The converse statement is something like "Japan is not an eastern society" which just sounds... laughably incorrect.
Of course it sounds ridiculous. Boolean algebra says the validity of a statement's converse is independent of the original. P → Q, tells us little about Q → P.
Is it really though?
You could make the argument. Japan was actively xenophobic and exclusionary to practically all but the Dutch. And after that their biggest influence was U.S. occupation during the 50s. Lots of “western” influence there.
(Obviously in actual critical work, the word western isn’t useful at all as it doesn’t have much meaning)
I'd say their biggest influence was Classical Chinese culture.