Mix until smooth, cornstarch and water in a small bowl, to make a 'slurry'. Set aside.

Combine soy sauce, sake, granulated sugar, Mirin, ketchup, apple juice and pepper in saucepan and cook for 10 minutes over medium heat.

Gradually stir in dissolved cornstarch solution, mix well. Remove from heat and enjoy.

This Teriyaki Sauce may be stored in the refrigerator for up to one week.