Place the mirin, shoyu, water and sweetener in a small sauce pan. Bring to a boil, reduce flame to low and simmer, while constantly stirring, for 3 minutes. Remove from heat. Place the ginger and garlic in the pan and mix. Cool to room temperature. Place in a glass jar, seal and refrigerate until ready to use. Keep any remaining refrigerated for later use.
Per serving - 17 calories, 0 g fat (0% calories from fat), 1 g protein, 4 g carbohydrate, 0 g fiber, 0 mg cholesterol, 428 mg sodium