Place the water, beans and kombu in a 4-quart pot. Bring to a boil,reduce heat and cook, covered, for 1 1/2 hours. (you can also pressure-cook beans for 1 hour in 2 1/2 cups water). Remove the kombu. Drain the beans, reserving the cooking water.
Puree the beans in a food processor or mash to a thick paste in a bowl or mortar. Add some of the reserved cooking water to get a dip consistency.
Add the oil, cayenne, ginger and umeboshi paste to the beans and mix well. Add the salt and serve.