Japan has some of the best food on the planet. Foreign cuisine is very popular, particularly Korean, Chinese and Italian, and foreign restaurants abound everywhere and are much the same as the restaurants you would get home. Often the menu will be in Japanese only, so you may need to get help from the waitress as to what each dish on the menu is. There are also plenty value for money family restaurants such as the Gusto's and Denny's chains. With these, although the "home cooking" element is certainly NOT there, neverthless they are cheap and you can usually get unlimited tea/coffee for a few hundred yen. Lastly, there are the fast food restaurants such as Macca's and KFC, basically the same as what you get back home, albeit with somewhat smaller portions.
This is what you come to Japan for, not to eat that crappy fast food. So break out of that comfort zone and try something new! There are many different styles to the ones below, but this will give you an idea.