Start by rinsing the rice under cold water until the water runs clear. Drain well.

In the rice cooker, combine the rinsed rice and water. Add the sliced onion and chicken pieces on top.

In a small bowl, mix the soy sauce, mirin, sugar, and salt. Pour this mixture over the chicken and rice.

Close the rice cooker lid and set it to the regular cooking cycle. Allow it to cook until the rice cooker switches to the 'keep warm' setting.

Once cooked, gently stir the rice and chicken mixture. Drizzle the beaten eggs over the top. Close the lid again and let it sit for 5-10 minutes to allow the eggs to cook through from the residual heat.

Fluff the Oyakodon with a fork, garnish with chopped green onions and shredded nori if desired, and serve hot.