Nichirin Blade is the name for the swords used by the Demon Killing Corps. Due to changing color depending on who their owner is, they are also known as The Blade of Color Change.[1]
Description
While the blades look like normal swords, they have many special properties. The metal the blades are made of is the only mineral that is capable of cutting through a demon’s neck and decapitating them. The swords are taking different colors depending on the user. Either fully, like Tanjirou’s black sword, or partially, like Zenitsu’s yellow sword.
Forging Process
Nichirin Blades are forged with Scarlet Crimson Iron Sand and Scarlet Crimson Ore, both of which are found on the Sunlight Mountain, which is perpetually bathed in sunlight all throughout the year.[2]