"Kyushu shoyu: why it is sweet, how it differs by prefecture, and which bottle to start with"

People eating sashimi in Kyushu for the first time are usually startled by the shoyu. Thick, almost syrupy, and unmistakably sweet. To a palate used to the shoyu of the Kanto region, it can feel like a different condiment altogether.

That sweetness is no accident. It is a food culture the history and climate of Kyushu spent several hundred years building.

The sweetness traces back to the "Sugar Road"

In the Edo period, sugar entered the country at Dejima in Nagasaki and travelled along the Nagasaki Kaido, the highway running up to Kokura, on its way to the rest of Japan. The route later came to be called the "Sugar Road."

In northern Kyushu, which sat along that road, sugar was comparatively easy to obtain even though it should have been a luxury, and cooking with it became a symbol of prosperity and of welcome. It is the same reason Kyushu has so many famous sugar confections, from castella to marubouro.

The sweetness of the shoyu is an extension of that sugar culture. Food you set before a guest should be sweet. A flavor you send to someone who matters should be sweet. The sweet shoyu of Kyushu has that memory of welcome dissolved into it.

Climate and fish chose the sweetness

The other reason is the climate of Kyushu and what it puts on the table.

In the warm south much of the work brought on a sweat, and the body wants sugar and salt at the same time. And the oily fish caught in nearby waters - bonito, yellowtail, mackerel - go better with a thick, sweet shoyu that can carry the fat than with a sharp, dry one.

The reason "sweet shoyu for sashimi" is taken for granted in Kagoshima is not theory. It is the answer that daily meals kept testing and kept confirming.

Even within Kyushu, the sweetness differs by prefecture

"Kyushu shoyu is sweet" gets said as though the region were one thing, but in practice each prefecture sits somewhere different. It helps to remember that broadly, the further south you go, the sweeter it gets.

People trying Kyushu shoyu for the first time sometimes find the intense sweetness of Kagoshima simply too much. If you are used to Kanto koikuchi, start around Fukuoka or Saga and work south once your palate has adjusted - it is an easier route in.

If what you want is the sweetness Kyushu is known for, though, go straight to Kagoshima.

How to choose sweet shoyu: what to look for on the label

There are three things to check, in a shop or online.

1. The words for "sweet" on the label Not every shoyu from Kyushu is sweet. The same brewery often makes both a dry and a sweet version. Check what the label says.

2. Sugars in the ingredient list The sweetness of these bottles comes from sugar, high-fructose corn syrup, stevia and the like. It is fair to assume that the higher the sugars sit in the ingredient list, the sweeter the bottle.

3. Whether it is thick Anything labelled as thick or as a sashimi shoyu has been built for viscosity as well as sweetness. Choose that type if you want it to cling to sashimi; choose a standard sweet bottle if you also want an all-purpose shoyu for simmering.

Note that sweetness sits on a different axis from the JAS categories such as koikuchi and usukuchi. Most sweet shoyu is classified as koikuchi and then sweetened. Classified as koikuchi, but sweet to taste - that is the part people find confusing.

One caution in use: cut the sugar

If you are using sweet shoyu in place of your usual bottle, do not leave the sugar and mirin in the recipe as written.

Because of those sugars, it also scorches more easily. For teriyaki and stir-fries, lower the heat from your usual setting or add the shoyu at the finish and nothing will go wrong.

"Kanro": the household flavor of Kagoshima

The standard bearer for the sweet shoyu of Kyushu is "Sakurakaneyo Kanro," from Yoshimura Jozo in Ichikikushikino, Kagoshima Prefecture.

Founded in 1927, the maker has kept this intensely sweet koikuchi shoyu in Kagoshima kitchens ever since. It is built on kiage (raw, unpasteurized shoyu) aged for over a year, with a syrupy sweetness layered on top. Locally, this one bottle goes on sashimi, into simmered dishes, and over rice with raw egg as a matter of course.

For anyone from outside the prefecture, the culture shock of sweet shoyu is itself part of travelling in Kyushu. A flavor you could once only meet on the road, now on your own table.

Sweet shoyu is not only a Kyushu thing

It surprises people, but the range of sweet shoyu reaches beyond Kyushu. It is used from the San'in coast through the Seto Inland Sea and into Shikoku.

• Shimane and Tottori: there is a culture of pairing a sweeter shoyu with Izumo soba and with sashimi
• Hiroshima: sweet bottles matched to the fish of the Seto Inland Sea have taken hold
• Kagawa and Ehime: as with the white miso culture of Sanuki, there is a leaning toward sweetness

What these places share is a warm climate and a sea that yields oily fish. The same conditions that produced the sweet shoyu of Kyushu. Sweet shoyu is not a Kyushu monopoly; it is a food culture found across much of western Japan.

Even so, Kagoshima stands well out in front on sheer sweetness, so the impression that sweet shoyu means Kyushu is not wrong.

Ways to enjoy sweet shoyu

• Sashimi: start with oily fish such as bonito or yellowtail. The sweetness wraps around the richness of the fat
• Teriyaki and braised pork belly: the seasoning settles without sugar, and the gloss and depth both rise a notch
• Rice with raw egg: the single easiest way to see what sweet shoyu can do
• Mochi and dango: use it straight, in place of sugar and shoyu. This is the taste of a Kyushu childhood snack

Put one bottle on your table to begin with. The food culture of Kyushu will quietly work its way into your everyday cooking.

Frequently asked questions

Why is the shoyu of Kyushu sweet?

Several explanations are offered. Sugar arrived through Dejima in Nagasaki and travelled inland along what came to be called the "Sugar Road," so sugar was close at hand; the warm climate favored sweetness; and sweet shoyu suits sashimi cut from very fresh fish. In Kyushu, sweetness also stood for hospitality.

Which prefecture in Kyushu has the sweetest shoyu?

Kagoshima is generally held to be the sweetest, followed by Miyazaki and Kumamoto. Fukuoka and Saga are lighter by Kyushu standards, and some of their bottles come close to the koikuchi of the Kanto region. Within Kyushu, the sweetness is said to build as you go south.

What dishes does sweet shoyu suit?

Oily sashimi such as bonito and yellowtail is the classic pairing. It also suits chicken teriyaki, braised pork belly, and rice with raw egg. Because you can cut back on sugar and mirin, it settles the seasoning of a simmered dish in one move.

If I am buying my first bottle, which sweet shoyu should I choose?

"Sakurakaneyo Kanro" from Kagoshima is the standard bearer. It is an intensely sweet koikuchi shoyu made by Yoshimura Jozo, founded in 1927, and a fixture in Kagoshima kitchens. It is available on Amazon and makes a good entry point into the sweet shoyu of Kyushu. If you would rather start with something less sweet, a bottle from Fukuoka or Saga is another way in.

Can sweet shoyu replace ordinary shoyu?

It can, but reduce the sugar and mirin. Sweet shoyu has sugars added to it, so following a recipe's sugar as written will leave the dish too sweet. For a simmered dish, halve the sugar or drop it entirely, then taste and adjust. It also scorches more easily, so keep the heat lower for teriyaki.