Remove the pits from the umeboshi and finely chop them.

Trim the okra and rub with salt (1/2 tsp, not included in ingredients), then rinse with water.

Peel the nagaimo yam, place it in a plastic bag, and lightly mash it with a rolling pin, leaving some texture.

In a bowl, mix the natto with its included sauce thoroughly.

In another bowl, mix the mentsuyu, water, and sesame oil.

Boil water in a pot, cook the somen according to the package instructions, and add the okra 30 seconds before the somen finishes cooking. Rinse the somen thoroughly with cold water and drain.

Slice the cooked okra into small pieces.