The third season of Kimetsu no Yaiba, aka Demon Slayer, premiered its finale today, and right afterward, it was announced that the show would definitely be returning for its fourth season. The finale ended with the slayers killing Hantengu, the Upper Moon Four, and now they need to train even harder to face off the remaining demons. But the question is, “Who are these demons, and where did they come from?” Also, who was the first demon, and why did he create all these monsters in the first place? The progenitor of demons on earth is called Kibutsuji Muzan, and today we take a look at how Kibutsuji became a demon in the Demon Slayer anime.
From the episode titled Cruelty, which kickstarts the journey of the young charcoal seller Tanjiro Kamado in pursuit of a cure for his sister Nezuko, we’ve known of the existence of an evil so great that it not only kills humans but also corrupts the human flesh. While returning from the town after selling charcoal, young Tanjiro found his home devastated, with all his siblings and his parents brutally slaughtered, while his only surviving sister, Nezuko, had been turned into a demon. This bloodbath, like countless other such massacres, was courtesy of Kibutsuji Muzan, a monster so ruthless and violent that he killed without remorse, regret, or reason. He killed to satisfy his hunger for human flesh, to create soldiers to add to his army of demons, or just because his urge to watch a man die tingled from time to time. The strongest of his army were his six generals, or “upper moons,” as he called them: Kokushibo, Douma, Akaza, Hantengu, Gyokko, and Daki. Under these six were six more moons, although they were called lower moons and were starkly weaker compared to the top 6. Interestingly, Muzan himself had created the Upper 6 using his own blood, which is why only 12 moons can change a human into a demon. However, why did the Muzans come into existence, and why did Muzan have to start on this diabolical path?
It was the Heian period when Kibutsuji Muzan was a young man in his 20s. He belonged to an important house and had caretakers and a dedicated doctor looking after him because he had a strange illness. His blood was such that he’d not survive for very long upon reaching his 20s, and the only doctor who prepared medicines for him could never earn Muzan’s faith. The man always hated the doctor and called him a fraud, but he had no choice other than to drink the tincture the doctor had prepared for him. However, unable to control his anger in the face of his continuing illness, Muzan stabbed the doctor in the head, killing him instantly. It was only afterward that he realized that the medicine had begun working after all, and Muzan could feel supernatural strength coursing through his veins. The downside of this was that he could no longer step into the sunlight, and this became a matter of embarrassment and shame for the self-aggrandizing man. Meanwhile, he began feeling pangs of hunger that could only be satisfied by human flesh, and as a result, he began wolfing down humans.
Soon, Muzan was declared a terror, and the emperor’s soldiers tried to stop the man who was wreaking havoc in the town. However, the arrows and spears of the soldiers proved useless against this demonic entity, as he massacred several soldiers in one swift motion before going his way. He’d learned from the doctor that his condition of not being able to step out in the sunlight could be treated only through blue spider lilies, but despite scouring every inch of Japan, Muzan hadn’t found the flowers blooming anywhere. Thus began his mission to create demons by injecting his own blood into the bodies of humans, with one goal in mind. Muzan wanted to create as many demons as possible because he’d hoped that one of them would be able to develop immunity against the sun, the natural enemy of demons, with Muzan being the first one to exist. However, none of the moons, despite being absolute killing machines that’d survived through centuries by massacring and murdering people in the thousands, could withstand the sun. Instead, they’d turn to ash at the first ray of sunlight, making darkness their only refuge. Meanwhile, the corps dedicated to destroying demons, headed by Kagaya Ubuyashiki, had managed to take down the Upper Moon Six, sending panic through Muzan’s home, the Infinity Castle.
Determined to take down the slayers and frustrated that he’d not found the blue spider lilies even after 1,000 years of searching, Muzan sent two Upper Moons to the village where the corps members had their swords forged. It was only after both of these demons had fallen that Muzan realized there was a demon, a little girl whom he’d mutated, who was able to stand under the sun and not be burned to a crisp. That’s all the motivation this demon king needed to pursue this little girl now, and he’d not give up till he was able to devour this demon. Only by devouring a demon can another demon gain the powers of the one it ate, so Muzan hoped to inherit the abilities of this little girl named Nezuko to find the power to withstand the sun. What he didn’t realize or take into consideration was that her brother was Tanjiro Kamado, the young boy who’d sworn to bring Muzan to justice for the unspeakable crimes he’s committed against humanity. Now that Muzan plans to seek out Nezuko and devour her, he’ll most certainly find Tanjiro in his way because the elder brother won’t fail to protect his sister a second time. Additionally, all the Hashiras have begun training further to be able to fight the remaining three Upper Moons, who are arguably the strongest ones. Thus, all the questions, including whether Muzan finds Nezuko or not, will be answered in the next season, titled “Hashira Training Arc.”