Japanese cuisine is not just traditional dishes as like sushi or tempura but also includes contemporary dishes which appeared in early twentieth century.
These contemporary dishes are adapted from cuisines from Europe and called "Yoshoku" - western food. For example, Japanese curry with rice is not an adaptation of Indian curry but British style curry. Napolitan, a fried spaghetti with ketchup is a typical version of Japanese pasta. Napolitan can not be found in Naples or any other places in Italy.
Cream stew is also a yoshoku dish. It is a white stew consisting meat(pork or chicken), various vegetables(mostly carrot, onion and potato, as same as Japanese curry) and cooked in thick white roux.
Then, not like beef stew which can be found at restaurants and yoshoku diners, cream stew is hardly to be eaten at restaurants. The preparation is not so difficult as beef stew or eaten all year round as curry with rice, cream stew is a typical seasonal dish eaten mostly in winter.
My entire life, living more than 46 years, not only I have never ate cream stew at restaurant but also never saw cream stew on menu. Therefore it is extremely rare to encounter cream stew during your stay in Japan but if you see it on the menu, you must try it.