Fried rice is actually a Chinese food. However, as like ramen noodle, it is not considered so much as Chinese cuisine in Japan. Then, I assume that the consumption is higher in ramen noodle bars/diners than in Chinese restaurants.
Then, not like to in Chinese restaurants in Europe, fried rices are served at semi-sphere shape. The ingredients are depended on the diners but usually egg, scallion, meat(pork)/seafood(shrimp), and green peas. It is common to have fried rice with chicken or beef in Europe but fried rice with chicken or beef in Japan is very rare.
Diners where offer ramen usually offers half size portion for customer who cannot eat the regular portion together with the ramen. Therefore a lot of people order ramen and a half size fried rice. Then, it is interesting that no diner offers half size ramen. Therefore no one can order regular size fried rice and half size ramen. However, there are many customers who just order regular size fried rice!
Then, there are many diners or restaurants specialized in ramen noodle throughout Japan but I never heard any restaurants which offer only fried rice. However it does not mean that fried rice is unpopular but it is very strange.