During episode three, we learned that the Yoriichi Type Zero was built by Kontetsu's ancestors more than 300 years ago during the Sengoku era.
This is the sword that appeared out of the neck of the doll at the end of Demon Slayer season three's second episode. In the manga Tanjiro has the sword repaired by Haganezuka, who he initially traveled to the Swordsmith Village to find.
As the battle reached its climax, Tanjiro was able to knock the doll's head off and discovered that the mechanical body contained a mysterious sword. Fans of the manga will recognize this sword as the one carried by Yoriichi Tsugikuni himself.
Now armed with his new ability, Tanjiro lands his first blow on Yoriichi Type Zero, though it was nothing more than a nick on its legs. The hidden katana in the doll.
Toho Co., Ltd. Black is the most mysterious color of all the blades, and is held by the main character, Tanjiro. It is a rare blade and represents the sun; it also holds a theory that the demon slayers who own this sword are not to live a long life.
Of course, the one who takes the top spot in terms of the best swords in Demon Slayer is Tanjiro's black Nichirin blade.
Yoriichi Tsugikuni is a Demon Slayer from 300 years ago, and the inspiration for Kotetsu's training doll.
Combat Style
"Breath of the Sun: Thirteenth Style") is the thirteenth form the Sun Breathing and the pinnacle of all Breathing techniques in history. This technique was created by Yoriichi Tsugikuni himself in order defeat Muzan Kibutsuji.
Demon Slayer season three spoilers follow.
We watched Tanjiro spend most of the episode battling against an extremely cool mechanical doll, the Yoriichi Type Zero, under the tutelage of young swordswmith Kotetsu until the pair were surprised by a treasure hidden inside.
Some of the characters who have faced Yoriichi and survived
This happened due to a treatment that had gone wrong. While he was being treated, Muzan killed the doctor because he was not able to observe any results.
After Tanjiro chipped his sword in his battle against Upper Rank Six, Hotaru trained more to make a stronger sword. Hotaru demonstrated his professionalism and expertise when he polished and sharpened the 300-year-old blade left in Yoriichi Type Zero while completely ignoring the wounds he received from Gyokko.
Since the mechanical doll was based off Yoriichi Tsugikuni, it had to be given six arms to recreate his swordsmanship style, the doll was also able to execute 108 various moves and is said to be stronger than an average human.
Tengen is one of the only known Demon Slayer and Hashira to retire due to being permanently disabled instead of death or age, the other being Jigoro Kuwajima. He and Inosuke Hashibira are the only known Demon Slayers who use two Nichirin Swords instead of one.
Yoriichi Tsugikuni is the creator of the Sun Breathing style and is also the strongest demon slayer that has ever lived. He existed nearly 500 years prior to the events of Demon Slayer and struck fear into the hearts of every demon he came across.
1 Yoriichi Tsugikuni
Yoriichi was the very first user of the Breathing Styles and he came up with Sun Breathing, a powerful breathing form that is known to be the most effective against demons.
The Thirteenth Form of the Sun Breathing Style is unique in the sense that it doesn't really have a name of its own. Rather, it's a combination of all the twelve forms present in this style, used in succession to maximize their power. This move was devised by Tanjiro solely to defeat Muzan.
Only two Slayers were ever known to be older than 25 with a Mark. Yoriichi lived till old age, likely due to him having been born with the mark and thereby avoiding the curse altogether. Gyomei on the other hand did not activate his Mark until he was already older than 25.
Unlike all other marks users in his era, Yoriichi was able to defy fate and lived to about 85 years of age (the average life expectancy during the era Yoriichi was presumed to have been born was between 30 ~ 50 years).
In the Demon Slayer manga's final chapter, Yoriichi and his family have been reincarnated and are seen in the deep background of a panel as Tanjiro's own descendants head to school.
Also, black is frequently perceived as the absorption of all colors, which might mean that Tanjirou is set to navigate through sword colors and Breathing – which is demon slayer technique that allows them to hone in the power that they hold within themselves to the sword.
Tanjiro Kamado wields a black Nichirin blade, but the symbolism of such a sword was initially unknown. Black blades are seen as a rarity, as demon slayers who wield them are doomed to die young. No wielder of a black sword has ever become a Hashira, either. However, this is all superstition.
Being one of the strongest Hashira, Sanemi's sword matches his appearance. His sword is very durable and lasts throughout the series. It had no problem piercing through the box that Nezuko is held in. He fought against Kokushibo during the final arc of the manga.