In a mixing bowl, combine mirin, minced garlic, grated ginger, sesame oil, and soy sauce. Stir well to create a flavorful marinade. Add the top sirloin and marinate for 30 minutes.

While the beef marinates, prepare the fried rice. If using frozen rice, heat it as per package instructions. For homemade, heat a large skillet over medium-high heat, add oil, and stir in cooked rice for 3-5 minutes until heated through.

In the same skillet, heat oil over medium heat. Add sliced carrots, zucchini, and mushrooms, stir-frying for 5-7 minutes until vibrant and tender.

Remove the marinated beef and let it sit at room temperature for 5 minutes. Sear the beef in the hot skillet over medium-high heat for 5-7 minutes until cooked to your preference.

To assemble, spoon fried rice into bowls, layer sautéed vegetables, and top with sliced beef. Drizzle with remaining marinade, serve hot, and enjoy!