In a rice cooker, rinse rice; drain. Add water and let stand for 1 hour.& Stir rice before cooking; cook for 20 minutes and let stand for 10 minutes. Combine sugar, the 2 tablespoons salt, and the rice vinegar. Pour over slightly cooled rice; mix well. In a rectangular glass dish, evenly sprinkle 1/4 cup of the furikake nori. Spread seasoned rice over furikake nori. Combine crab, mayonnaise, and the 1/2 teaspoon salt; spread over rice. Layer cucumber and takuwan over crab mixture. Sprinkle with the remaining 1/4 cup furikake nori. Cover and refrigerate. Cut into squares. Makes 20 servings.