Kagawa does not get much rain, so its agriculture has always depended on reservoir ponds instead of rivers. There are more than ten thousand of them across the prefecture, and crucian carp live in a great many of them.

When the busy farming season comes to an end, in autumn and on into winter, the ponds are drained down. At that point the carp are approaching spawning: the fat is on them, the flesh has firmed, and the muddy quality that freshwater fish carry has mostly gone. They were called kanbuna, the cold-season carp, and they were waited for.

In the mountain and farming villages here, a long way from the sea, that was a valuable source of protein, and it arrived once a year as a byproduct of maintaining the water supply.

The fish is filleted, sliced thin, cured first in salt and then in vinegar, and dressed together with daikon in a vinegared miso made using Sanuki white miso. One account of the name says that carp were once called teppo, guns, and that teppo-ae wore down over time into teppai. Nobody is certain. The dish exists because somebody had to empty a pond every autumn, and everything else about it followed on from that single fact.