Demon Slayer: Here's Why Muzan Killed Tanjiro's Family (2025)

Demon Slayer: Kimetsu no Yaiba started off the way any great story does: with the brutal slaughter of an entire family composed mostly of children. When Tanjiro Kamado returned home to find most of his family dead and his sister Nezuko turned into a demon, he made it his life's mission to track down the demon responsible.

A couple of years later, after Tanjiro had joined the Demon Slayer Corps, he encountered Muzan Kibutsuji while visiting the city of Asakusa. It was there that Tanjiro confirmed by Muzan's scent that he was the demon who'd massacred the Kamado family. Throughout the series, fans learn that most demons habitually slaughter people, including families. But why did the Original, the Progenitor, and the King of Demons decide to butcher some random family living alone in the mountains?

Updated on August 7, 2024, by Ajay Aravind: Muzan's appearance in the final episode of Season 4 was quite unexpected, as was the resulting attack planned by Kagaya Ubuyashiki, Tamayo, and Gyomei Himejima. Now that everyone has been transported to the final destination — the so-called Infinity Castle — fans are excited to see how Tanjiro is going to take down the Demon King. As such, we've updated this article with some more information about Muzan's mysterious motivations.

Demon Slayer's Muzan Kibutsuji Has a Major Weakness

The Demon King Cannot Walk in the Sunlight

Muzan Kibutsuji, despite being an evil demon who's lived 1,000 years and murdered thousands of people along the way, has a pretty relatable motivation: he doesn't want to die. Muzan was dying of an incurable illness when a doctor in Japan's Heian era used the mysterious Blue Spider Lily and accidentally turned the ailing Muzan into the first demon. However, Muzan quickly realized that although he had gained incredible powers, he would die if he was exposed to sunlight. Muzan found it humiliating to have to stay indoors during the day and spent the rest of his prolonged life searching for a way to become the perfect being immune to death.

Other than the sun, Muzan's biggest fear is Sun Breathing, the original and most powerful Breathing Style used by Demon Slayers to battle demons. Yoriichi Tsugikuni, the first swordsman to ever use Breathing Styles, once nearly killed Muzan with Sun Breathing — and Muzan has been both physically and psychologically scarred ever since. As such, Muzan went to great lengths to ensure Sun Breathing was wiped out. Partnering with Kokushibo, the Upper Rank One of the Twelve Kizuki and the brother of Yoriichi, Muzan traveled around Japan, killing anyone who'd even heard of Sun Breathing. The only people they missed were the ancestors of the very same family Muzan would slaughter at the beginning of Demon Slayer: the Kamados.

Why Did Muzan Kill Tanjiro's Family?

He Wanted to Create a Demon Immune to Sunlight

Members of the Kamado Family in Relation to Tanjiro:

• Tanjuro (father)
• Kie (mother)
• Nezuko (sister)
• Rokuta (brother)
• Hanako (sister)
• Takeo (brother)
• Shigeru (brother)

For a while, it was suspected by fans that the reason that Muzan had killed Tanjiro's family was that he'd somehow learned that they had been passing down Sun Breathing as the Hinokami Kagura. It was fortunate for Muzan that Tanjuro Kamado, Tanjiro and Nezuko's father, had already passed away because Tanjuro was a true master of the Hinokami Kagura. However, a flashback from Nezuko's POV regarding the attack in the manga's final arc, "Sunrise Countdown," confirmed that Muzan's motivation for massacring the Kamado family was unrelated to Sun Breathing, and ultimately a successful ploy.

Muzan Kibutsuji hates demons despite having created each and every one of them. As it turned out, the only reason Muzan kept creating demons even though he didn't want to was in the hope that one of them would develop the ability to withstand sunlight. When Muzan killed Tanjiro's family, he injected each of them with a massive dose of his blood, hoping that the sheer power they'd get from him would birth a demon capable of walking in the sun.

Demon Slayer's manga never confirmed why Muzan chose the Kamados specifically, so perhaps it was a two-birds-one-stone situation with the elimination of Sun Breathing. Maybe he just assumed no one would notice if the Kamados disappeared, considering his preference for keeping a low profile anyway. By creating a demon who could survive exposure to the sun, Muzan would then only need to consume that demon to gain the ability for himself.

The Demon King's Dream Was Fulfilled by Nezuko

Nezuko Becomes Immune to Sunlight in the Swordsmith Village Arc

In Season 3's Swordsmith Village arc, Tanjiro and Nezuko are fighting the Upper Moon 4 Hantengu. With Genya and Mitsuri also battling Hantengu's many forms, Tanjiro goes on the hunt for the demon's original body. Just before he can catch and kill Hantengu, the sun begins to rise. Nezuko immediately begins experiencing extreme burns on her body, forcing Tanjiro to ignore Hantengu and protect her. However, Nezuko kicks him away, effectively ordering him to finish the Upper Moon 4.

Despite the sun causing even more damage, Tanjiro accepts her decision and eventually kills Hantengu. He consequently breaks down in tears, believing that his sister had been killed by the rising sun. To everybody's surprise, a completely unharmed Nezuko appears before him. She even speaks for the first time, proving that she is now immune to sunlight as well as growing stronger. Meanwhile, Muzan basks in the delight of having found a demon who can resist the sun, because it means that he can now fulfill his greatest desire.

Muzan's Decision to Kill the Kamados Ultimately Backfired

Tanjiro Joined the Demon Slayer Corps to End Muzan

Notable Demon Slayers in the Final Battle against Muzan:

• Giyu Tomioka (The Water Hashira)
• Sanemi Shinazugawa (The Wind Hashira)
• Gyomei Himejima (The Stone Hashira)
• Mitsuri Kanroji (The Love Hashira)
• Obanai Iguro (The Serpent Hashira)
• Muichiro Tokito (The Mist Hashira)
• Zenitsu Agatsuma
• Tanjiro Kamado
• Nezuko Kamado
• Inosuke Hashibira
• Shinobu Kocho (The Insect Hashira)
• Kanao Tsuyuri

The Demon Slayer Corps had been established by the Ubuyashiki with the singular goal of eradicating Muzan. They struggled for hundreds of years, killing scores of overpowered minions, but none of them even managed to land a scratch on the Demon King after Yoriichi Tsugikuni. Unfortunately for Muzan, his decision to massacre the Kamados would lead to his ultimate destruction. Although Nezuko's immunity to sunlight demonstrated that he had made the right choice, Tanjiro's vengeance and protectiveness would prevent Nezuko from being eaten by Muzan.

In fact, Tanjiro only took up Water Breathing in order to keep Nezuko safe. It was only after learning about Muzan's role in his family's death that he decided to join the Demon Slayer Corps. He becomes stronger and stronger throughout Demon Slayer, even unlocking the secret of Hinokami Kagura that terrifies Muzan. As of the end of the Hashira Training arc, however, Muzan managed to escape Ubuyashiki's genius strategy by exploiting Nakime's teleportation ability. Now that all the demon slayers have been transported to the Infinity Castle, the real battle can begin.

Demon Slayer

TV-MA

Animation

Action

Adventure

Fantasy

When Tanjiro Kamado returns home to find his family was attacked and killed by demons, he discovers his younger sister Nezuko was the only survivor. As Nezuko slowly becomes a demon, Tanjiro sets out to find a cure for her and become a demon slayer so he can avenge his family.

Release Date

April 6, 2019

Cast

Zach Aguilar , Abby Trott , Aleks Le , Bryce Papenbrook , Brianna Knickerbocker , Zeno Robinson , Johnny Yong Bosch , Erika Harlacher , Ray Chase , Kira Buckland

Studio

Creator

Streaming Service(s)

Crunchyroll