More than five hundred years ago, the lord who governed the Suko area of what is now Shiroishi is said to have taken particular care of the farmers under him, and to have put effort into improving the rice grown there. The rice became known well beyond the district, valued for sushi and for brewing.

The people, according to the account, made a sushi from what the sea and the mountains gave them and presented it to him in thanks. That is the origin story, and whatever its accuracy, it is unusual for running in that direction: gratitude going up rather than tribute being demanded.

It is built in a morobuta, a shallow wooden box. Seasoned rice is packed in and divided into sections, and each section is heaped with something: grilled mudskipper, shredded omelet, shiitake and burdock and carrot simmered sweet and salty. The vinegar for the rice is made by steeping grilled mudskipper bones in it, so the fish is present twice, in the topping and in the grain.

Mudskipper is hard to get now, and shrimp or gizzard shad often stands in. It was made for festivals, for people who had come to pray at the local temple, and for the day a married daughter came back to the house she grew up in.