In 1890, Tokyo University professor Basil Hall Chamberlain codified an entire generation's view of Japan in his "Things Japanese," a collection of descriptions and apercus subtitled "Being Notes on Various Subjects Connected with Japan for the Use of Travelers and Others."
In so doing, he also created the canon for "Japaneseness" and validated the uniqueness of what he canonized -- no matter that it had originally come from Korea or China or even further afield. Simultaneously, if inadvertently, he "taught Japan to the Japanese," as one commentator has noted.
Japan itself had no need of Japaneseness until only some decades before Chamberlain published his book, because a standard of comparison had not been necessary. Now it was -- the United States had intruded, breaking the locks and forcing the doors. Faced with their sudden national differences from the rest of the world, the Japanese found a need to classify and annotate themselves -- a process which, as international exposure has grown, has continued ever since.