In a mixing bowl, combine mirin, garlic, ginger, and sesame oil.
Add the cubed sirloin steak and toss until evenly coated.
Cover and refrigerate for at least 30 minutes to allow the flavors to develop.
While the steak marinates, wash and prepare the vegetables.
Heat a large skillet over medium heat with a small drizzle of oil.
Add the carrots, zucchini, and mushrooms.
Sauté for 5–7 minutes until tender and lightly browned.
Increase the heat to medium-high.
Add the marinated steak and cook for 4–5 minutes, stirring occasionally, until it reaches your preferred doneness.
Combine the cooked steak and vegetables in the skillet.
Divide the fried rice among serving bowls.
Top with the steak and vegetable mixture.
Drizzle with soy sauce and serve immediately.
These Hibachi Steak Bowls are best enjoyed hot, straight from the skillet.