For Dressing: Mix all the ingredients together in a mixing bowl. Use for the hijiki salad.
Place the hijiki in a large mixing bowl. Add about 1 1/2 to 2 quarts of warm water over and mix. Let set uncovered for about 30 minutes, to reconstitute the dried seaweed. Once soft, drain in a colander or a sieve, and rinse with water. Drain again thoroughly and place in a mixing bowl for the salad. Add the green onions.
Spiral cut the carrots: Using a spiral slicer, spiral-cut 3 to 4 inch lengths of carrots, enough to make 2 cups. If the spirals are very long then break up the lengths into smaller pieces. If no spiral slicer is available, simply cut the carrots in half and slice thinly on the diagonal. Use 2 cups of sliced carrots for the recipe. Top the vegetables with the Sesame Pineapple Dressing, and toss to coat. Serve cold.