Hokki, properly ubagai, is a large clam. It comes ashore along the Miyagi coast from winter into spring, and the port at Isohama in Yamamoto has been landing a great deal of it for a long time. The fishery cooperative sets a minimum size: nothing under nine and a half centimeters comes out of the water.

The method is a two-stage one. The raw clams are briefly cooked in a soy-based liquid, and then the rice is cooked in that liquid, so the grain takes everything the clam gave up. But the clams themselves are removed first, because a hokki that sits through a rice cooking cycle turns to rubber. They go back in afterward, folded through the finished rice.

The season runs roughly from December through to May. In March and April the clams are carrying roe and building reserves, and the flavor deepens noticeably in those weeks.

In Yamamoto and Watari this sits alongside harakomeshi, the autumn salmon and roe rice, as one of the two dishes that mark the year. It began as home cooking and has moved outward from there: restaurants in the town now list it on the menu, which is the usual trajectory for such a dish, and the households making it at home have not stopped doing so.