This is eaten along the Kashima-nada coast, running from Kashima in Ibaraki down as far as Choshi in Chiba. The seaweed used is kotoji tsunomata or tsunomata, which grows to about twenty centimeters on rocks in the intertidal zone, where it is uncovered twice a day.

Heated in a pan, it thickens. Cooled again, it sets solid. That property was known and put to use long before anyone thought of the seaweed as food at all: it went into soap, and it went into glue.

The connection between this seaweed and New Year is a commercial one. Merchants from Choshi would come round at the end of the year selling kotoji tsunomata for the holiday, and households along this coast started making a set jelly from it as part of the New Year spread.

Cut into pieces, the slices are translucent with the fibers of the seaweed suspended visibly inside them, like something in a museum case. It gets eaten with soy sauce and whatever condiments happen to be around, and its role among the heavily seasoned dishes on an osechi tray is to be the one clean thing that you keep going back to between the others. A seaweed that was once used as adhesive now sits on a lacquer plate on the first of January.