01 - Rinse Japanese rice under cold water until water runs clear. Combine rice and water in a pot or rice cooker. Cook according to appliance instructions, or bring to boil, cover, and simmer over low heat for 15 minutes. Let rest covered for 10 minutes before serving.
02 - Whisk together rice vinegar, sugar, and salt in a small bowl. Add sliced cucumber and julienned carrots, toss thoroughly to coat, and allow to marinate for at least 15 minutes before serving.
03 - Pat fish fillets completely dry with paper towels. Brush with soy sauce and mirin mixture. Heat vegetable oil in a nonstick skillet over medium heat. Place fish skin-side down and grill for 3-4 minutes per side until cooked through and golden brown. Remove from heat and set aside.
04 - Beat eggs with soy sauce until well combined. Cook in a small nonstick pan as scrambled eggs or as a thin omelet. If making omelet, slice into strips before serving.
05 - Portion cooked rice into each bento box or plate. Sprinkle with toasted sesame seeds and nori strips. Arrange grilled fish, pickled vegetables, prepared eggs, avocado slices, steamed edamame, and apple slices alongside the rice in each container.
06 - Serve immediately while warm, or allow to cool completely, cover tightly, and refrigerate for a convenient portable breakfast option.