Better start registering those swords.
The Japanese Sword Law
In order to legally own a sword in Japan it has to be registered in accordance with the Ju-tô-hô 銃刀法 (Japanese Firearms and Sword Law). This applies to both antique and newly made swords (Shinsakutô 新作刀). Exempted are blades under 15 cm (5.9 inches), and Iaitô / Mogitô (training and decorative swords made from a zinc-aluminum alloy that can't be sharpened). Presently about 2.3 million swords are registered in Japan.