Kyoto sits in a basin. Fresh sea fish was scarce here, and what arrived came over the mountains from Wakasa, on the Sea of Japan side, carried on foot from Obama to Demachiyanagi. The route picked up a name: the mackerel road.

Because walking was the only option, the fish was salted before it left. By the time it reached the city the salt had worked its way properly into the flesh, and the sushi was devised to make use of exactly that condition rather than to disguise it.

Mackerel cured with salt and vinegar is laid along a bar of seasoned rice, wrapped in kombu, and packed in bamboo sheath. With no way to keep anything cold, the care went into small things: the freshness of the salted fish, the boning, the judgment of how much vinegar, keeping a certain dampness in the bamboo.

On festival days households made their own versions and traded them with each other, which is a good indication of how ordinary it was to have one in the house. What has changed is the far end of the road. Almost no mackerel is caught at Obama now, and much of what shops use comes from elsewhere. The road is still there, walked now by people rather than by carriers. The fish it was built for is not.