Drain the oil from the canned tuna using a sieve.

Slice 1/2 onion thinly.

Mix soy sauce, mirin, and corn syrup in a pan and bring to a boil.

Add the sliced onion to the pan and stir-fry until softened.

Heat oil in a pan and add 2 eggs directly without whisking.

Scramble the eggs lightly with chopsticks, adding a pinch of salt.

Place cooked rice on a plate and layer the scrambled eggs on top.

Add the stir-fried onions on top of the eggs, pouring the soy sauce mixture over them.

Top with the drained tuna.

Drizzle mayonnaise over the dish and sprinkle sesame seeds and optional parsley.