In the Edo period the kitamaebune ships brought kelp down from Hokkaido, and Toyama put it together with the fish coming out of its own bay. That combination is where this begins.

There was no refrigeration anywhere in this. Kelp draws water out of whatever it is pressed against, and drawing water out of raw fish buys a day or two, so this was a preservation method long before it was anything else. That is worth holding onto.

But something happened along the way. The kelp does not only remove moisture, it gives up its own flavor into the fish, and the flesh firms and matures and acquires a particular springiness that it did not have when it was cut. What began as a way of not losing the fish became the reason for eating it that way.

The fish used is usually kajiki, which people here call sasu, though sea bream and flounder go into it as well. The slices go between sheets of kelp, get covered and weighted lightly, and are left overnight. Households in Toyama city buy more than twice the national average quantity of kelp. This turns up at celebrations, and it also turns up on an ordinary Tuesday evening alongside a glass of something cold.