“No, Yoriichi, I just wanted to be you.”
What started with a sibling rivalry, with typical human jealousy and hidden brotherly love, ended with an unmatched duel between a former human and an undefeatable human. Yoriichi was the sun, the strongest and the undefeatable, while Kokushibo was equally strong, with his forte being the moon breathing with which he became an exemplary strong samurai.
Kokushibo's story portrays how jealousy and the vile nature of humans and their competitive thirsts always lead to damnation when it turns into an obsession. Kokushibo was the demon identity of the man Michikatsu Tsugikuni, Yoriichi's brother, favoured by their parents. Despite the differential treatments that both these brothers received, there was strong love between the two. Michikatsu gifted Yoriichi a flute when they were young before Yoriichi left home to make his own life away from the temple, where he was sent to grow due to his illness.
« Michikatsu|Kokushibo didn’t care about Yoriichi and was never a good person,whether demon or human »— 煉獄🌸 (@washoi__washoi) July 4, 2020
He was and Yoriichi was the person he respected the most and he was jealous about the love he had by his mother,also bc Yoriichi was the only one who know his mother's illness* pic.twitter.com/hdhURETEg6
Once Mmichikatsu found out that their parents favoured yoriichi and wanted him to become the next head of the family despite Michikatsu being older than him, that was the start of Michikatsu harbouring unconditional jealousy and competitiveness to surpass Yoriichi in every way. Having the difference in their abilities and the supreme perfection in Yoriichi's abilities as a swordsman ignited the fire of jealousy and rage inside Michikatsu.
If he could not become the strongest demon slayer and a human, he set on to become the strong demon ever among the others, which placed him as the first upper rank among the twelve kizukis. He is also the ancestor of Muichiro Tokito and Yuichiro Tokito. He is the only one responsible for turning Zenitsu's senior into one of the twelve kizuki demons.
Characteristic of Kokushibo as a demon
He developed an extremely reserved persona with a disciplined demeanour as a demon. His unwavering loyalty towards Muzan showed his compliance to his duties as an upper-rank demon. He hardly conversed with the others and was harsh when anything did not match his liking leading to his rude and stringent persona as a demon. He was devoted to following every rule, not wavering a little. His dominating and strict presence always demanded obedience without any counterquestions.
The moon against the sun
In his last duel with his brother, he saw him die in front of his eyes without him being able to defeat him. After discovering that Yoriichi still treasured the handmade flute that he gave to him when they were young, he shed genuine tears. Despite the envy, jealousy, and hatred over abilities, Kokushibo deeply cared for his brother and kept the flute with him as a souvenir.
Kokushibo's bloodthirst and deepest desire were only to be known as the strongest. He honed his skills to the extent even chose to be an immortal and a fearful demon if it meant he would train himself to be the most talented and strongest demon among the twelve kizukis. He feared defeat to the extent that he lacked the human understanding of accepting loss and failure.
This immense self-obsession and an obsession for strength made him choose to be a demon, even when he wasn't satisfied when he was duelling against the hashiras. He only ever wanted to be the most muscular man he knew, and despite his hatred towards him, he wanted to be like him.
When he says that he wanted to be like yoriichi, the fatal flaw of human behaviour to be obsessed with perfection in strength is expressed very tearfully. The makers of Demon Slayer carved the entire story of Kokushibo to have the readers and the viewers feel sympathetic towards him, towards his efforts, and his misunderstanding of himself and his potential.
The fatal flaw of humans
Humans' obsessive, ambitious nature makes them turn into monsters who become power-hungry and will destroy everything. The demons signify another facet of human nature that the creators have promptly showcased for visual aids. His death was the most sorrowful part of his tenure.
Despite attaining immortality and immense power so much to become the top-ranked upper moon demon, he died with regrets and sorrow because he wanted to be the most remarkable human samurai with excellent skills and strength rather than turning into a slaughtering demon that kills people and derives power from the cannibalistic nature of the demons.
Kokushibo against the strongest hashira of the Taisho era
He was still undefeatable during the face-off with Sanemi, Muichiro, and Gyomei, with his excellent skills and deadly swordsmanship. His ultimate demise was brought upon by himself when he started to realise he lost his worth as a living being when he became a demon and could achieve nothing. He stopped regenerating and let the hashiras defeat him along with the sun, which was the only way to defeat demons.
The human-demonic binary
His swordsman skills were unmatched, along with his discipline and commitment to time. Each of these attributes made him a perfect samurai. His love for his brother remained unfazed even with the extreme jealousy and hatred. Kokushibo, as a demon, is the most respectful demon, as he was evil with unmatched atrocity and undefeated by everyone except his fate and understanding, which made him the perfect demon.
Like Satan, he was the fallen angel from the thesis world where everything followed the ideal of goodness. Being the moon, he reverted to the darkness and shone brighter even in the dark. His adapting moon breathing, opposite to his brother who created Sun breathing, speaks of the two extreme sides of the same pole that defined these brothers.