Yes, foreigners can buy swords in Japan, but there are certain regulations and procedures that need to be followed. Traditional Japanese swords, known as katana, are considered cultural artifacts and are subject to strict regulations in order to preserve their historical significance and ensure responsible ownership.

To legally purchase a sword in Japan as a foreigner, you will typically need to follow these steps:

1. Obtain a "sword possession permit" (To-ken Menkyo or To-ken Tōroku), which is required to own a sword in Japan. This permit can be obtained from the Japanese government or through a licensed dealer.
2. Find a licensed dealer or a shop authorized to sell swords. These shops are knowledgeable about the legal procedures and can assist you in obtaining the necessary permits.
3. Provide identification and proof of address. You will need to present your passport or residence card and proof of your current address in Japan.
4. Complete the required paperwork, which includes the application for the sword possession permit and any additional documentation requested by the dealer or government authorities.
5. Pay any associated fees, including the cost of the sword, permit fees, and administrative charges.

It's important to note that certain types of swords may have stricter regulations due to their historical or cultural significance. For example, swords classified as Important Cultural Properties or National Treasures may have additional restrictions on ownership or export.

It is highly recommended to consult with the Japanese government authorities or an authorized dealer for detailed information and guidance on purchasing swords in Japan as a foreigner.