i thought japanese curry was one of those "white people foods" from the meiji era that japanese people thought was the reason white people were big and tall and successful. so because the brits looked at the rich and extremely varied culinary traditions of india and said "it's all bits of veg in yellow gravy innit" and then made a dish called curry consisting of bits of veg in yellow gravy, the japanese saw the british sailors eat that and made their own version