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 cooked rice along with the mentsuyu. Mix well.