Yori is a second-generation Japanese-British citizen, her parents having moved to London, England from Taketomi, Okinawa, Japan. Even in Japan, her family had been relatively middle class, with Yori's grandfather in a slightly upper class position for his time in politics. Her parents had only been married for about two years before they had moved to London.
Though it came with difficulty, Yori's family is relatively easygoing about the manners of her home, what with two of their children turning out to be capable of magic. There isn't much that come as a surprise to them, even though they have some difficulty understanding the wizarding world.