I have bought 2 kitchen knives in Japan and flewn home with them in my checked luggage - I declared them but since my total was under the limit both times I've payed no duty on either.
I also have ordered quite a few things from Japan - one time I had to pay an admin charge for customs - basically if you get unlucky and they inspect your container you get charged - this was via FedEx. I'm told the odds are much lower other methods of shipping