How to Make It
In a medium saucepan, combine the kombu with 8 cups of water and bring to a simmer. Stir in the instant dashi and remove the pan from the heat; let stand for 30 minutes. Strain the broth through a fine-mesh sieve set over a large bowl; discard the solids or reserve for another use. Return the broth to the saucepan, season with salt and bring to a simmer. Add the noodles and cook until al dente. Divide the noodles and broth among 4 bowls.
Meanwhile, in a medium saucepan of simmering water, break each egg into a small bowl and gently pour into the simmering water. Cook until the whites are just firm and the yolks are still runny, 2 to 3 minutes. Using a slotted spoon, transfer the eggs to a paper towel–lined plate and let drain briefly. Top each bowl of noodles with an egg. Spoon a tablespoon of daikon next to each egg, then garnish with nori. Serve with the remaining daikon on the side.