Not a country that you traditionally associate with curry? Curry was imported into Japan by the British during the Meiji era which is why the Japanese consider it a Western dish and not an Asian one.
Japanese curry is quite different from most other curries of the world — it has a thicker consistency and the taste leans on the sweet and savoury side. The sauce is rich and thick, and layered with spices with a hint of sweetness. It is a lot less spicy than most curries.