Pat the steak dry. Sprinkle with salt and pepper. Cover with plastic wrap and let it come to room temperature.
Mix the soy sauce, mentsuyu, and 1 teaspoon of the raw garlic in a bowl.
In a large skillet, melt three tablespoons of butter. Add the ginger and the rest of the garlic. Sauté for a minute to crisp it up. Stir frequently and remove from the heat before it burns.
Remove half the garlic and ginger and set aside. Pour the butter and the rest of the garlic and ginger over the rice along with the mentsuyu. Mix well.
Heat the sesame oil in a cast-iron skillet over MED-HIGH heat. Add the steak to the hot pan. Cook for 3-4 minutes on each side. Then take it out of the pan and set it aside to rest.
Melt three tablespoons of butter in a pan. Fry the rice over MED-HIGH heat until it is a little crispy. Divide the rice between two bowls.
Cut the steak into cubes and place into the bowl with the soy, mentsuyu, and garlic mixture. Add the steak to the rice and top with the crispy garlic ginger and green onions.