How to Make It
In spice grinder, pulse 1/4 cup of the toasted sesame seeds to a fine powder. Transfer the ground sesame seeds to a medium bowl. Add the mayonnaise, rice vinegar, soy sauce, mirin and lemon juice to the bowl, and whisk until smooth. Season the toasted sesame dressing with salt.
In a large bowl, cover the wakame with 1 inch of cold water. Let stand at room temperature until the wakame is hydrated and tender, about 2 minutes. Drain and, using your hands, squeeze out the excess moisture. Transfer the wakame to a serving bowl and add the kale, cucumber, scallions and celery. Toss with half of the toasted sesame dressing until well coated. Sprinkle the salad with the remaining 1 tablespoon of the toasted sesame seeds. Pass the extra toasted sesame dressing at the table.
Look for Kewpie mayonnaise (which is made with rice vinegar and is very popular in Japan) at Asian markets.