Taro and fried tofu are simmered together in a stock made from dried sardines. Mushrooms, warabi, and tofu go into the pot after them, and miso is stirred through at the end.

Then the natto goes in, and this is the part that takes attention. It is ground in a suribachi until it becomes a paste, thinned gradually with ladlefuls of the hot soup, and then returned to the pot. Scallion and mustard greens go on top of the finished bowl.

What the ground natto does is give the soup a particular depth and a rounded, softened quality that miso alone does not produce. It also makes it thick, and thickness holds heat. On a snowy morning in Akita that is not a refinement, it is the point.

The origin story for natto itself is attached to the Later Three-Year War in the eleventh century. Farmers, so the account goes, brought boiled beans wrapped in straw to Minamoto no Yoshiie's forces, who were short of supplies. After some days the beans had changed color and were pulling threads, and somebody tried them anyway and found them good. In the southern inland part of the prefecture, this soup is what stands where zoni stands elsewhere: made once and reheated across the first three days of the year.