In 1949 Scene: The International East-West Magazine printed and article [Japan has a 'Valentine's Day'][1]:

After discussing similarities to " 'hoshi-matsuri' (Star Festival) or 'tanabata matsuri' ... celebrated July 7 " it is stated concerning actual Valentine's Day:

>...crude tokens of a lover's sentiments. American soldiers, for lack of anything else, send them to wives and sweethearts in the States. But some soldiers send them to their Japanese girl friends.  Most Japanese, however, never have heard of Valentine's Day and it is unlikely that they ever will.



  [1]: https://books.google.com/books?id=Bj4zAQAAIAAJ&q=japan%20valentine's%20day&dq=japan%20valentine's%20day&hl=en&sa=X&ved=0ahUKEwiJxbmbn8PLAhXDHh4KHVRPA88Q6AEISzAE