The main plot of Demon Slayer, like many other anime, starts off with the main character, Tanjiro Kamado, having a call-to-action moment. This moment is when he returns to his home in the woods after a trip to the village only to find his mother and all but one of his siblings dead, with his only surviving sister, Nezuko, being gravely injured. Tanjiro’s father had already died of disease before the show began. However, that leaves one question, who killed Tanjiro’s family?

After discovering the bodies of his family, the existence of demons and their hunters, the demon slayers, are revealed to Tanjiro as he encounters the demon slayer Giyu Tomioka who holds the rank of Water Hashira. Tanjiro then starts his journey, becoming a slayer so that he can protect people from the same fate his family had, as well as look for a way to make his sister, who was converted into a demon, human again.

Tanjiro’s training is long and gruelling but eventually, he is able to attend the Final Selection, a test used as an entrance exam to join the Demon Slayer Corps. After being one of the very few to survive the test, Tanjkiro becomes an official demon slayer and embarks on his quest to protect others from the pain he faced.

Who Killed Tanjiro’s Family?

(Spoilers from the Demon Slayer anime ahead!)

In the first few arcs of the series, the identity of the demon that killed Tanjiro’s family was a mystery. It is later revealed that it was none other than the series’ main antagonist, Muzan Kibutsuji.

Muzan Kibutsuji

At first, this might seem a bit weird, as Muzan doesn’t seem to be the type to go out of his way to commit violence without a prompt. He’s more of a cold and calculated planner than a violent bloodlust-fueled brute like Akaza.

Why Did Muzan Kill Tanjiro’s Family?

(Spoilers for the Demon Slayer Manga ahead!)

However, in the Demon Slayer manga Muzan reveals his motivation for attacking the Kamado family. It turns out that Muzan attacked the Kamado family and specifically turned Nezuko into a demon in an attempt to create a demon that would be able to withstand being in the sunlight. You see, for as powerful and experienced as Muzan is, he and every other demon in the series have a crucial weakness and it’s the light of the sun. Even a little sunlight is enough to cause a Demon to disintegrate, making it an even more dangerous weakness than being decapitated.

Fans early on in the manga’s run rumoured that Muzan attacked Tanjiro’s family because of their connection to Sun breathing, the first breathing style that all others are derived from, this is actually not the reason. When Muzan attacked the Kamados, he injected each of them with a massive amount of his blood in the hopes that it would produce a demon capable of withstanding the sun’s rays. Muzan’s end goal was that if that kind of demon was produced, he would be able to replicate this power in himself so that he could finally stop living in fear of the sun.

It’s unknown if Muzan was unaware of the Kamado’s connection to Sun breathing with the family’s connection to Yoruichi Tsugikuni, the demon slayer who invented breathing styles and nearly killed Muzan 500 years before the plot of the anime.