Nichirin Blades are special blades used by and made specifically for the Demon Slaying Corps to slay Demons. They are forged from a unique ore that constantly absorbs sunlight, one of the only major weaknesses of Demons. Therefore, decapitation by Nichirin Blade is one of the only ways a human can kill a Demon, the other being the use of a Wisteria-poison coated weapon.

Nichirin Blades take on a distinct color when first drawn by its owner, which is why they are also referred to as "The Color Changing Swords". However, the holder is required to have a certain amount of skill, or the blade will not change color.

Nichirin Green Blade The Breath of the Wind style are associated with the green-colored Nichirin blade. Breath of the Wind is another of the five main styles used by the Demon Slayer Corps. With eight fighting moves, Breath of the Wind is a potent method with a good range of uses. One wielder of a green blade is Sanemi Shinazugawa.