Drain the oil from the canned tuna and prepare the tuna.
Finely chop the onion and green onion.
Heat cooking oil in a pan and sauté the onion and green onion.
Add the tuna, then stir-fry with soy sauce, sugar, and pepper.
Place the stir-fried tuna on top of the rice.
Sprinkle with seaweed flakes and sesame seeds to finish.