Kimetsu no Yaiba: Nichirin Blade, Weapon Of The Demon Slayers
Every artisan needs their brush and every combatant needs a weapon, it is their tool which bridges the gap between humans and their physical limitation as well as helps them accomplish tasks that would otherwise be difficult. Those that call themselves demon slayers are predominantly humans for the most part and given that demons are often supernatural beings with strength far beyond humans, it stands to reason that the corps members would need a tool to help bridge this gap and in Kimetsu no Yaiba this is where a Nichirin Blade comes in.
Demons have great regeneration abilities with exceptionally powerful demons being able to heal themselves from even the most fatal of wounds in the matter of seconds. As such, a standard sword can cut them just fine but would be useless as most demons can just heal themselves back up. Higher ranking demons can even outright block standard steel with little to no damage due to their higher strength.The one weakness that demons have however is to the sun which burns them as long as they are exposed to it and even limits their regenerative abilities.
In Kimetsu no Yaiba the Nichirin blade is a weapon unique to the demon slayer corps and are forged from Scarlet Crimson iron sand and the Scarlet Crimson Ore which are found on high altitude mountains that are constantly bathed in sunlight. This ore continuously absorbs and can retain sunlight and when forged into a blade, allows that blade to have the same properties. The ability of the blade to harness and exhibit the properties of the sun is what makes it an extremely suitable weapon to combat demons as when they are cut by it their regeneration and healing is limited similar to if they were exposed to sunlight itself. This allows any form of attack to be much more fatal to demons and when cut at the neck bone can permanently kill them.
The blades are forged by very experienced bladesmiths from the hidden swordsmith village who have trained and honed their craft for many centuries. Typically a prospective demon slayer is awarded an ore after completing their final selection. They are allowed to choose a single ore from several choices and once they are happy with their choice it is then passed to a swordsmith to be crafted. Once the blades are ready the swordsmiths themselves will personally deliver the blades to the demon slayer.
In the event that a blade becomes damaged or even broken, the same swordsmith will reforge the blade for the same user seemingly creating a lifelong relationship between the swordsmith and demon slayer. Although as we’ve seen these blades are considered a one time production and any break or chip in the blade is not typically well received by the swordsmith. While the blades are made of extremely rare and high quality materials they are not indestructible and can break if mishandled by their users. Kanjiro has broken a total of 3 during his tenure as a Demon Slayer even though this is likely seen to be not a very good practice and is more a reflection of his inexperience with the blade.
Each Nichirin blade in Kimetsu no Yaiba is unique in appearance as each sword will adopt a different colour depending on its user and is why they are also known as the colour changing swords. They adopt this colour when their user first unsheathes the blade but requires that they at least have some level of skill before changing permanently. Each colour is said to have different properties likely to be inline with the user themselves with some swords having a pattern along its blade instead of fully changing in colour. The colours also may correspond with the breathing style the user might use such as the blade of a water breathing style user turning blue while a flower style user may have a pink blade.
Each colour has an associated attribute attached to it but the colour black seems to be the least known colour variant. Most consider it a bad omen if one receives a black bladed sword as it seemingly implies the user will not go far as a Demon Slayer. Kyojuro Rengoku even mentioned that there are no known black blades in the current Hashira ranks.
The blades can also be unique in other aspects not just the colour of the blades and can be forged to meet the needs of the users which shows the skill of the swordsmiths. Several Hashira members use unique swords and weapons based on their styles such as Obanai’s Kris sword, Gyomei’s Axe, chain and mace combo and Kanroji’s flexible whip sword. This shows that the materials are flexible enough to assume multiple different shapes and still retain their sun absorbing properties. Even the upper rank demon Kokushibo utilized a Nichirin blade when using his Moon breathing style but the blade was further augmented with his own demonc powers allowing them the ability to change shapes and regenerate.
Another unique aspect of the Nichirin blade is that they are able to glow red under certain circumstances which have not been fully explained. Some members of the hashira have achieved this by hitting their blade against another user while others have turned their blades red by applying an extremely strong, vice-like grip to the handle. The unique properties of this red glow is that it allows the user to completely halt the regenerative capabilities of demons. Earlier I mentioned that the nichirin blade can already do this but that only applies to generic demons. Higher level demons can actually circumvent this as their regenerative capabilities are extremely high. This red glow state is still somewhat a mystery but likely a product of generating a high temperature within the blade through friction or other means.
Overall this weapon is the epitome of the weaponry accessible to the Demon Slayers and shows how a simple tool can help humans to overcome supernatural and superpowered demons in their war. The nichirin blade is the perfect tool for the demon slayers and represents the simple yet unwavering strength of the Demon Slayer corp in fulfilling their mission of making humanity safe from Demon attacks.