Make the sauce: In a saucepan over medium-high heat, combine soy sauce, white vinegar, brown sugar, ground ginger, and onion powder. Stir until the sugar dissolves and the mixture comes to a simmer, about 5 minutes.
Mix cornstarch slurry: In a small bowl, whisk the cornstarch with the cold water until smooth.
Thicken the sauce: Pour the cornstarch slurry into the simmering sauce, stir, and bring to a boil. Reduce heat and boil gently, stirring occasionally, for 7–10 minutes until the sauce thickens. Remove from heat and let cool; refrigerate if making ahead.
Heat oil: Fill a heavy pot or deep fryer with enough vegetable oil to deep-fry the wings and heat to medium-high (about 350–375°F / 175–190°C).
Prepare wings: Pat the chicken wing sections dry with paper towels. Place the flour in a shallow bowl or plate and dredge each wing, shaking off excess flour.
Fry wings: Fry the dredged wings in batches for about 5–7 minutes, until golden brown and cooked through. Transfer fried wings to paper towels to drain.
Toss in sauce: Warm the prepared teriyaki sauce in a large frying pan over medium heat. Add the fried wings and toss until evenly coated.
Serve: Transfer wings to a serving platter and sprinkle with sesame seeds before serving.
