Who Killed Tanjiro’s Family? Which Demon is it?

So I was rewatching Demon Slayer anime’s first season with a friend, and he was intrigued by how Tanjiro’s sense of smell linked Muzan with the Kamado family massacre.

As a manga reader, I knew the answer but let him ponder for some time. Why would the Demon King himself get down from his throne to kill a mere family out in the mountains?

It doesn’t make sense. Or does it? Well, consider this your spoiler warning.

Kibutsuji Muzan, the Demon King, killed Tanjiro Kamado’s family and turned his sister (Nezuko) into a demon. He visited their home in search of the “perfect demon host” that could rid Muzan of his Achilles heel: sunlight. Muzan massacred the Kamado family when he failed to accomplish his goal.

I know you have too many questions. Let’s continue.

1. Why the Kamado Family?

The fascinating and mysterious history associated with Tanjiro’s family, along with the unique abilities that Nezuko and Tanjiro display — makes it undeniable that their blood is special.

Hints relating to the Kamado family and their deaths have been dispersed throughout the story.

Tanjiro being a Breath of the Sun User, his sword’s color, the art of the Dance of the Fire God, and Nezuko’s ability to forsake human oriented diet and withstand the sun amounted to a greater truth.

It is no coincidence that Tanjiro’s ancestor was associated with the first Demon Slayer, Yoriichi, a Breath of the Sun User. Therefore, it can be ruled that the death of Tanjiro’s family was no mere killing — it was intentional.

While it was never explicitly revealed in the manga, I believe Muzan went to the mountains searching for Tanjiro. Because we later find out Tanjiro Kamado is the perfect host for the Demon King. 

2. Why Kibutsuji Muzan killed Tanjiro’s family?

Muzan’s history with Yoriichi is quite astounding. Muzan sees the Hanafuda earrings as a symbol of threat to his existence which he clings to. The Kamado family’s tradition of passing down Hanafuda earrings is no innocent factor.

Muzan’s encounter with Tanjiro showcased Muzan’s reaction to anyone associated with Yoriichi and the Breath of the Sun Users. 

The Kamado Family’s background is interlinked with the Breath of the Sun Users — enough to make the overly cautious Muzan kill them.

Muzan being the perpetrator, is supported by Tanjiro’s great sense of smell. Upon picking up Muzan’s scent, Tanjiro can quickly identify that his scent was present during the scene of the murder.

3. Why did he turn Nezuko into a Demon?

Muzan’s decision to make Nezuko a demon may have arisen from an experimental view — which has been fruitful. Nezuko can withstand the sun, something Kibutsuji has longed to achieve for centuries.

Tanjiro’s fate can simply be his luck and Muzan’s lack of awareness of the family’s size. But why was Nezuko made a demon? The answer is Kokushibo.

As we all know, Muzan searched for people who could withstand sunlight when they turned demon — the Perfect Demon.

Kokushibo managed to stay the Upper Moon Demon One for centuries – in this case, his abilities can be addressed in light of his family background, i.e., the Breath of the Sun Users.

4. Old Theory: Kokushibo’s Role

Before the revelation, another theory was going around a few months back. I think it is worth mentioning, so here it goes.

If not Muzan, the only contender would be the Upper Moon One, Kokushibo.

It was revealed that Kokushibo is the twin brother of Yoriichi. Someone so high up in Muzan’s army must have much of Muzan’s blood in his system.

Although this theory had several plot holes as to how Tanjiro didn’t pick up the rest of Kokushibo’s scent, along with no insight into Kokushibo’s motives.

5. About Demon Slayer: Kimetsu No Yaiba

Demon Slayer: Kimetsu no Yaiba is a Japanese manga series written and illustrated by Koyoharu Gotoge. Its publication in Shueisha’s Weekly Shonen Jump began in February 2016 and ended in May 2020 with 23 collected tankōbon volumes.

In a world filled with demons and demon slayers, Kimetsu no Yaiba follows the lives of two siblings Tanjiro and Nezuko Kamado after— the murder of their family at the hands of a demon. Their hardship does not end there, as Nezuko’s life is spared only for her to live as a demon.

As the oldest sibling, Tanjiro vows to protect and cure his sister. The story traces the bond of this brother-sister or better yet, demon slayer and demon combo against the odds of an arch antagonist and the society.