Nichirin swords are fictional weapons that originated from the popular manga and anime series "Demon Slayer: Kimetsu no Yaiba." In the series, Nichirin swords are said to be crafted from a special metal and possess unique properties that allow the demon slayers to fight and defeat demons.

While the concept of Nichirin swords is not based on historical or factual elements, they have gained significant popularity due to the success of the "Demon Slayer" series. Fans of the series may create replicas or fan-made versions of these swords for cosplay or display purposes, but they do not exist as authentic historical weapons.

It's important to distinguish between fictional weapons created for entertainment purposes and real historical weapons. The Nichirin swords are part of the fictional world of "Demon Slayer" and do not have any basis in historical Japanese weaponry or swordcraft.

If you have an interest in real historical Japanese swords, such as the katana or other traditional blades, there is a wealth of information available regarding their construction, history, and cultural significance. Reputable sources, museums, or experts in Japanese swordsmithing can provide valuable insights into the authentic traditions and craftsmanship of historical Japanese swords.

Always prioritize reliable information and enjoy the fictional creations of series like "Demon Slayer" within the context of their fictional universes.