1. In a medium-sized pan over medium heat, add the dashi (instructions below), soy sauce, mirin, and sugar.
2. Add the sliced onions and diced chicken pieces. Cook until the chicken is cooked all the way through, about 6-8 minutes. Flip the chicken halfway through.
3. Reduce the heat to low. Pour a little more than 1/2 of the beaten eggs evenly over the chicken and onions, away from the edges of the pan. Cover the pan with a lid and let it cook for about 1-2 minutes, or until the eggs are just set but still slightly runny.
4. Divide the cooked rice between two bowls. Carefully spoon the chicken, onions, and egg mixture over the rice. Garnish with green onions.

Dashi Instructions:

1. Place the kombu in a pot with the water and let it soak for about 30 minutes.
2. After soaking, heat the water over medium heat. Just before it begins to boil, remove the kombu from the pot.
3. Once the kombu is removed, bring the water to a boil, then add the katsuobushi. Let it simmer for about 5 minutes.
4. Turn off the heat and strain the broth through a fine mesh sieve or cheesecloth to remove the bonito flakes. Use immediately or store in the fridge for up to a few days.