SHIMA, Japan — It was raining hard, with blustery winds roiling the sea — unusual conditions on the spring day when I visited the Mikimoto Tatoku Pearl Farm in this coastal city on Japan’s main island of Honshu.

But as the farm workers say, there is always strong wind right before the weather begins to clear up.

And Mikimoto is expecting a lot of figurative blue skies this year as it marks the 130th anniversary of the pearl culturing process, created by the brand’s founder, Kokichi Mikimoto. (The celebration is to include the introduction of a polyester pearl-stringing thread made entirely from plastic bottle fibers and “A Love Letter to the Sea,” a series of six short films.)

The Tatoku farm is where Mr. Mikimoto developed the culture process. His dream, as he reportedly told Emperor Meiji in 1905, was to “adorn the necks of all women around the world with pearls.” He lived here later, too, occupying a small wooden house named Shinju-kaku for several years before his death in 1954 at 96.

When I rode a boat across Ago Bay, I could see the house and its guesthouse on the top of a hill, and other wooden buildings lining the shore. They included two that the farm calls the factory, used to start the culturing process and for offices, and two more that it calls the pearl research institute, used for oyster breeding and research. (The farm is closed to the public.)

Floating on the bay’s surface nearby was a series of large platforms, grid-like structures that, underwater, held nets with thousands upon thousands of oysters, their pearls slowly developing.

The inspiration for cultivation began in the late 1800s, when the Akoya oysters in the Ago Bay region were being overharvested for their pearls. Mr. Mikimoto, who had begun his work life as a noodle vendor, feared they would become extinct. He learned the principles of natural pearl formation from a university professor and immediately began experimenting, trying to find a way to force production.

The anniversary marks 1893, when he first cultured a semi-spherical pearl; in 1896, when he could do it consistently, he established the Tatoku farm. “This region is suited for pearl harvest because of the enclosed sea, which means the water is calm,” Junya Yamamura, the farm and factory manager, said, referring to the bay. “It’s important because oysters need to rest, and there is a lot of nutrition.”

Mikimoto is one of the few high jewelry brands that does everything from creating its basic material to sales. Its pearl operations include another farm in Fukuoka prefecture, part of Japan’s southern island of Kyushu, and most of its pearl necklaces are assembled in Toba, another coastal town about 22 kilometers, or almost 14 miles, from Shima.

In 1899, Mr. Mikimoto opened the company’s first store, in Tokyo’s Ginza. Now, with reported sales of 25.8 billion yen ($192 billion) in 2022, the business has an online shop and 18 stores around the world, with many more points of sale in department stores and boutiques. Its necklaces start at about $3,300 and earrings and ear cuffs at about $300, and the company has expanded into gift items like silk scarves, acrylic and lacquer photo frames, and an eau de parfum with scents of iris and magnolia.

But cultured pearls continue to be its signature. The brand, which initially had to fight claims that its pearls were just imitations of the real thing, now is known globally as a premiere name in pearls — particularly in Japan, where girls commonly receive a strand as they come of age and wear it for special occasions throughout their lives.

Its most significant advance in decades came in early 2020, said Yasuhiko Hashimoto, managing director of the company’s sales and marketing division and chief executive of Mikimoto America. That’s when it introduced a collaboration with the avant-garde Japanese fashion brand Comme des Garçons.

“With Rei Kawakubo’s innovative vision to adorn men in pearls, together we successfully established a new culture; to adorn the necks of all, regardless of age or gender,” Mr. Hashimoto wrote in an email, referring to the designer and founder of Comme des Garçons. “What was once a symbol of wealth and prosperity, only accessible to men of royalty and nobility, has now become a gemstone of choice for modern men and women alike.”

Arrivals at the Met Gala earlier this month seemed to prove his point, with Brooklyn Beckham, Ashley Graham and the N.B.A. basketball star Shai Gilgeous-Alexander among the guests wearing Mikimoto — although they all were eclipsed when Rihanna turned up in them at an after-party.

From Oyster to Necklace

The star at the Tatoku farm is the Akoya pearl oyster, or Pinctada fucata martensii, a species of marine bivalve mollusk found in the waters surrounding Japan. “They’re not like the kind of oysters we eat,” said Mr. Yamamura, 54, although local residents do consume the oyster’s adductor muscle, the crescent-shape bit that keeps the shell closed.

The culturing process begins with breeding, but perhaps the main element is patience: It requires about seven years to go from a grain of sand to a softly glowing pearl in a piece of jewelry.

Some oysters selected from the previous breeding cycle are artificially inseminated and, in the large aquariums at the Tatoku farm’s research institute, produce babies called spats, tiny dots that are barely visible to the naked eye.

In about three weeks the spats grow to the size of a grain of rice, and most attach themselves naturally to a type of net, called a collector, placed in the aquariums; the ones that don’t get a bit of manual help. The spat-rich collector nets then are removed from the aquariums and lowered into the sea, attached to one of the floating platforms.

“As they keep growing, we transfer the oysters through different sizes of nets,” Mr. Yamamura said. Workers closely monitor their nutrition and, as they grow, clean their shells of debris like mud and barnacles.

After two to three years, the oysters are transferred from their net to a black plastic basket that has just a few small holes, limiting the amount of nutrition that can reach them for awhile so their metabolisms, particularly their gonads, are ready for the surgery that starts the culturing process.

Mr. Yamamura demonstrated the procedure in the empty factory area (the farm had scheduled my visit to view the mass surgeries, but by the time I arrived, it wasn’t quite ready). The idea of a surgical procedure made me think I was about to witness something a bit gory but, he said, “It’s more like a dental procedure.”

“Timing is key,” he noted, sitting at one of the factory work tables lined up against the walls of the long narrow room. A selection of oysters, their shells propped open slightly by blue plastic sticks called stoppers, were in a blue plastic tray on the table. There also were the same number of two-millimeter square bits of mantle tissue, taken from the bodies of oysters known to have produced beautiful nacre.

(Yasunori Iwahashi, manager of the farm’s research institute, said that nacre, the hard composite that makes up a pearl, is secreted naturally by mother oysters. “A foreign body has entered their system, so the mother oysters try to cover it because it’s harmful,” he said, which explains why nacre also is called mother-of-pearl. And its color — which can be pink, white, green or cream — depends on differences in the nacre.)

Mr. Yamamura placed one oyster on a vertical metal holder; the stopper was removed, but the shell was kept open with a clamp. With a scalpel in one hand and long tweezers in the other, he quickly inserted a piece of mantle tissue inside the gonad of the mother oyster and then a tiny bead made from the shells of freshwater mussels.

The key, he explained, was to insert the bead in a way that the tissue would adhere to it, becoming the nucleus of what eventually would be the pearl. An oyster can have more than one nucleus inserted at a time, depending on its size and the desired size of the pearls.

In less than a minute, Mr. Yamamura had finished and put the oyster back on the blue tray, where it closed its shell immediately, and he moved on to the next one. “You have to be quick and precise, so you minimize injury and don’t stress the oyster,” he said.

The surgeries usually are done in late spring by 20 to 30 seasonal workers, most of them women who have other jobs at the company factory in Toba for the rest of the year. “It requires precision and patience,” Mr. Yamamura said, adding that each worker usually does 500 to 600 shells a day.

“After the operation, the oysters go back in the water for 10 to 14 days to rest and heal in calm waters,” Mr. Yamamura said. “Unfortunately, some do not survive the surgery and die. The others are moved into nets attached under rafts in the bay, where they stay for one or two years, depending on their condition.”

After harvesting, which is done during the winter, farm workers sort the pearls according to their size, color, luster, shape and flaws. Only those of superior quality, about half of the usual harvest, are selected for use.

An Oyster Goes a Long Way

But what happens to all the oysters and the pearls that are rejected?

Mr. Iwahashi of the research institute, who has worked at Mikimoto for 34 years, said crushed oyster shells and useful components such as collagen and conchiolin that are extracted from organic waste are all provided to an affiliated company for use in cosmetics and dietary supplements.

Also, he said, the debris cleaned from the shells of growing oysters and unused oyster meat are used to make compost, which the company gives free to farmers as part of its zero-emissions program.

The institute, equipped with computers and microscopes, has a 12-member staff that, Mr. Iwahashi said, conducts “research on pearl cultivation, protection of the marine environment and countermeasures against red tides,” the proliferation of algae that can harm the oysters and cause other environmental damage.

In 2004, the institute developed what Mikimoto calls the world’s first organic water quality environment monitoring system, named Kai-Lingual. (Kai means shell in Japanese). Solar sensors placed in the bay detect red tides, oxygen deficiency and other sea abnormalities by analyzing shell movements in real time. “When the oysters start to open and close quickly, meaning they’re gasping for oxygen, it sends us a text message so we can take prompt measures to move the nets to safety,” Mr. Iwahashi said.

By midafternoon, as predicted, the sky cleared. Mr. Yamamura and I walked out on the floating platforms, which are made of cypress, called hinoki in Japanese, and are replaced every 10 to 20 years.

Beneath, there could be about 100,000 oysters in nets, but Mr. Yamamura said he did not know the exact number. “Back in the day, women divers called ama-san were hired to collect oysters, but nowadays we have a system of rafts and nets, no need to go underwater anymore,” he said.

There is no school to learn pearl farming techniques.

“I started working on the farm at 18 years old, and my father and grandfather also worked here,” said Mr. Yamamura, who, like most of the farm’s workers, lives in the area. “I learned from watching and practicing.”

Pearl production requires confidence, he said, as performing surgeries or drilling pearls for jewelry cannot be redone if a mistake is made. “You only get one shot,” he said. “You have to have a certain courage to commit yourself to do something you only get one shot at doing.”