Tsugani is the mitten crab. It lives in the Shimanto, the Niyodo, and the Monobe rivers. They run from about ten centimeters across up to nearly thirty in the largest ones, which is a substantial animal for a river.

The season is judged by the plants rather than by a date. When the itadori and the kudzu come into flower, in autumn, the crabs begin moving downriver to spawn, and the fishing starts along the banks. The permitted season runs from the first of August to the thirtieth of November.

The method is not gentle. The carapace and the apron are removed, and the crab, still alive, goes into a stone mill and is ground to pieces.

That mash is put into a colander and strained inside a pot of boiling water, so that everything the shell was holding goes out into the broth and stays there. Nothing is picked out and eaten as meat; the whole animal becomes liquid. The same crab is used for tsugani somen, where this broth is served with noodles in it, and for tsugani meshi, in which the animal is cooked into the rice with its shell still on. Because the shell is never separated out and thrown away, what ends up in the bowl is very much stronger than a crab broth usually is.