Demon Slayer: Kimetsu no Yaiba describes the battle between the Demon Slayer Corps and the demons. As the Demon Slayer Corps is organized under Family Ubuyashiki, the demons also have an organization. By learning the organization of the demons, Demon Slayer: Kimetsu no Yaiba will be more interesting.
Demons in Demon Slayer: Kimetsu no Yaiba are creatures which live on human blood. They have regeneration capability; if they are injured or lose part of their body, they can regenerate by themselves. Either the sunlight or slicing of their head by a special sword called Nichirin blade can end their lives.
See the related article:
Muzan Kibutsuji is the demon who massacred Tanjiro’s family.
In this world, there is only one demon whose blood flowing in its veins has the power to turn humans into demons. This person was, approximately one thousand years ago the first individual that became a demon. It’s also the enemy of your family, Tanjirou. Also I think it knows how to turn your sister back into a human. This demon’s name is…KIBUTSUJI MUZAN.Explanation by Sakonji Urokodaki, Demon Slayer: Kimetsu no Yaiba Comic 2, Chapter 11
says Sakonji Urokodaki, the trainer of Tanjiro, as Nezuko has become a demon.
Find out who Sakonji Urokodaki is in the related article:
Is it only me who thinks that Muzan Kibutsuji resembles Michael Jackson in Smooth Criminal costume?
How Muzan Kibutsuji turned into a demon
The person who turned Muzan Kibutsuji into a demon was a generous doctor, who was trying to improve the health condition of Muzan. Since he was born, Muzan was in poor health. He was frustrated as his health condition was not getting better and killed the doctor. After that he realizes that the medicine which he was getting from the doctor was actually working. But there was a problem. He could not walk in the sun. The medicine was apparently made from blue-colored spider lilies. But he could not find it.
Muzan Kibutsuji wanted to obtain a perfect body, so his priorities have always been:
1) to find the blue spider lily and
2) to make a demon who can withstand the sun, as Muzan can overcome the sunlight by taking those demons into his body.
Capabilities of Muzan Kibutsuji
Muzan Kibutsuji has the following capabilities:
1) Blood which turns human into demons
2) To pretend to be a human being
3) To read a thought of demons which are close by
4) To spot the location of demons
except Tamayo and Nezuko who managed to escape from his pursuit
If demons speak about Muzan Kibutsuji, their bodies will be destroyed
Muzan Kibutsuji’s relation to The Demon Slayer Corps
Needless to say, The Demon Slayer Corps and Muzan Kibutsuji have hostile relations with each other. But actually it is more than that. In the end of the Entertainment District Arc Kagaya Ubuyashiki says:
We will definitely defeat you within our generation. YOU ARE THE SINGLE BLEMISH ON OUR ENTIRE FAMILY.Kagaya Ubuyashiki, Demon Slayer: Kimetsu no Yaiba Comic 11, Chapter 97
Yes, the master of The Demon Slayer Corps, the Ubuyashiki Family and Muzan Kibutsuji are related by blood! The story is getting more and more exciting, isn’t it?
When watching Demon Slayer: Kimetsu no Yaiba, you sometimes hear “Twelve Kizuki”. In Japanese language it is “Juni Kizuki (十二鬼月)” and literally means “Twelve Moons of Demons”. These are the twelve most powerful demons which are under the direct command of Muzan Kibutsuji. They have become demons by withstanding the large portion of Muzan Kibutsuji’s blood. There are six upper rank demons and six lower rank demons, Upper Rank One being the strongest.
Upper Rank Demons
In Japanese upper rank demons of Twelve Kizuki are called “Jogen (上弦)”. The Upper Rank Demons have the kanji character for Upper Rank in their right eye and their numbers in their left eye.
Upper Rank Demons are so powerful that they sometimes defeat Hashira. There has been no change in Upper Rank Demons for more than 100 years until the defeat of Gyutaro and Daki.
Lower Rank Demons
In Japanese lower rank demons of Twelve Kizuki are called “Kagen (下弦)”. The Lower Rank Demons have their ranks and numbers engraved together in one eye.
They use Blood Demon Arts as Upper Demons also do, but the level of power is much lower compared to Upper Rank. It seems that it is not too difficult for Hashira to defeat Lower Rank Demons.
Relation to the Moon
The words “Jogen (上弦)” for Upper Rank and “Kagen (下弦)” for Lower Rank actually refer to the phases of the moon. The first quarter moon is called “Jogen (上弦)” and the last quarter moon is called “Kagen (下弦)”. The kanji character “弦” means a bowstring – “Upper” with bowstring up and “Lower” with bowstring down.
Why “Twelve” Kizuki?
It is not explained even in the fan books why there are “twelve” most powerful demons. Considering that Twelve Kizuki literally means “Twelve Moons of Demons”, it might be natural to conclude that it is because twelve months make one cycle of the year. Or we could also say that the Twelve Kizuki are similar to the Twelve Apostles of Jesus. It is up to you how to interpret the number twelve.
Demon Slayers fight against demons with Nichirin Blade made from the metals that have absorbed the sunlight. The Demon Slayer Corps is the sunny side and the demon’s organization is the dark side of the story. It is very interesting to see it as the contrast between Sun and Moon. Great work of Gotouge Sensei!