Finely chop the onion and green onion.
Cut the kimchi into bite-sized pieces.
Add cooking oil to a pan and sauté the green onion to make scallion oil.
Add the onion and kimchi and stir-fry.
Drain the oil from the tuna, add it, and stir-fry together.
Add the rice and stir-fry everything evenly.
Season with soy sauce and pepper.
Serve in a bowl to finish.