Prepare soup seasoning by mixing with hot water and let it chill in the fridge.
Peel the daikon radish, grate it, and place in a small colander to remove excess water.
Slice tomatoes and shiso.
Boil water in a large pot and cook udon for 2-3 minutes. Once it’s ready, cool with cold water and let it drain.
Put udon and chilled soup in a serving bowl and top it with grated daikon radish, tomato, umeboshi, shiso, and grated ginger. Add some ice to further chill.
Mix in the grated daikon radish into the soup as you slurp this dish up!