One of the most interesting plot points of Demon Slayer is that Muzan Kibutsuji is the original and progenitor of all demons. While there are confirmed instances of demons other than Muzan turning humans, it all starts with Muzan and his initial transformation.
One of fans' biggest questions in Demon Slayer is, why did Muzan turn Nezuko into a demon? Both the specific and general answer to that lie in Muzan’s backstory and his ultimate goal for demon-kind.
This article will explore why Muzan turned Nezuko into a demon in Demon Slayer.
WARNING: HEAVY DEMON SLAYER ANIME AND MANGA SPOILERS BELOW
Demon Slayer fans frequently ask why Muzan turned Nezuko into a demon
Even as far as humans go, Muzan Kibutsuji was very frail. When born, he was considered stillborn as he didn’t cry at all until he was about to be cremated. Muzan’s heart also stopped several times in his mother’s womb. In his younger years, Muzan was diagnosed with a disease that would kill him by the time he reached 20 years of age.
Muzan received a prototype medicine from a doctor, but killed the doctor as a result of being enraged by his worsening condition. Tragically, Muzan realized shortly after that the prototype medicine was working. Muzan’s body was much stronger, and Muzan was unphased by his new need to consume human flesh.
Muzan’s main concern was his new inability to walk into the sunlight. This would eventually set up his motivation for the next several hundred years, as all Muzan wanted was to walk in the sun again. To this end, Muzan created hundreds of demons over the years in the hopes they’d find the final piece of the medicine or discover a way to walk in the sun.
Thus, Muzan created demons for hundreds of years even when he didn’t want to turn someone. Since he didn’t know anything about the Blue Spider Lily medicine, he needed others to find the plant for him by happenstance. This is the general reason why Muzan turned Nezuko into a demon.
More specifically though, was the fact that Nezuko was of Kamado blood. Kokushibo and Muzan both eliminated every Demon Slayer who practiced Sun Breathing after the legendary Demon Slayer Yoriichi nearly killed Muzan. The two thought they had eliminated them all, but the Kamado family knew the style as the Hinokami Kagura dance.
Being a family loved by the sun and by Sun Breathing, Muzan’s encounter with them was quite beneficial indeed. Muzan finally had a family to turn to which was so loved by the sun, and had many members born with the Demon Slayer mark. As a result, Muzan tried to turn every member of the Kamado family present that day, but left the spot thinking none were a success. Little did he know, Nezuko Kamado survived and eventually turned.
In addition, Nezuko does eventually become a demon capable of withstanding the sunlight. While Muzan’s original goal was to find the Blue Spider Lily plant and complete its medicine, creating a demon capable of withstanding the sun also achieves the same end.
While Muzan created nearly every demon with the general goal of finding the Blue Spider Lily or finding a way to stand in the sun, the Kamado family was different. Having had several members of the family born with the Demon Slayer mark, Muzan was sure the Kamado family was loved enough by the sun to withstand it as demons.
As a result, Muzan tried turning every Kamado family member present that day into demons who could hopefully, eventually, withstand the sun. While Muzan was correct in thinking most of the family had died from his blood’s poison, Nezuko did end up surviving.
As a result, through Nezuko’s journeys and constant editing of her blood, she was eventually able to become the first demon in Demon Slayer capable of standing in the sun.