Thread: Carrying a Kamisori/knife in Japan

I'd advise to not "f*** around and find out" on this one.
He buys from the store and makes sure it's sealed somehow until he leaves the country.

Regardless of blade length, all knives are prohibited from carrying, except for lawful purposes. Such purposes include duty, work, or outdoor activities such as hunting, fishing, camping, hiking, etc. Blade length applies only to the illegal carrying of knives. A blade length of over 6 centimetres (2.4 in) becomes a violation of the jutouho 銃刀法 (gun and sword law), whereas under 6 cm (2.4 in) is a violation of the keihanzaihouihan　軽犯罪法案 (minor law violation). The former carries a heavier penalty than the latter. So unlike some other countries, blade length does not establish a right to legal carry. It only establishes the charge and degree of penalty. However, in practice, carrying alone is generally considered a minor crime unless used to carry out a criminal act.

You have to consider that being a "gaijin" (foreigner) will make it double or nothing.