In a bowl, whisk together the low-sodium soy sauce, water, mirin, brown sugar, and rice wine vinegar; whisk until the brown sugar is completely dissolved; set aside.
Place the chicken pieces in a separate bowl and add the vegetable oil, ground black pepper, garlic, ginger and dried ginger powder; toss together until ingredients are well mixed through.
Pour in ¼ cup of the prepared sauce mixture; this will create the marinade.
Stir into the chicken until everything is well combined; marinate for 10 minutes.
Place a frying pan over medium heat.
Once the pan is hot, transfer the marinated chicken to it and spread out to cover the surface of the pan.
Cook the chicken for 7 minutes, turning a few times, until the chicken is cooked through and lightly browned.
Whisk together the cornstarch with one tablespoon of water until smooth.
Pour the mixture into the remaining sauce mixture and whisk to combine.
Pour the sauce into the frying pan and stir through the fried chicken.
Continue to cook for 2 minutes until the sauce has thickened and adhered to the chicken.
Remove from the heat, plate, and garnish with the toasted sesame seeds.