Although the name Michikatsu has been lost in history, and rather replaced with the Demon name Kokushibo, Michikatsu Tsukigini is the older twin brother of Yoriichi Tsukiguni and a major antagonist in the Anime series, Demon Slayer: Kimetsu No Yaiba.
After spending a better part of his life wishing he had his brother’s natural talent; driven by his envy and hatred towards his younger twin brother Yoriichi, Michikatsu metamorphosed from a demon slayer into a demon. After he was turned into a demon by Muzan Kibutsuji, he became the strongest upper-rank demon of the Twelve Kizuki—holding the title Upper-Rank One, and as a result, he turned out to be the arch enemy of his demon slayer twin younger brother, Yoriichi Tsugikuni.
If you are a curious fan who hasn’t really grasped the backstory of Kokushibo being a demon while his younger twin brother Yoriichi is a demon slayer, this article highlights the back story of this villain who used to be a human and a demon slayer named Michikatsu during the golden age of demon slayers. This was before he was turned into a demon in his quest to become better than his younger brother.
What is Yoriichi and His Twin Brother Michikatsu’s Back Story?
Twins were a bad omen when Yoriichi and his brother Michikatsu were born, and when their father noticed that Yoriichi had an odd birthmark on his forehead, he threatened to kill Yoriichi. Fearing that their father will carry out his threat, their mother, Akeno Tsugikuni, reached a decision. The decision was that Yoriichi would be sent to the temple and educated to become a priest once he turned 10 instead of being executed.
Yoriichi and Michikatsu had drastically different childhoods because Yoriichi was separated from his brother and raised in a three-tatami room isolated from the rest of the family. Michikatsu sneaked behind his father to see his brother Yoriichi because he felt sorry for him. To make his Younger twin feel better, Michikatsu presented Yoriichi with a handmade flute as a gift.
Michikatsu was about seven years old when Yoriichi observed him practicing sword strokes. Yoriichi began to speak at that point, startling Michikatsu because prior to that time, he was thought to be deaf.
However, his claim that he wanted to become a warrior like his brother was disregarded because he would be sent to the temple as soon as he turned ten. He, however, persisted in observing Michikatsu’s training, and one day, one of their father’s men offered to train Yoriichi.
Yoriichi was able to strike the man four times despite the fact that the man had just demonstrated a simple stance. Michikatsu, who had never struck out before, was perplexed and pleaded with his brother to reveal his secret. Yoriichi instead revealed his dislike for fighting and announced that he no longer wanted to become a samurai, much to Michikatsu’s dismay.
Yoriichi however mentioned that he took a deep breath prior to taking a stance and examined his bone alignment, muscle contraction, and blood flow. This may have been an early example of the Sun Breathing technique that Yoriichi would later adopt. Michikatsu also became aware during this conversation that Yoriichi saw the bodies of living things as translucent, which motivated him to pursue blade mastery with even more passion.
The more Michikatsu studied the sword, the more he felt jealous of his brother, whom he believed was wasting his inherent physical talent. Additionally, he was afraid that since their father was likely aware of Yoriichi’s enormous ability, their roles would be reversed, and he would be the one sent to the temple in Yoriichi’s stead.
Yoriichi was also aware of this as well because the night their mother finally passed away from her illness, he went to Michikatsu’s room to tell him the news and bid him farewell because he intended to depart for the temple before their father could appoint Yoriichi as the family’s new head of household.
Yoriichi thanked his brother for all his support as he cradled the flute that Michikatsu had earlier given him with affection. Michikatsu, on the other hand, was irate and remained silent as his brother left; wondering how Yoriichi could appreciate a flute that wasn’t even able to play in tune.
When Michikatsu read his mother’s diary after she passed away, it became clear that Yoriichi had planned ahead of time and was completely aware of their mother’s illness, including when she would pass away and the progression of her left side’s weakness. This made him even more envious of his brother.
Michikatsu began to dislike Yoriichi after realizing that his younger twin was not only physically talented but also intelligent. He wished for his brother’s death, and when he didn’t hear from him for a while, he thought Yoriichi had indeed died.
Ten years later, Michikatsu married the mother of his two children and became a samurai. But, one night, a Demon attacked his camp and left him as the only survivor.
Surprisingly, Yoriichi showed up and quickly killed the Demon. He also consoled Michikatsu for failing to save his subordinates. Michikatsu then left his family and trained to become a Demon Slayer with Yoriichi. But seeing Yoriichi soon made him filled up with envy and rage as Yoriichi had become an object of Michikatsu’s hatred.
During training, Michikatsu observed his younger twin brother make an unsuccessful attempt to pass along his own breathing technique to the other Demon Slayers. Nevertheless, he modified them to match their own power, resulting in the first Breathing Techniques. He practiced with a Wind Breathing user at that time, honing his sword techniques with them.
Eventually, Michikatsu awoke a Demon Slayer Mark and created the Moon Breathing, a Breathing technique adapted from the Sun Breathing. Despite Michikatsu’s success with the Moon Breathing technique, he was angered that it was not as powerful as Yoriichi’s Sun breathing technique.
As a Demon Slayer, Michikatsu often took pride in the originality of his generation, but he found his brother’s optimism annoying when he mentioned that they were the only ones practicing their special Breathing Styles, the Sun Breathing and the Moon Breathing.
Are Yoriichi and Michikatsu Twin Brothers?
Yoriichi and Michikatsu Tsugikuni are twin brothers. Michikatsu is the older twin, and Yoriichi is the younger twin. Yoriichi lived up to the age of 85 and died of old age, while Michikatsu died as the demon Kokushibo after Muichiro’s nichirin sword prevented him from regenerating.
Yoriichi’s Family Tree
Yoriichi Tsugikuni and his twin brother Michikatsu Tsugikuni were born to an unnamed father and their mother, Akeno Tsugikuni, during the Sengoku period, which is known as the Golden age of demon slayers.
Yoriichi got married to his wife Uta, and they were expecting a baby when a demon killed Uta and their unborn child. Before becoming a demon, Michikatsu, on the other hand, got married and had two children, whence his descendants Yuichiro Tokito and Muichiro Tokito were begotten.
Why and How Did Yoriichi’s Brother Become a Demon?
Michikatsu became the demon Kokushibo due to his inability to surpass his younger twin Yoriichi and also because he had activated the demon slayer mark, which, although heightened his abilities, meant that he would die at the age of 25.
Michikatsu was convinced to change into a demon by the demon Muzan Kibutsuji and to take the name Kokushibo out of his frustration at his inability to match his younger brother’s prowess as well his concern for the consequences of awakening the Demon Slayer Mark.
Because he was a user of the Breathing Style, it took him three days to completely transform into a demon. Thus, the original name Michikatsu Tsugikuni was erased from history, and he became Kokushibo and eventually rose to the rank of Upper-Rank One Demon of the Twelve Kizuki, where he remained for hundreds of years.