Multiverse Headcanon

The colour of the blades

The blade takes its colour from the personality of its owner

Tanjirou’s blade is one of the biggest mysteries of KNY because of his colour. Y’all know that his blade turned black when he received his katana.

Everyone thinks it an extraordinary thing because of his rarity but we can read that they are a little bit disappointed. They think the blade will take a red colour like the Tanjirou’s hair and eyes because he’s a child of brightness

In the manga, the black blade is described as an unlucky sign, the owner is doomed to be forgotten.

But what does it really mean ?

The blade takes its colour from the power of its owner

When Giyuu has to get another katana for continue to fight against Muzan, he has to take one with a blue blade, like his first one.

So, we can say that after a blade takes its colour, only slayer with a katana in the same colour can use it.

Tanjirou’s blade is black because he can manipulate many elements

Black isn’t a real colour so the blade hasn’t really been personified and takes a final element. So Tanjirou can use different techniques like water and fire.

The blade become red when the slayer get the mark

Yoriishi, the swordsman with the original breath, hasn’t yet been colorised with his katana, so because he had the mark, his katana must be red.

looks coward but becomes badass when he fights

Just wants to protect his friends

Gets mad if you hurt his friends

Nezuko : I thought ''nezu'' came from the word ''nezumi'' which means mouse in Japanese and ''ko''means child. So we can say that Nezuko means ''mouse child''. This makes sense since she can become smaller with her demon powers.

Inosuke : ''Ino'' could coming from ''inoshishi'' which means boar in Japanese, and maybe ''suke'' is kind of related to child or son idk. It can completely be true because Inosuke grew up with boars as a family, and where is his freaking boar mask coming from ?

Zenitsu : ''Zen'' means you know, zen, like when you are in peace with yourself and you being calm you don't even know why. And ''itsu'' is ''when'' in Japanese, so maybe the name means ''When are you zen ?''. It is ironic because Zenitsu is the character who is the most scared of the death.

In conclusion,

GUYS THIS IS A COMPLETELY WRONG THEORY WHEN YOU CHECK IT OUT ON INTERNET THE MEANING ARE FAR AWAY FROM WHAT I JUST WROTE !!

WHEN I WAS THINKING OF THE THEORY IT WAS LATE IN THE NIGHT, I DID THAT JUST FOR THE JOKE OK ?