All over the Aizu region

Migaki nishin, leaves of sansho (Japanese pepper)

In the Edo period (1603-1868), when there was almost no distribution of raw fish in Fukushima, nishin caught in Hokkaido were dried and made into "migaki nishin" for distribution outside of Hokkaido. This fish was then transported to the Aizu region, where it came to be valued because it could be preserved and was a source of protein. In Fukushima, in particular, winters are long and crops are scarce for a long period of time, so food that could be stored for a long time was favored. Migaki nishin became a familiar foodstuff, and local dishes such as "vinegared nishin" came to be prepared.
Nishin no sansho zuke" (Nishin marinated in Japanese pepper) is another dish using migaki nishin, which is made by covering it with sansho leaves and seasoning it with soy sauce, vinegar, and sake. It is commonly eaten in the Aizu-Wakamatsu area, and is so familiar that there is a special bowl called a "nishin-bachi" for sansho pickles. The rectangular bowl is said to be made of Aizu Hongo-yaki pottery and matches the size of the migaki nishin.

It is most commonly eaten from spring to early summer, when sansho (Japanese pepper) is harvested. There are two types of migaki nishin: hard "hon-koshi" and slightly softer "han-koshi," but in the past, hon-koshi was often used because of its high preservability and concentrated umami flavor. Because migakinishin has an odor, the purpose of this dish was to remove the odor and enrich the flavor by adding fresh sansho (Japanese pepper).

Place sansho leaves in a Nishin bowl, wash the Nishin thoroughly with a scrubbing brush, and arrange the Nishin with their heads removed in a tight line. Then the leaves are covered with vinegar, sake, and soy sauce, and the bowl is covered with a lid and weighted down with a weighted stone. After a few days to a week, the flavors will soak in well. For a delicious taste, you should also rehydrate the nigashin in the water in which rice is washed.

Nishin bowls for making sansho-zuke (Nishin-nishin) are still sold in Fukushima Prefecture, and the culture and dietary traditions continue to be passed down.