Okamoto Soy Sauce

Okamoto Soy Sauce


One of the few remaining artisanal soy brewers on the western islands of the Seto Inland Sea, Okamoto makes a classic style of soy sauce that adds a touch of heartiness as well as a special taste-of-place flavor to the region’s traditionally light and ingredient-oriented home cooking.


Okamoto Soy Sauce is located on the northern shore of Osakikamijima Island in the Seto Inland Sea, a short walk from the island’s port of Tarumi. It was founded in 1932 when the islands of the Seto Inland Sea were major producers of food for the rest of the Japan. At that time, Osakikamijima was a large producer of salt—a key ingredient in making soy sauce. Salt was harvested from the surrounding sea using the enden salt-making method. Enden, or clay pans, along the island’s coastline were flooded by taking advantage of the sea’s extreme range of difference between high and low tides. The captured seawater was then concentrated through air and wind evaporation before being boiled down to create a minerally-tasting, sand-colored salt. The ruins of these enden salt fields can still be seen along the perimeter of the island.

The other key ingredients needed for making soy sauce—soy beans and wheat—were brought by ship from farms on mainland Honshu Island, and the finished soy sauce was shipped onwards to markets elsewhere, similar to the practice of other soy sauce brewers in the region. But unlike the brewers at Japan’s major soy sauce brewing center on Shodoshima Island to the east (such as Yamaroku Soy Sauce), who shipped their soy sauce to Tokyo and other points in northern Japan, Okamoto has always mainly served its regional market. It delivers the majority of its soy sauce to the big regional cities of Hiroshima and Osaka, and the flavor of its soy sauce is brewed to meet the needs of the Seto Inland Sea’s fresh, yet hearty cuisine.

Okamoto is a classic style of soy sauce, but has a medium rather than full body and a rich, yet straight-forward umami that allows the creamy flavors of its soy beans and wheat to come through. In addition, while not actually sweet, Okamoto soy sauce is less acidic than the types of classic style soy sauces brewed on Shodoshima for northern Japan’s rich, heavy cooking. Seto Inland Sea cuisine is characterized by fresh foods, natural flavors, and light cooking techniques. But unlike the classically refined cooking of Kyoto and its environs in the eastern half of the sea, dishes in Okamoto’s area are home-style and hearty; food cooked for the fishermen, farmers, and workers of the region. Okamoto is a perfect seasoning for this kind of cooking because it provides a burst of saltiness and just the right infusion of umami richness, depth, and flavor complexity.

Located on the northern side of Osakikamijima, Tarumi is a relatively quiet port these days, mainly servicing ferry boats and local fishermen. Mt. Kannonmine, the highest point on the island, can be seen in the distant background.

Located midway between the mainland islands of Honshu and Shikoku in the western half of the Seto Inland Sea, Osakikamijima is one of the largest islands among the more than 700 islands in the sea. After World War II, most of its old-time food making businesses were replaced by industrial activity, and its extensive shoreline was dotted with ship building and repair operations. These too are now almost completely shuttered, and the 8,000 people living on the island are re-asserting the island’s heritage as a producer of high quality foods. Farm Suzuki, located at the eastern tip of the island, has pioneered the farming of claire oysters in Japan, re-purposing an old enden salt-making field to raise delicately delicious oysters in a sheltered haven that combines fresh spring water and salty sea waters. Nearby is Nakahara Olive Grove, which started pressing it first all-natural olive oil this year. The island is also famous for its shiitake mushrooms and citrus, especially the beautifully fragrant and mild-tasting green and yellow lemons grown on Iwasaki Farm. The efforts of these food artisans and farmers benefit from the island’s mild climate and the fresh water flowing down the forested slopes of Mt. Kannonmine, one of the highest mountains in the Seto Inland Sea.

The Okamoto family has been at the forefront of the island’s culinary rejuvenation. It is one of the island’s oldest artisanal food businesses and has a direct, unbroken link back to the traditions of the founder. At one time, there were eleven soy sauce makers on Osakikamijima. Today there is only Okamoto. While the soy sauce is made by the third generation brothers, Yasufumi and Tetsuya, their octogenarian father Yoshihiro, the son of the founder, is also still very active at the brewery. He is a warm, welcoming presence to visitors. As Yasufumi points out, their father is also a living handbook to Okamoto’s century’s-old brewing know-how, which relies on the five senses of sight, sound, smell, touch, and taste.

Okamoto is a small operation, making an average of 50,000 liters of soy sauce a year in thirty large kioke wooden barrels. Some of the barrels are over 100 years old, having been passed on to Okamoto by brewers that have gone out of business. Every step of the brewing process is done by hand. The other key artisanal soy sauce-making practices the brothers follow are: the soy beans and wheat are domestic, the soy beans are whole, full-fat marudaizu beans, the beans and wheat are germinated and massaged for three days with koji-kin mold spores in a heated muro room, and the resulting moromi mash is fermented and aged for two years in a sea salt brine.

Within this broad framework, Yasufumi and Testuya use special ingredients and techniques to produce not only a uniquely-flavored soy sauce, as all artisanal soy sauces are, but one that reflects the culinary taste of the region. The soy beans are the Sachiyutaka hybrid, grown across the straits on the Yume Farm in the rich, agricultural highland valley of Shobara in Hiroshima prefecture. The soy beans are steamed for a quick seven minutes at a rapid increase in temperature to 105 degrees Celsius and then quickly cooled down to preserve their flavor and umami-producing proteins. The wheat is the Minami no Kaoru hybrid, also grown in the Shobara valley. It is roasted gently together with sand and then tumbled in a perforated drum so that most of the sand falls out. The bits of sand that remain add to the mineral content of the final soy sauce and its taste of place. The wheat is then cracked by a roller to a medium-sized coarseness, which Yasufumi knows is right by feel, and mixed with the soy beans in the muro room.

The water used to make the soy sauce is Hiroshima prefecture’s famously soft water. It is a tricky water to use for brewing, and requires a robust moromi mash and long, slow fermentation. (Hiroshima’s soft water and its special brewing requirements are well-known because of the prize-winning ginjo sakes they produce.) The large size of the cracked wheat grains is key to the soft-water brewing process for two reasons. They help create a robust moromi mash by catching more of the koji-kin mold spores during the germination process. They also ferment more slowly than smaller grains. Okamoto’s kioke wooden barrels are another important factor. They are unusually large for an artisanal soy sauce brewer. At 5,400 liters of soy sauce per barrel, they are, for example, 50% larger than the barrels used at Yamaroku Soy Sauce. The larger the barrel, the slower the fermentation. The Okamoto brothers carefully manage the slow fermentation by mixing the moromi mash every day for thirty minutes using long bamboo poles.

When brewed right, as it is at Okamoto, soft water produces an aromatic, mild, and subtly complex soy sauce—a salty, umami-rich counterpart to the fragrant, delicate ginjo sakes produced by soft water. The final step in making Okamoto’s lighter-bodied type of classic soy sauce is the way the brothers extract the soy sauce from the moromi mash. For their highest grade soy sauce, they slowly drip the soy sauce from the moromi through bags for about a week and only then press it very lightly. For their regular grade soy sauce, they press the moromi overnight. For both types, they siphon off the bean and wheat oils floating on the surface using a relay system of pipes they have devised that relies on natural gravity. Removing this excess oil enhances the clarity, lightens the body, and preserves the nuanced flavor of Okamoto’s soy sauce.

The large kettle used to steam the soy beans in the first step of the process of making Okamoto’s soy sauce.

The roasted wheat berries before they are cracked to a medium-sized coarseness and mixed with the soy beans.

The moromi mash of soy beans and wheat fermenting in a sea salt brine in a large kioke barrel.

The excess oil from the soy beans and wheat that floats on the surface of the soy sauce after it has been pressed is carefully siphoned off in order to preserve the relative lightness and nuanced flavor of Okamoto’s classic style of soy sauce.

A Family of Soy Sauces

Okamoto’s soy sauce is designed for the region’s food, especially the mild, flaky white fish and delicate seafood available in the Seto Inland Sea, like sea bream, red snapper, flounder, oysters, and squid. It is good for all of the kinds of traditional home-cooking of western Japan, where dishes are lightly seasoned with the salt and umami of soy sauce and not overly flavored by it. Okamoto soy sauce’s mild, nuanced flavor can enrich simple dishes of fresh tofu, blanched vegetables, and lightly fermented pickles and enhance dressings, sauces, stocks, and broths.

Like all artisanal soy sauce brewers, Okamoto makes one soy sauce primarily for cooking and another for finishing foods. Its cooking soy sauce is its regular grade koikuchi soy sauce. Its finishing soy sauce is the koikuchi soy sauce that has been refined by being slowly dripped and only lightly pressed it at the end. This process makes it makes it smoother and lighter. The finishing sauce comes in pasteurized and unpasteurized versions. The unpasteurized type, called “Shima” (which simply means “Island”), is an opportunity to taste Okamoto’s style of soy sauce in its purest form as a surge of flavor on the palate.

From left to right: Okamoto’s koikuchi soy sauce, “Shima” unpasteurized finishing soy sauce, usukuchi soy sauce, and saishikomi soy sauce.

Okamoto’s ponzu sauce is a blend of its koikuchi soy sauce and kabosu citrus.

As the main provider of high quality artisanal soy sauce in its local market, Okamoto makes a range of types of soy sauce to meet the cooking and eating needs of its customers. These include usukuchi soy sauce, a ponzu citrus blend, a rich and creamy, double-brewed, three-year aged saishikomi soy sauce, and a BBQ sauce made in collaboration with one of the island’s most popular restaurants called Kiku-ya. For all of these sauces, Okamoto uses its koikuchi soy sauce as a base and incorporates special local ingredients and innovations. For example, its ponzu is made with kabosu citrus, which is the most traditional type of citrus used in Japanese home cooking. Kabosu is a native Japanese citrus that has a wonderful forest-like fragrance and woody flavor. Okamoto uses kabosu from Oita prefecture on nearby Kyushu Island, which is known for growing the best kabosu in the country.

Okamoto’s usukuchi soy sauce is especially unique. Usukuchi soy sauce is saltier, lighter-colored, and has less intense umami than koikuchi soy sauce, and is used as much, if not more, than koikuchi soy sauce in western Japan because it does not overpower the region’s fresh foods and light cooking. Most brewers make usukuchi by using a greater amount of wheat than soy beans, instead of the standard koikuchi recipe of using equal parts of soy beans and wheat, to lighten the the sauce’s umami and color. Okamoto, however, sticks to the standard proportions and lightens the umami of the soy sauce by boiling the soy beans instead of steaming them and by brewing the soy sauce for only one year instead of two. As a result, Okamoto’s usukuchi soy sauce is a more flavorful, darker colored, home-cooking type of usukuchi.

Here is a list of Okamoto’s soy sauces and their recommended uses:

  • Koikuchi - For making meat marinades and grilling foods and in simmered and braised dishes consisting of a medley of ingredients. It can also be used as a dipping sauce.

  • Dashi-joyu - A versatile, all-purpose pre-mix of dashi and soy sauce commonly used as a base for all kinds of dishes. For marinades, simmered and braised dishes, and salad dressings, Okamoto recommends adding two to three parts water to one part dashi-joyu. If using it to make a light soup stock, such as for udon noodles, add nine to ten parts for every one part dashi-joyu. For a stronger broth, as in a nabe hot pot, use three to four parts water for each part dashi-joyu. It can also be used to make a simple yakiniku barbeque sauce by mixing equal parts grated daikon radish and dashi-joyu.

  • Usukuchi - For lightly marinading and cooking seafood and blanching and making vegetable dishes.

  • Saishikomi - Okamoto recommends using this as a finishing sauce when a richer, stronger, sweeter flavored soy sauce is desired. Use a few drops on tofu, sashimi, pickles, and lightly-cooked vegetable dishes, like oshitashi.

For the ponzu and BBQ sauces, use them as a topping for anything you like.


Story & Photos: Tom Schiller

Okamoto Soy Sauce.

Okamoto Soy Sauce 岡本醤油醸造場
2577 Higashino, Osakikamijima, Toyota District, Hiroshima Prefecture 725-2031

Web: http://okamoto-shoyu.com
Tel: +81 (0846) 65 2041

The shop at the front of the brewery is open daily from 10:00 to 17:00. It offers a full range of Okamoto’s various types of soy sauce and blended sauces. It is the only store in Japan where you can buy its ki-joyu (unpasteurized soy sauce) because this needs to be refrigerated. However, you can order the ki-joyu from Okamoto’s online shop, and it will be shipped directly to you within Japan using cool-takyubin (refrigerated express mail). Members of the Okamoto family are more than happy to give visitors tours of the brewery. They recommend making a reservation for a tour, but if you just drop by, chances are someone will be there to take you around.

Okamoto soy sauce is recognized in Japan as being a premium artisanal soy sauce and can usually be found in the food halls of department stores in the country’s major cities. It is also available at specialty food shops and Hiroshima prefecture’s antenna shop called “Tau’ located in the Ginza in Tokyo.

Okamoto Soy Sauce is located on the edge of the sea, a short walk from Tarumi Port.


Getting There

You need to take a boat to get to Osakikamijima Island. Ferries run from several locations on the main islands of Honshu and Shikoku, enabling you to combine a visit with traveling there. There are also ferries connecting Osakikamijima Island to other islands, if you’re making a tour of the area.

From Honshu:

  • From Takehara city, there are regular large car ferries that go to the two separate ports of Shiromizu and Tarumi on the island. From Tarumi port, you can walk to Okamoto Soy Sauce. From Shiromizu, you will need a car or bicycle. There is also a small 24-person ferry from Takehara to Osakikamijima, which is a delight to take. It stops at Maebaru at the tip of the island very near to Farm Suzuki and also to Kinoe Onsen-Hotel Seifukan, one of the best places to stay on the island.

  • There are also ferries from Akitsu, which is a village located about 20 minutes west of Takehara. Akitsu is the birthplace of Japan’s delicately fragrant and complex, soft-water, ginjo type of sake and also the home of Imada Shuzo Sake Brewery, which makes an excellent range of ginjo sakes under the Fukucho brand.

From Shikoku Island:

  • There are ferries from the major port town of Imabari at the northern tip of Shikoku. The ferries first stop at Ocho port on the neighboring island of Osakishimojima, which is another island well worth visiting. Osakishimojima is known as Japan’s “Citrus Island” because of its extensive citrus orchards. The ancient trading port of Mitarai, located a short walk from Ocho, is one of the country’s best-preserved seaports.

A ferry from the city of Takehara on the mainland Honshu Island traveling to the port of Tarumi on Osakikamijima.


Because Osakikamijima is one of the few large islands in the Seto Inland Sea not connected to the mainland islands of Honshu and Shikoku, it has remained a quiet backwater. The main activities for visitors are cycling, hiking, and experiencing the island’s way of life. On the north side of the island is the large compound of the Mochizuki family, who were active in all phases of the island’s commerce: farming, salt-making, shipping, and shipbuilding. Built in the mid-1800s, the compound is open to the public. It is a beautifully-restored example of country architecture in the late Edo period (1603-1868), and a testament to the island’s historic wealth and economic dynamism.

The massive entrance gate to the Mochizuki family compound.

The garden of the Mochizuki house.

There are a number of small inns and restaurants scattered around the island, which mainly cater to the needs of local residents and offer great home cooked meals made with local ingredients. One of the most popular places at lunchtime is Tokumori Shokudo, which serves a hearty ramen using Okamoto’s soy sauce in its broth. At night locals head to Kiku-ya, a yakiniku barbecue restaurant near Tarumi. Their house yakiniku barbecue sauce is made in collaboration with Okamoto and is available at stores on the island and across Hiroshima prefecture.

There are two specific reasons to make Osakikamijima a destination as a day-trip or overnight stay. One is Farm Suzuki, where some of the best oysters in Japan are being raised by Takashi Suzuki, who moved to the island from Tokyo in 2011 armed with a degree in maritime food culture and a passion for introducing to Japan the French-style of using claires, or endens, to raise oysters. There is a small restaurant alongside the oyster ponds where you can enjoy these oysters as well as large, equally delicious kuruma ebi shrimp pulled directly from the waters and served either raw or prepared in a variety of ways.

Takashi Suzuki at the small restaurant on Farm Suzuki.

Late every spring, after oyster season is over, Takashi drains and cleans the old enden salt-making field in which the oysters are raised to ensure the health and pristine flavor of next year’s batch.

The other attraction is Kinoe Onsen-Hotel Seifukan, which is a hot springs resort perched on a hill at the southeastern end of the island. It serves excellent seafood meals to day trippers and overnight guests and also has a cocktail bar overseen by a highly accomplished mixologist. It is the only inn of its caliber in the area, making it a very useful as well as an enjoyable place to stay if you are touring the many small islands in this part of the Seto Inland Sea.

Kinoe Onsen - Hotel Seifukan

Iwasaki Farm
While you’re on the island, look for Iwasaki Farm’s citrus foods. Aki Iwasaki moved with her family to the island from Kyoto eight years ago, bought an abandoned citrus farm, and revived it, so that it is now a large producer of Hiroshima’s famously fragrant and mild green and yellow lemons and other citrus. In addition to selling fresh citrus, Aki makes a range of citrus jams and jellies and also preserves the fruit’s peel for use in locally-made ice creams, drinks, and other food products, all of which are available at stores on the island and mainland markets in Hiroshima prefecture. Another successful side business she has created is selling bags of her preserved citrus peel to bakers and chefs in Tokyo and other big cities.

Aki Iwasaki among the lemon trees in her orchard.

Meitou's Handmade Koji

Meitou's Handmade Koji

The Torii Family of Sauces

The Torii Family of Sauces