Heat salad oil in a frying pan over medium heat. Add the beef and stir-fry until the color changes. Add yakiniku sauce and cook until the liquid evaporates.

In a bowl, combine the cooked rice, stir-fried beef, and white sesame seeds. Tear the cheese slices into small pieces and mix gently. Divide the mixture into 4 portions. Place each portion on a piece of plastic wrap, shape into a triangle, and wrap tightly to form rice balls.