge joins Okayama to Kagawa, and the Shimanami Kaido joins Hiroshima to Ehime. With their opening, traffic across the sea has become brisk.

I have visited the Seto Inland Sea region countless times, and whenever I travel the Shimanami Kaido, there is one island I always stop at. It is Omishima, my grandmother’s home. Omishima is among the largest of the islands in the Seto Inland Sea, and in ancient times pirates and the sea peoples had their strongholds around here. It is hard to imagine from the gentle scenery of today, but in Japanese history this sea route was the most dangerous, and controlling it was directly tied to the power of the imperial court, which was in effect based in the Kansai region.

When the famed Taira no Kiyomori abandoned Heian-kyo and moved the capital to Fukuhara-kyo, from Hirano in what is now Hyogo Ward, Kobe, to the area around Yukimi Palace, declaring a new capital for Japan, one of his main aims was to take hold of the Seto Inland Sea route. He meant to cut off the goods and privileges flowing to the imperial family and nobles of Heian-kyo and concentrate power in the Taira clan.

The plan for the new capital collapsed and the court returned to Heian-kyo, but in that age the Kansai region in particular was thrown into violent turmoil, and people trembled in fear and lost their senses, believing that the Latter Days of the Law had arrived. When I look at Japan today, it is that age that comes to mind.

Now, every time I visit Omishima, there is a shrine I always pay my respects at. It is Oyamazumi Shrine. It is one of the ancient shrines recorded in both the Kojiki and the Nihon Shoki, but at some point I began to feel puzzled by something. The god enshrined at Oyamazumi Shrine, the guardian of this island, is Oyamatsumi, a god of mountains.

Thinking about it plainly, Omishima is an island floating in the Seto Inland Sea. Why is a god bound up with mountains enshrined here? Moreover, this shrine is the head shrine of the Oyamazumi and Mishima shrines venerated all over the country, which means this faith began on Omishima. From an island off the coast of the Seto Inland Sea, the source of mountain-god worship was born and then spread across the nation.

I could not solve this riddle however many times I visited the shrine, but when I turn time back to the distant past, it becomes clear that Omishima was once an entirely different world.

It was a mountain.

Long ago, before sea levels rose with the Jomon transgression, from roughly 80,000 to 15,000 years ago, the Seto Inland Sea did not exist and is thought to have been a vast grassland connected to the mainland of Honshu. More than on the Shimanami side, on the way across the Seto Ohashi Bridge to Kagawa, what meets the eye is less a scattering of countless small islands floating in the sea than the shape of ancient mountains.

A calm sea spreads out as if threading through the gaps between mountains. When you land in Kagawa, you come across a landscape where small, beautiful mountains rise one after another, and this landscape may be a remnant of the primeval age.

So if we trace the worship of Oyamazumi back to its origin, we can say that this sensibility came to dwell in the form of a “mountain god.” Even after the Seto Inland Sea took shape through the Jomon transgression, Omishima, now an island, remained the matrix of the mountain god, a history I find quite fascinating. And to me, this faith seems to have set other gods spreading as well. The gods of Japan cannot be pinned down as one; they appear in many layers of time, embracing every kind of layered interpretation.

In fact, a fragment of the Iyo Province Fudoki records that the god who dwells on Mishima is named Oyamatsumi, also called the Great God Watashi. “Wata” is also an ancient word for the sea, and this god has been worshipped as a god of the great ocean and of voyaging. In the world of the Kojiki and the Nihon Shoki, Watatsumi appears separately from Oyamatsumi. This suggests that “wata” was, in the earliest times, some concept connected to the sea, and personally I think that the god of the mountains and the god of the sea may not have been separate.

The fragment also tells that the god Oyamatsumi came across the sea and settled first at Mishima in Settsu Province, and was later invited to Iyo Province. That Settsu Mishima is identified with Mishima Kamo Shrine in Takatsuki, Osaka, and if you travel west around the Shikoku side from Omishima, you find many legends of crossing the sea that sound like nothing but a telling of ancient times.

I still do not understand it myself, but I believe the key lies in “Iyo no Futana Island” of the creation myth of the birth of the islands, and in the ancient expression “unabara,” the great sea plain. I am gradually beginning to dive deep.

The god of the sea and the god of the mountains. When we turn our eyes to this rift, we come one step closer to the sensibility of those who came before us.