Many Japanese Restaurants are found in Japan. There are shops that specialise in: Sushi, Soba, Udon, Ramen, Curry, Yakitori, Tempura, Tonkatsu for example, and there are also restaurants such as: Izakaya, Family Restaurant, Shokudo. One can find not just Japanese cuisine, but other countries and even Vegetarian restaurants too.
Japan is famous for being clean, having great customer service and amazing food. Knowing this, it should come as no surprise that even at a truck stop, those places where one might find themselves in the middle of a long drive in need of a cheap and terrible coffee, Japan absolutely has you covered.