Curry has an interesting history in this country. It was adapted by the Imperial Japanese Navy during the Meiji Era (1868-1912) as a food which could be made aboard ship to keep the ship's crew healthy.
Curry was adopted from the influence of the Royal Navy. Friday was the day curry rice was served in the IJN. After the formation of the Maritime Self Defense Forces, Friday once again became, curry day.
Curry in Japan comes from 3 main sources:
Japanese curry, usually curry powder mixed with Apple sauce. These are sold in supermarkets. It's a block of curry powder, spices, apple pulp. Many households will stir fry pork or chicken then add onions, carrots and potatoes. The curry mix, known as roux is then added with water, brought to a boil, then served over white rice. As well, curry rice is a very popular food in school lunches. It is also served as curry udon, or put in dumpling and deep fried. There are also boil in the bag versions which can be used on camping, work lunches or emergency foods during diasters.
Indian curry from the many Indian/Nepalese restaurants. These have become nearly ubiquisous throughout the country. I cook either Sharwoods, Pataks or Asian Home gourmet spice pastes.
This one on the stove was a Patak's Very Hot Curry paste.
Thai curry. These are typically spicy combining spices from South-East Asia, with shrimp paste, as well as coconut milk.