When you are in Japan, and fed up eating Japanese foods, why not trying McDonald's?
Offers are different from those offered in Europe. Especially Teriyaki burger is most famous local burger sold in Japan. This burger comes with lettuce and sweet teriyaki sauce.
The first restaurant opened in Ginza district of Tokyo in July 1971. The number of restaurants is 2910 in Dec 2019. This number is after USA, which is the second in the world. Japan has roughly 500 more McDonald's restaurants than in China and double more than in Germany which is 4th place in the world.
By the way, there are many other hamburger fast food chains in Japan. Mos Burger and Freshness burger are the examples of the local chains.