Cut spam into cubes and slice onion thinly. Beat the eggs and set aside.

Pan-fry the spam cubes until golden brown.

In a pan, combine onion, soy sauce, mirin, sugar, and black pepper. Simmer until the sauce thickens.

Prepare scrambled eggs by cooking beaten eggs in a lightly oiled pan over low heat, stirring gently.

Assemble the dish by layering rice, scrambled eggs, thickened onion sauce, and fried spam cubes in a bowl.