Boy, Demon Slayer or Kimetsu No Yaiba really is the new hotness. So big in fact that it's beating out One Piece in certain ways, a franchise with hundreds of games under its belt. What do we mean by that? Well, it's a Shonen manga adapted into an anime made by UFOtable that took off recently thanks to some amazing storytelling and stellar animation! Plus, there are tons of twists and turns.
Tanjiro is a Demon Slayer, as much as he doesn't want to be, and these swordsmen are only able to defeat demons thanks to their Nichirin Blades, otherwise known as Color Changing Blades. These weapons are honestly still underexplained even during the current manga arc, and not much is known about their qualities or smelting process. So, let's take a look at the prized possession of all Demon Hunters, and see what we can dig up.
10 They Aren't Only Blades
Now the name might confuse you, but Nichirin "blades" don't actually need to be swords. The reason they can kill demons is because of the sunlight they absorb, so the actual shape of the weapon doesn't matter. Now, something that can actually cut seems crucial, but Demon Slayers could use a Nichirin spoon if they wanted to. We don't see many examples of it in the show, but there are one or two in the manga. Gyomei, the Rock Pillar, is the primary example of this. The blind monk uses an ax and chain ball weapon that seem to kill demons. So, we can only assume he had those specifically crafted for him. Honestly, it's a big reason to read the manga over the anime, so you can see Gyomei in action early.
9 The Color Corresponds To The User's Breath Style (Usually)
Color Coordination is important in Demon Slayer, and that only becomes clearer as time goes on. Zenitsu has yellow hair because of his Breath of Thunder, Tanjiro's is Red because of his hidden history with the Breath of The Sun, and most of the Pillars have this similarity as well. But, it's not just hair, the color of the blade can usually be attributed to the style of Breath as well. Yellow is Thunder, Red is flames, blue is water, green is wind and so on. All of the pillars have color in their blades the correlates to their Breath Style, yet Tanjiro's blade is black...why is that? Hmm.
8 The Depth And Amount Of Color Is Also Important
Something else that hasn't been 100% confirmed, but makes a lot of sense, is the depth of color in the blade. Color changing blades don't just become a sword entirely painted a certain color. sometimes they do, but mostly it's little hints or patterns of color. Zenitsu, for example, has a blade with a lightning bolt of yellow across it.
It's not tons of color, but that's because Zenitsu isn't especially connected to his Breath Style, it was something that was forced on him. Others have more color, Tanjiro's entire blade is black, and even Giyu's blade isn't entirely blue.
7 The Only Change Color Once (Mostly)
Another thing about the swords that many people probably assumed was common knowledge is the fact that they only change color once. These aren't mood rings, they change color initially and then never again (except for one specific example with Tanjiro). So, once it's done its business, the color is locked in! Luckily, the series has never had a Breath user who had a blade, then switched Breath styles while keeping the same sword, because hoo boy would that get confusing. But, if new anime kids were expecting these swords to change colors as the users grow, that's not what Demon Slayer has in mind.
6 Every Demon Slayer Has Their Own Nichirin Artisan
Much like a knight needs an armorer, a samurai needs a katana artisan. And, luckily, Demon Slayer has an entire village of them. An arc that occurs later in the manga actually takes place entirely in this village. So, with every demon hunter, comes a swordsmith. They're assigned as soon as a Slayer's first blade is crafted, and they're the ones to craft all their blades from then on.
So far we've only seen 2 of them, but we can confirm that yes, most of them are as eccentric as Haganezuka, the swordsmith who tried to kill Tanjiro for breaking his blade. And yes, they all wear masks. It makes us wonder just who were the swordsmiths assigned to all the fodder Demon Slayers we've seen so far.
5 The Black Blade Has A Story To It
Tanjro's Nichirin Sword seems to be special, though that honestly might be his blood rather than the sword. Tanjiro is descended from a line of warriors who use the Breath of the Sun. And, there have been moments where Tanjiro's blade goes from pitch black to a vibrant red, almost as if it's been pulled straight out of the forge. Tanjiro's immediate family are coal harvesters, and his own name translates to a coal-furnace or charcoal itself. So, this charcoal-colored blade that turns bright when exposed to heat is actually more much fitting for our protagonist good boy than people may have thought.
4 They're Not ID Locked To Their User, Demons Could Use Them If They Wanted
Like we said before, blade color usually represents the breath style of the user, and blades can't change color more than once. Because of these two factors, people have unconsciously associated Slayer's blades with the users themselves. But, remember, they're just tools. Slayers can use any other slayers sword, and they aren't at all locked to any specific fighter. Heck, a demon could use one of these swords if they wanted to. There's nothing that makes them specifically dependant on Demon Slayers, it just so happens these warriors are the best people to make use of them is all.
3 They're Made From Scarlet Ore
First and foremost, we should probably talk about how these swords are made. These blades aren't ordinary iron or steel, they're actually crafted from a fictional ore called the "Scarlet Ore" that can be found on Sunlight mountain. Because this place is so constantly exposed to sunlight, the ore itself has absorbed the UV energy and holds it tight even when forged into a blade.
Now, the name is Scarlet Ore, and while that may suggest fire, Scarlet or Crimson actually tie closer to the Breath of the Sun. We're fully speculating here, but maybe the Ore has a connection to the original style of Breath or something.
2 They're Basically UV Batteries
Like we said earlier, these blades don't actually exude this sunlight energy when swung. It's more like they're batteries, and the energy contained inside them is lethal on contact with a demon. That's why we don't see any of the Demon Slayers using ranged "sunlight" attacks or anything like that. Demon Slayer might have supernatural elements, but the entire premise is very much built on a foundation of reality. Still, it makes us wonder, is there anything in this universe that uses Scarlet Ore like a battery of sorts? We know that the Wisteria flower can also harm demons as well, but we'd love to see some other inventions that use either of these weaknesses as a base.
1 They're Not The Only Demon Killers
Finally, there's no better way to end a discussion about what Nichirin blades are, then to summarize what they aren't. And one thing that constantly surprises fans of the series, is that the blades aren't the only thing that can kill demons. First of all, demons can kill other demons! Secondly, Muzan's blood is both a steroid and a lethal poison to demons in certain doses. Third, direct sunlight or even UV lightbulbs (if they existed) kill a demon outright. And lastly, the Wisteria flower is commonly used as a way to ward off demons, but it can also kill them when mixed into a poison. Flower Pillar Shinobu was known for this, and this poison actually plays a huge part in taking down one of the Upper Moons later on.