Heat 2 tablespoons of the vegetable oil in a medium skillet over medium-high heat. Add the cubed chicken, onion powder, garlic powder, red pepper flakes, and brown sugar. Stir thoroughly to coat the chicken with the seasonings.

Cook the chicken for approximately 10 minutes, stirring as needed, until it is fully cooked and evenly browned. Transfer the chicken from the skillet and set it aside.

Pour the remaining 1 tablespoon of vegetable oil into the same skillet. Add the cooked rice and separate any compacted pieces with a spoon or spatula.

Move the rice outward to form an open space in the center of the skillet. Crack the eggs into the opening and immediately scramble them. Continue cooking and stirring the eggs until they are completely set.

Combine the scrambled eggs with the rice. Pour in the Japanese barbecue sauce and stir until the rice is uniformly coated.

Return the cooked chicken to the skillet and stir until it is heated through. Sprinkle the dish with sesame seeds and, when desired, finish with chopped scallions before serving.