Marinate the steak by combining mirin, minced garlic, grated ginger, and sesame oil in a mixing bowl. Add cubed sirloin steak to the bowl, coat well, cover, and refrigerate for 30 minutes.

Prepare the vegetables by washing the carrots and zucchini, slicing the carrots thinly, cutting the zucchini into thin rounds, and quartering the mushrooms.

Sauté the vegetables by heating a drizzle of oil in a large skillet over medium heat, adding the carrots, zucchini, and mushrooms, and sautéing for 5-7 minutes until tender.

Cook the steak by increasing the heat to medium-high and adding the marinated steak to the skillet, searing for 4-5 minutes until browned.

Combine and serve by mixing the sautéed vegetables and beef together in the skillet, serving over fried rice, and drizzling with soy sauce.