You cannot legally carry a sword in Japan as it's illegal to carry a sword or blade of any kind that exceeds 6cm without any justifiable grounds due to the Swords and Firearms Control Law.
Anyone that violates the law faces imprisonment with work for up to 2 years and or a fine of 300,000 yen.
Katanas also known as Samurai swords are not illegal in the U.S. as long as you're 18 years of age or older.
If you're at least 18 years of age or older you can legally possess a Samurai Sword or Katana.
Although the ownership laws of a Samurai Sword or Katana vary from state to state but most states do allow you to own and even display a Samurai Sword.
However there can be restrictions on carrying the Samurai Swords or Katana in public.
In many places, the possession and transportation of weapons, including swords, may be regulated or restricted by law.
Carrying a sword in your car could potentially be seen as carrying a weapon, and it may be subject to the same regulations that govern the possession and transportation of weapons in general.
Real Katanas and Samurai Swords are very expensive and often, they cost around $10,000.00 to 25,000.00 and more.
In general, Katanas and real Samurai Swords are very expensive, and when it comes to an authentic samurai Katana, things get even more expensive.
Compared to Chinese productions, prices usually vary between $1,000.00 and $4,500.00 for an object considered "reasonably traditional".
With a precise and well-executed technique, a katana can potentially cut through bone, especially if the bone is relatively thin or if there is sufficient force applied.
However, it's worth noting that cutting through bone is not the primary purpose of a katana.
Authentic, antique katanas, especially those crafted by renowned swordsmiths tend to hold their value and fetch higher prices.
Their value lies in their historical significance, age, and the legacy of the swordsmith.