This is one of my favorite dishes. I love curry so first time I saw it I totally though it was curry, but it wasn’t.
It is a very popular dish in Japan, but it is known as western food or Youshoku (洋食). The main ingredients can vary, but usually it contains beef, onions, mushrooms, demiglace sauce and tomato sauce. It is served together with plain white rice.
It is easy and quite to prepare and usually kids love it. As it is similar to curry, in Japan people eat it in curry specialized chains or restaurants.
Some people make it from scratch (as in the video I link). But the majority of people buy a package of roux because it’s faster to make an still delicious.
Link to the video recipe in English.