Demon Slayer is one of the most popular anime and manga series of the decade. The series is a perfect blend of action, thrill, tragedy, comedy, suspense, and horror. Due to the popularity of the series, it broke the two-decade-long box office record of Spirited Away in Japan.
Before the release of Demon Slayer: Infinity Train, Spirited Away remained the highest-grossing anime movie in Japan, but shortly after the release of Demon Slayer movie, the tables were quickly turned.
The season of the series was but a prologue. It wasn't until the movie that the story finally started taking shape and gave away hints of the secrets behind the Kamado family.
Yoriichi Tsugikuni plays an important role in the plot development. He was only shown in flashbacks and wasn't featured much. But it was enough to reveal that he is the strongest character in the series. He was the sole reason for the existence of the Breathing Techniques, due to which, normal humans were able to fight immortal demons. This helped save thousands of lives over several centuries.
1. Yoriichi Tsugikuni Created the Breathing Styles
Yoriichi created the Sun Breathing Technique, having 12 forms. However, since it was hard to master, people started developing different breathing styles over the years with varying forms. But, all those breathing styles were the branches of this particular style.
Over the years, the Sun Breathing Technique was lost. So much so that it was difficult for Tanjiro to get any information about it even from the high-ranking members of the Demon Slayer Corps. As of now, only the Tanjiro family was shown to have carried on his legacy.
2. He was Able to See the Transparent World
This unique ability is known to be possessed by only those who had the Demon Slayer Mark. Except for him, Tanjiro's father could use it and Tanjiro himself learns it later on.
This ability allowed him to see the bodies of living things in transparency. Not only that, but he can also sense blood flow, muscles, and sudden movements of his opponents. Unlike others, who had to learn this ability, Yoriichi was the only one who was born with it.
3. His Hanafuda Earrings is Passed Down to Tanjiro
Yoriichi is the real owner of the Hanafuda Earrings worn by Tanjiro. Tanjiro's father gave it to him before explaining how the Hinokami Kagura and the Earrings are passed down to each generation of the Kamado Family.
In the eighth episode of the first season, we saw glimpses of Muzan's memory that traces back to over five centuries. There, Muzan was sitting defeated in the ground with a red-haired man standing with a sword in his hands and wearing the same earrings.
It was later explained in the manga that he gifted his earrings to his close friend, whose descendants are the Kamado family. The family treated these earrings as an heirloom for centuries.
4. His Twin Brother is Upper-Rank One
Yoriichi had an older twin brother, Michikatsu Tsugikuni. As a child, he was abused by his father, so it was Michikatsu who always helped him. However, he was not as talented as Yoriichi and slowly became jealous of his brother.
When Michikatsu realized that there was no way he can surpass Yoriichi, he decided to give it up altogether and become a demon.
He changed his name to Kokushibo and worked his way to the top demon among the Twelve Kizuki. Kokushibo is one of the oldest demons in the series. Even centuries after his transformation, he bears a striking resemblance to Yoriichi and still wields a sword in battle.
5. Yoriichi was the Only Being Feared by Muzan
Muzan is the strongest living character in the series. As the first demon who has been living for over a thousand years, his powers are unparalleled. He only has two weaknesses; direct sunlight and Sun Breathing Technique. Yoriichi Tsugikuni was able to defeat Muzan in a one-on-one fight, but couldn't kill him.
Muzan sustained serious injuries which never healed and kept burning him to this day. Muzan claimed that even though the world condemns him as a monster, the real monster was actually Yoriichi. Muzan's fear for Yoriichi Tsugikuni runs deep in his bones, making him want to kill Tanjiro just because the latter was wearing Yoriichi's earrings.
6. His Sword can Block the Healing Ability of a Demon
The reason that Muzan's injuries weren't healed wasn't because of the Sun Breathing Technique. Instead, it was due to the unique ability that his sword had. His sword can change color from black to crimson red.
Once it turns red, it can burn any demon and suppress its healing ability indefinitely. Yoriichi's sword is considered the strongest weapon and the series, making even the most powerful demon to be in burning pain for centuries.
7. Yoriichi Created the Thirteenth Form to Defeat Muzan
Only the twelve forms of the Sun Breathing Technique were passed down to the demon slayers. For generations, members of the Kamado family prayed to the sun god by performing a special dance continuously from sunset to sunrise at the start of each year.
However, Tanjiro learned later on that all the steps of the dance were created using the twelve forms of the Sun Breathing Technique. Yoriichi developed the thirteenth form that uses all the twelve forms continuously in succession to increase one’s speed and accuracy. This attack is the only way to kill Muzan since it hits all of Muzan's vital points.
8. He was the First Person to be Born with a Demon Slayer Mark
Yoriichi was born with the demon slayer mark, making his father believe that he was a devil. This led to Yoriichi's tragic childhood as he suffered his father's abuse. He is the only known character who was born with the mark. Unlike him, Tanjiro developed it later on and mistook it for a burned scar. Meanwhile, Giyuu and several other Hashiras trained relentlessly to awaken the demon slayer marks.
This is also the reason why he lived a long life compared to his peers. Those who awakened their marks all had a shorter life span than average. However, because he was born with it, he lived his life normally and had strength multiple times more than them.
9. He was Sick and Weak as a Child
Yoriichi had a very pale-looking appearance with a very weak body in his childhood. As a child, he was so sickly and weak that he wasn't even able to stand on his own. He didn’t say a word until he was seven years old, making everyone think that he was mute.
Yoriichi Tsugikuni was born with a mark that gave him the ability to see the bodies of living things in transparency. However, that very mark was considered demonic, making it the reason for his tragic childhood.
10. He Died at the Age of 85
When Yoriichi was 85, he met his brother who had turned into a demon. He cried in pity for Kokushibo, who had given up his humanity. Seeing a weak, old man pitying him, angered Kokushibo. Kokushibo tried to kill him, but the latter put up a good fight despite his old age.
He was able to slit Kokushibo's throat in an instant. After healing, when Kokushibo was planning to launch an attack, he saw Yoriichi standing still. He then realized that Yoriichi had died standing up because of his old age. Even as a demon, Kokushibo felt remorse for his death. Kokushibo realized that Yoriichi still kept the flute he had given him as a child. He took it back and always kept it with him as a memento.