Arrange the bacon on a rack over a sheet pan and bake at 400°F for 8 minutes until some fat renders but the strips remain flexible.
Stir the soy sauce, brown sugar, ginger and garlic powder together and marinate the chicken livers for 15 minutes in the refrigerator.
Place one liver piece and one water chestnut half on each bacon strip, roll tightly and secure with a soaked toothpick.
Return the rumaki to the rack and bake for 12 to 14 minutes until the bacon is browned and the liver reaches 165°F.
Rest for 5 minutes and remove the toothpicks only if the rolls hold securely.