If you are flying out of Narita, you will have a really hard time getting through, but then again you might not. I took back a small katana. When I bought it the guy told me it was a "paper cutter" or an envelope opener, but the tip of the blade was so sharp it could slice open your finger. That made it through customs, and the x-ray machine etc, but 2 lighters I had bought at a local 100Yen shop didn't... but I do know that if they find anything that is "dangerous", they take it away. I don't know 100% if they ship it to you anyway because my boss had the same problem, and she's never seen her knife since.
Best bet, ship it... don't bring it on the plane or put it in your luggage...
good luck