If you are traveling Europe, it is quite easy to find a place to eat. The reason is that the restaurants,cafe or diners are all the time located on the ground floor or basement with direct access from the street, excluding roof top or restaurants located on the top of the building.
On the other hand, there are many restaurants located on first floor, second floor, third floor or other floors in Japan, especially in large cities. Also there are many buildings which numerous restaurants located in a single building. Therefore even you have the address of the restaurant, you have to carefully check the name and the floor.
Then, there are many restaurants which you can hardly find the places too. These restaurants can be without sign board or even do not look like a restaurant. Usually these places look like a ordinary residential houses and you will think that you cannot eat there. Also, there are many places which are not locating at the main street or street possible to access by cars on narrow alleys.
Sawada, a noodle diner in Iruma, Saitama prefecture is a good sample. It is located at the quite residential area of Iruma, surrounded by ordinary residential houses on a narrow street. Then the building looks like a normal house with no proper sign board. Of course no menu samples available outside the building.
Anyway, go inside and find a place to sit down and order the meal. You will get a nice udon and tempura like above.