Katanas are not illegal in Japan, but their possession and sale are subject to strict regulations under the Sword and Firearms Control Law (刀砲刀剣類所持等取締法, Tōhō Tōkenrui Shoji-tō Torishimari Hō).

In Japan, the ownership and possession of certain types of swords, including katanas, are allowed, but they require appropriate licensing and registration. The law categorizes swords based on their historical or cultural significance. Genuine antique swords that hold historical value, such as those recognized as Important Cultural Properties or National Treasures, are generally allowed for possession and sale.

However, the possession of non-traditional swords, replica swords, or modern-made swords without significant historical value may be restricted or prohibited under the law.

To legally possess a katana in Japan, individuals, both Japanese citizens and foreigners, must adhere to specific procedures and obtain the necessary permits. This typically involves obtaining a sword possession permit (To-ken Menkyo or To-ken Tōroku) from licensed dealers or the Japanese government authorities.

It's important to note that the specific regulations and requirements for owning and acquiring katanas can vary depending on factors such as the type of sword, its age, and other criteria. To ensure compliance with the regulations and to obtain accurate and up-to-date information, it is advisable to consult with Japanese government authorities, such as the local police or the Agency for Cultural Affairs. They can provide the necessary guidance on the possession and sale of katanas and help navigate the legal procedures and permits required.