1. Wash rice until water is translucent. Cook in rice cooker or on stovetop according to directions.
2. Saute onion in oil. Add chicken cook through. Add soy sauce, sake, and mirin.
3. Increase heat to high and add eggs to cover the whole pan. Place a transparent lid on top to let the steam cook the egg for a couple minutes before turning off the heat and stirring everything together gently.
4. Serve chicken mixture on top of rice. Garnish with scallions, if you like. Other garnishes could include chili flakes, sriracha, or simple salt and pepper.