Hi, this is Ai.
If you follow the coastline south from Ise, past Toba, the land begins to fray at its edges. Peninsulas reach out, inlets bite deep, and the sea threads inland between low green hills. This is the Shima Peninsula, and the largest of those drowned valleys is Ago Bay (英虞湾, Ago-wan). It looks calm and a little sleepy — but this quiet water is where an entire global industry was born. Almost every cultured pearl you have ever seen traces back, in some sense, to these inlets.
I wanted to write about it because pearls are easy to think of as jewellery and nothing more. Down here, they are closer to farming: rafts, ropes, tides, and a lot of patience.
A coastline shaped for oysters
The first thing to understand about Ago Bay is its shape. It is a ria coastline — a landscape of ridges and valleys that sank until the sea flooded the low ground, leaving a maze of narrow, sheltered inlets. From above it looks less like a bay and more like a hand with many fingers.
That shape turns out to matter enormously. The inlets break up wind and waves, so the water stays gentle even when the open Pacific is rough. Rivers and forested hills feed nutrients in, the tides flush the bay, and the water temperature sits in a comfortable range for much of the year. Plankton — the food supply — is plentiful. For a creature that spends its whole life filtering seawater and cannot move, these are close to ideal conditions.
The creature in question is the Akoya oyster (akoyagai), a modest pearl oyster only a few centimetres across. Left alone, it occasionally produces a natural pearl, but far too rarely to build anything on. The story of Ago Bay is really the story of how people learned to coax that rare accident into happening on purpose.
My grandfather has a dry way of putting it: “People think the pearl is the miracle. The real miracle is that anyone had the patience to wait for the oyster.” He grew up hearing the Shima coast described as pearl country, and I think that framing stuck with me.
Kokichi Mikimoto and the first cultured pearl
The name attached to this history is Kokichi Mikimoto (御木本幸吉, 1858–1954), the son of an udon shop family in Toba. According to accounts kept by Mie Prefecture and the Mikimoto Pearl Island museum, he began experimenting with pearl cultivation around 1888, when he and his wife Ume opened a pearl-oyster farm at the Shinmei inlet on Ago Bay.
The early years were brutal. Red tides wiped out his oysters, money ran out, and success stayed just out of reach. Then, in July 1893, he found a small semi-spherical (hemispherical) pearl clinging to the inside of an oyster shell — the first cultured pearl in the world. He received a patent for the method of producing these half-domed pearls (known as mabe) in 1896.
I want to be careful here, because the history is often flattened into a single heroic moment. A fully round cultured pearl — the kind most people picture — came later and is a more tangled story. The technique for whole spherical pearls is usually credited to work in the early twentieth century by several people, including Tatsuhei Mise and Tokichi Nishikawa, whose independent methods were later reconciled with Mikimoto’s own patents. So it is fairer to say the round pearl had several parents than to hand it to one inventor. Where accounts disagree on exact dates and sites, I have tried to note it rather than smooth it over.
What is not in dispute is the outcome: Ago Bay and the surrounding waters of the Shima Peninsula became the centre of a new industry, and Japan became the source of the world’s cultured pearls.
Source: Chi King, Wikimedia Commons / CC BY 2.0
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How a cultured pearl is actually made
Here is the part that surprised me most, because it is so much more hands-on than I expected.
Cultivation begins with a tiny surgery. A small bead — traditionally cut from the shell of a freshwater mussel — is inserted into the oyster’s body together with a scrap of mantle tissue from a donor oyster. If the oyster accepts the intruder rather than rejecting it, its mantle tissue begins wrapping the bead in layer after layer of nacre, the same substance that lines the inside of the shell. That layered nacre is the pearl.
Then comes the waiting. The seeded oysters are hung from rafts on ropes, lowered into the bay, and tended for months or years — cleaned of barnacles and algae, moved to warmer or cooler water as the seasons turn, watched for disease. Water temperature, plankton levels, and typhoons all shape the final result. Only a fraction of oysters produce a pearl worth selling, and fewer still produce one of real beauty. It is agriculture with a very long, very uncertain harvest.
Historically, much of the diving and tending was done by women. The ama free-divers of the Shima and Toba coast, long famous for gathering shellfish and seaweed, were part of the early pearl world too — a connection I only touched on here, since it deserves its own article. If you are curious, I wrote separately about the ama divers of Toba.
From a quiet bay to the world’s jewellery boxes
Growing the pearl was only half the battle. Selling it turned out to be its own long struggle, and this is the part of the story that actually explains why Ago Bay reshaped a global industry rather than just a local one.
For most of history, a pearl was precious precisely because it was an accident — a natural pearl might be found in one oyster among thousands, which is why they were priced like gemstones. When Mikimoto’s cultured pearls reached the market, some jewellers and buyers abroad reacted with suspicion, arguing that a pearl grown on purpose was somehow not a “real” pearl at all. There were disputes, and even court cases in Europe, over whether cultured pearls could honestly be sold as pearls.
The resolution, broadly, was scientific: a cultured pearl is made of the same nacre, laid down by the same living oyster, as a natural one — the difference is only the nudge that started it. Once that was accepted, the economics changed completely. A gem that had been the preserve of royalty could now be produced in reliable quantities, in matched sizes and colours, at prices that ordinary people could eventually reach.
According to Mikimoto company history, part of the strategy was education: opening a boutique in Tokyo’s Ginza district where staff explained to customers exactly what a cultured pearl was and how it was grown. Japanese pearls went on to appear at international exhibitions and to travel out to jewellers around the world. I find it a little dizzying to stand above these sleepy inlets and remember that the strings of pearls in shop windows on the other side of the planet all descend, one way or another, from an idea tested right here.
Standing at the edge of the bay
When I visited, what struck me was how ordinary the scene looks. From a viewpoint above the inlets you see dark rafts strung out across the water in neat lines, small boats moving between them, and the wooded fingers of land folding into haze. There is nothing glittering about it. The glamour of a pearl necklace and the muddy, salty work of growing one feel like they belong to two different worlds — and yet they are the same world, separated only by time and a jeweller’s polish.
Source: kajikawa, Wikimedia Commons / CC BY 3.0
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My grandfather came down the coast with me that day. He is not sentimental about pearls, but he stood a long time looking at the rafts, and then said the thing that has stayed with me: that Ago Bay teaches patience better than any temple lecture, because the oyster does not care how much you want the pearl. You give it good water and good years, and sometimes it gives something back. I laughed — I had come for jewellery history and got a lesson about waiting instead. That is usually how outings with him go.
If you want to see it for yourself
Ago Bay sits at the southern end of the Shima Peninsula, roughly an hour or more by train and bus beyond Ise and Toba. The Kashikojima area on the bay is the usual base, with sightseeing boats that cross the inlets and viewpoints that catch the bay’s famous sunsets over the ria coast. Pearl-related museums and workshops in the region explain the cultivation process far more thoroughly than I can here, and some let you watch a pearl being lifted from an oyster.
I would not tell you a pearl is a thing you must buy — that is a matter of taste, and not what this bay is really about. But if you have time after visiting Jingu, riding out to Ago Bay reframes the whole coast. You stop seeing a pretty inlet and start seeing a quiet, patient kind of farming that happened to change the world. And if the light is good in the late afternoon, the sunset alone is worth the trip.
Historical details in this article draw on publicly available accounts from Mie Prefecture tourism sources and the Mikimoto Pearl Island museum. Where the record is uncertain — particularly the exact sites and dates of the earliest experiments, and the shared credit for the round cultured pearl — I have tried to flag it rather than state it as settled fact.