In a medium bowl, mix together teriyaki sauce, brown sugar, garlic, and ginger root. Place chicken livers and water chestnuts in the mixture. Marinate in the refrigerator for at least 2 hours, overnight is best.
Place 24 toothpicks into water to soak while waiting for the marinade. (extra if you are prone to breaking them like I am!)
Remove the livers and water chestnuts from the marinade and discard the marinade.
Preheat your oven to 375°F. Line a baking sheet with aluminum foil, then place an oven-safe baking rack on top.
Lay 1 bacon half on a cutting board and place 1 piece of liver and 1 water chestnut in the center. Wrap each half slice of bacon around one chicken liver half and one water chestnut. Secure by skewering with small skewers or toothpicks.
Repeat with the remaining ingredients to make 24 rumaki. Place on the wire baking rack.
Bake the rumaki for 20 minutes, then flip on their sides and continue to bake until the bacon is cooked.
Remove and place onto a serving platter and serve immediately.
Notes
I find that the teriyaki is too bitter by itself when used with liver, so I add brown sugar for sweetness.