Prepare the sauce by mixing soy sauce, sugar, mirin, and water in a bowl. Adjust the taste to your preference.

Slice the onion, chop the green onion, and green chili.

Pour the sauce into a frying pan and add the sliced onion. Cook over medium heat until the onion softens.

Beat the eggs lightly in a bowl.

Once the sauce and onion mixture starts to boil, slowly pour the beaten eggs into the pan.

Before the eggs are fully cooked, add the chopped green onion and chili on top. Turn off the heat while the eggs are slightly undercooked.