Julienne the daikon and leave it in a bowl of ice water for 5 minutes (this is to make it nice and crisp!), then drain and spin dry in salad spinner (or if you don’t have one, pat it dry with paper towel).While daikon is soaking, cut the mizuna into 4-5 cm lengths, and chiffonade the shiso.
Combine the daikon, mizuna and shiso in a bowl and mix.
Remove the pits from the umeboshi, then mince and combine with the other dressing ingredients.
Dress the salad just before you’re ready to eat it!