Narezushi: The Fermented Ancestor of Modern Sushi

Long before vinegar, sushi meant fish packed in rice and left to ferment, and a few regions still make it the old way.

Published October 18, 2026 at 7:44 PM JST | By Tokyo Paul

Quick answer: Narezushi is the oldest form of sushi: fish preserved with salt and fermented with rice for months, after which the sour fish is eaten and the rice is traditionally discarded. Funazushi, made from carp near Lake Biwa in Shiga Prefecture, is its best-known surviving example, with a strong aroma and tang.

What narezushi is

Narezushi means aged or matured sushi. The method uses salted fish packed with cooked rice in a container, then weighted and left for a long period so that lactic fermentation takes place. The rice sours, the fish becomes acidic and soft, and the whole thing keeps far longer than fresh fish. In the early form, the fermented rice was thrown away and only the fish was eaten.

That is quite different from the sushi most travelers know. Modern sushi uses vinegar to season rice, giving the tang quickly. Narezushi gets its sourness from slow natural fermentation. The flavor is strong, sharp and complex, sometimes compared to aged cheese or fermented foods in other cultures. It is an acquired taste, valued as a link to the origins of sushi itself.

Where sushi began

Food historians generally explain that fermenting fish with rice to preserve it was a technique found in parts of Southeast Asia and southern China, and that it reached Japan in ancient times. Over centuries, people in Japan shortened the fermentation, started eating the rice too, and eventually added vinegar to imitate the sourness without waiting. That process led to oshizushi, then to hand-formed nigiri in Edo.

Because the story spans many centuries, the details are debated, and scholars hold varying views. What is widely agreed is that narezushi represents an early stage in the development of sushi, and that it survives in a few regions where the tradition was never abandoned. Seeing it today is a chance to glimpse an older Japanese food culture.

Funazushi and Lake Biwa

The most famous narezushi is funazushi from Shiga Prefecture, around Lake Biwa, Japan's largest lake. It is traditionally made from nigorobuna, a native crucian carp species, which is salted for months, then packed with rice and fermented for a long period, often a year or more. The tradition goes back many generations in the lakeside communities.

Funazushi has a powerful smell and a taste that combines sourness, saltiness and a deep umami note. It is often sliced thin and served in small amounts. Some people eat it with the fermented rice, which has become soft and tangy, and some eat it as a snack with sake. Because nigorobuna populations have faced pressures, the fish is valued and the product is often expensive.

Other regional narezushi

Funazushi is not alone. Along the coast and in mountain areas, other fermented sushi forms exist. In Wakayama and Mie, saba narezushi uses mackerel. In Tohoku, there is iizushi, in which fish is fermented with rice, vegetables and koji. In Akita, hatahata-zushi uses sandfish. In Ishikawa, kabura-zushi pairs yellowtail with turnip and koji, a winter specialty.

Each of these dishes has its own character. Some are milder, with the ferment shorter and the rice tender. Others are intense. They reflect local ingredients and climates, and the use of koji, a mold used in sake and miso, brings sweetness. If you are curious, look for them in regional food halls and local restaurants during their season, usually winter.

How to try it as a first-timer

If you want to taste narezushi, start with a small portion. Specialty restaurants in Shiga near Lake Biwa, as well as some shops in Kyoto and Osaka, serve funazushi in thin slices or as part of a tasting menu. It also appears as a delicacy at fine dining counters. Ask the staff how to eat it; some places serve it with hot water poured over it, as a soup, which mellows the aroma.

Another approach is to choose a milder regional version such as kabura-zushi, which has a sweet, tangy flavor and a pleasant texture, closer to a pickle. Do not be discouraged if the first bite is intense. Taking tiny bites with a sip of sake or tea helps. As always, check shop sites for availability, because quantities can be limited.

It also helps to know that tastes differ between producers. Some funazushi is aged longer and has a deeper, sharper flavor, while a milder batch might taste closer to a soft pickled fish with a gentle tang. If a shop offers a small sample, taking it is a sensible way to decide before buying a larger portion. Locals often describe the aroma first, and the taste follows more gently.

Food safety and the right setting

Fermented foods require careful processing. Narezushi should be bought from reputable shops or served in established restaurants, where producers follow traditional methods and regulations. Do not try to make it at home without proper guidance, as improper fermentation can be unsafe.

When purchasing as a gift, check storage instructions and the best-before date. Many products need refrigeration. If you have health concerns, are pregnant or have a weakened immune system, ask your doctor whether fermented fish products are appropriate. The food is intended for adults who appreciate strong flavors. It is traditionally consumed in small amounts, as a delicacy rather than a main course.

Many curious travelers first meet fermented sushi in a museum or cultural exhibit, where displays show the old method of packing fish in wooden barrels with rice. Seeing the process makes the flavor easier to understand. If you are near Lake Biwa, local museums and heritage centers sometimes explain the fish, the lake and the craft in detail, and some shops offer small tasting portions for visitors.

Pairings and etiquette

Narezushi goes well with sake, especially a dry, crisp type, or with hot tea. Because of its intensity, it is usually eaten alongside plain rice, pickles and mild vegetables. In a restaurant, the dish may arrive as a small appetizer or a course in a kaiseki meal.

Etiquette is simple: eat slowly, in small bites, and appreciate the effort behind it. It is acceptable to say if you find it too strong. Do not waste it if you cannot finish; sharing with a companion is a polite alternative. Many Japanese people also find funazushi strong, so you will not be alone in your reaction. Curiosity and respect for tradition are what matter most.

A small cup of sake and a few slices of narezushi make a classic pairing, but tea and plain rice also work well. Some restaurants pour hot tea over a small portion of funazushi and rice, turning it into a gentle, savory soup that softens the aroma. If you are not sure how to eat a particular product, ask the shop staff; they usually appreciate the interest and are glad to explain.

Frequently Asked Questions

Is narezushi the same as regular sushi?

No. It is the ancestor of modern sushi, made by fermenting fish with rice for months. Regular sushi uses vinegared rice and is eaten fresh. Narezushi has a sour, strong, cheese-like flavor.

What is funazushi?

Funazushi is a narezushi from Shiga Prefecture made from nigorobuna carp from Lake Biwa. The fish is salted and fermented with rice for a long time, giving a strong aroma and tangy flavor.

Do you eat the rice?

In the earliest tradition the rice was discarded. In funazushi today, the fermented rice is often eaten with the fish or used in soup, and it has a tangy, soft texture.

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More guides from Tokyo Paul: Hatahata: Akita's Winter Sandfish, Kakinoha-Zushi: Nara's Persimmon Leaf Sushi and Shio Koji: Salted Rice Malt in Japanese Home Cooking.