Combine teriyaki sauce, brown sugar, garlic, and black pepper. Mix well.
Add chicken and water chestnuts and mix well. Cover and let marinate 2-4 hours in refrigerator.
Soak toothpicks in water to avoid burning.
Preheat broiler.
Place chicken liver on top of each half water chestnut, then wrap in bacon pieces. Secure with toothpicks.
Place rumaki in oven, about 2 inches away from broiler.
Cook 3-4 min, then turn and cook an additional 2-3 min, until bacon is browned.
Serve immediately.