Cut the chicken breast into bite-sized pieces.
Slice the onion and green onion thinly.
Add some cooking oil to a pan and sauté the onion.
Add the chicken breast and stir-fry until cooked through.
Add soy sauce, mirin, sugar, and water and bring to a boil.
Beat the eggs and pour them around the pan to cook.
Place all the ingredients on top of rice and garnish with green onion.