In 11x7-inch glass or plastic container, arrange shrimp in single layer. In 1-quart saucepan, heat soy sauce to boiling over high heat. Stir in gingerroot; reduce heat to medium. Simmer uncovered about 5 minutes or until liquid is reduced by half. Stir in vinegar, sugar, sake and salt; pour over shrimp. Cover; refrigerate 2 to 3 hours.