Igo is a small seaweed that grows attached to larger ones, kelp and sargassum. On Sado they call it igo, on the Niigata mainland ego, and the difference in the vowel marks the strait between them.

Dried in the sun, then simmered with the water carefully judged and worked until it dissolves, it is spread thin and left to set. That is the whole process. It comes out as a pale sheet, sliced into strips and eaten with ginger and soy sauce or with vinegared miso. The texture is dense and slightly chewy, the flavor mild, with a faint smell of the shore.

What interests me is the route it took. The practice is said to have come from the okyuto culture of Kyushu, carried by the kitamaebune coastal trading ships from Hakata up to Wajima on the Noto peninsula, across to Sado, and from there into Echigo.

So the shape of an old shipping route is preserved inside a dish. Somebody on a boat carried a technique north in stages, and it took hold at each landing along the way. It used to be food for weddings and funerals, the formal occasions when a household put on a spread. Now it is eaten all year round as an ordinary thing, which is usually the direction these long journeys end up going in.