Prepare the rice: Break apart any large clumps of chilled cooked rice and set it aside.
Cook the kimchi: Heat the cooking oil in a wide skillet over medium-high heat. Add chopped kimchi and stir-fry for about 2 minutes until softened and fragrant.
Add the rice: Add the cooked rice and toss with the kimchi until the ingredients are evenly combined.
Season the rice: Add kimchi juice and gochujang, then stir until the seasoning coats the rice evenly.
Fry the rice: Spread the rice across the skillet and let it cook briefly without stirring so some grains can develop lightly toasted edges.
Toss and continue: Stir the rice, spread it out again, and cook for another short period until hot and lightly toasted.
Add sesame oil: Turn off the heat and mix in the toasted sesame oil and chopped green onions.
Garnish: Sprinkle with toasted sesame seeds and roasted seaweed.
Serve: Transfer the kimchi fried rice recipe to serving plates and top with a fried egg if desired.