Rinse and dry the mizuna (dirt tends to hide near the stems). Cut off and discard the bottom stems of the mizuna. Chop the mizuna into 2-inch pieces.
Add mizuna to a salad bowl and place cucumbers, tomatoes, and tofu on top. Drizzle sesame dressing over (you may not need all of it).Tip: Silken tofu is very delicate and will break when you toss the salad. For nice presentation, you can serve the salad untossed with dressing on the side or dressing drizzled on top but not tossed. Or, you can toss together all the ingredients except tofu, then add the tofu on top.