In a medium bowl, whisk together NAKANO® Seasoned Rice Vinegar, oil, mustard, salt, and if desired, lemon zest. Dice apple and stir into dressing to prevent browning.
In a large bowl, combine rice, walnuts, currants and onions. Spoon half the apples and dressing over rice; mix well. Stir in remaining apples and dressing. If desired, sprinkle with additional seasoned rice vinegar to taste.