Nichirin Sword

Nichirin Blade is a special blade used for various cutting weapons of the Demon Slaying Corps, mainly being used in swords (called Nichirin Swords) to slay Demons. They are made of metal ore, which constantly absorbed sunlight, making them the only effective demon slaying weapon due the fact that other weapons may cut, but not kill the demon.

Additionally, the blades change their colour depending on their individual owner on first contact, giving them the name "The Blade of Colour Change" or "The Colour Changing Sword" (referring to the Swords with a Nichirin Blade).

Forging Process
Nichirin Blades are forged with Scarlet Crimson Iron Sand and Scarlet Crimson Ore, both of which are found on high mountains like the Sunlight Mountain, which is perpetually bathed in sunlight all throughout the year.

Demon Slayer recruits choose their own ore, after successfully attending the Final Selection. The ore then will be used by a swordsmith of the Swordsmith village for the forging process, which will later bring the weapon personally to the Demon Slayer.

Blade Colours
Nichirin Blades change colour depending upon the user and that makes them unique and special to each user, as each colour has a unique properties. They can be of many colours. Normally the blade has no stylized patterns and only the blade is a different colour. The only exception is Zenitsu’s blade which has a lightning bolt pattern.