The Kiso, the Nagara, and the Ibi. Three rivers crossing the Nobi plain on their way to the sea, and in the low country where they meet, carp, crucian carp, and mullet were plentiful.

Sea fish did not reach inland easily, so this is where the protein came from. The dish is eaten in Owari, in the southwest of Mino in Gifu, and over in Kisosaki in Mie, which is to say it follows the water rather than any prefectural line.

The miso matters more than the fish does. This is mame-miso, red miso, made by growing koji directly on soybeans and then aging the result for a year, sometimes two or three. What that produces is deep savoriness with an astringency behind it, and that astringency is precisely what handles the smell of river fish while leaving the flavor standing.

The method takes a day. Soybeans soak overnight. They go into the pot first and the fish is laid on top of them, and the whole thing sits over a low flame for around five hours before the miso is added and the simmering continues. The cold-water crucian carp of late December and January carry the most fat. It used to be left sitting on a shichirin, which is another way of saying nobody watched it.