8 Demon Slayer Facts So Dark They Make the Anime Harder to Watch

SPOILERS for Demon Slayer: Infinity Castle Part 2

Demon Slayer has become one of the most popular modern anime in recent years, with its latest installment, Infinity Castle Part One: Akaza’s Return, shattering box office records and industry expectations. As of now, it stands as the seventh highest-grossing movie of 2025.

The series is packed with action, jaw-dropping animation, and emotional storytelling, delivering tragic, humanizing backstories to both the heroes and many of the villains. Its story has understandably and rightfully carved out a place for itself in millions of viewers’ hearts around the world.

Given that Demon Slayer strongly resonates with its audience, every tragic detail and harsh reality hit fans hard on a deeply emotional level. However, some facts are much more difficult to swallow than others, making rewatching the series with these details in mind a true act of endurance.

Tanjiro Kamado Was Only 13 Years Old at the Beginning

Sometimes, it’s difficult to remember the fact that Tanjiro Kamado was only 13 years old when the series began. It is harder still to remember that he and Nezuko were the oldest of their siblings and sole survivors of the massacre that stole their family.

Barely a teenager, Tanjiro was forced to endure the unthinkable. After his life was violently upended in a single night, he had few other options other than to carry the responsibility of protecting his sister while training to take on monstrous demons on his own.

Many characters in Demon Slayer were forced to witness horrible tragedies in their youth, a fact that is haunting and heart-wrenching. What makes it more difficult to swallow is that many of these characters had to go through horrors alone in their formative years, robbing them of their childhood and innocence.

The Final Selection Is Child Sacrifice

The Final Selection in Demon Slayer is a seven-day survival exam that determines whether or not a candidate is suited to join the Demon Slayer Corps. While the exam is designed to determine the strength of the candidates, the act of trapping participants on a demon-infested mountain with no outside aid is far too harsh.

The Final Exam led to the death of countless individuals, including 13 of Sakonji Urokodaki’s disciples alone, including Sabito and Makomo, who trained alongside Giyu Tomioka. Many of these characters were children themselves, who had already experienced a life of hardship, only to tragically die because of the Demon Slayer’s ruthless exam.

What makes the Final Selection especially unsettling is how openly it’s accepted by the Demon Slayer Corps. While Ubuyashiki expresses grief for the fallen candidates, he continues to run the exam with no safeguards in place. The result is a loss of human life, something that the Demon Slayers usually try to prevent in any other scenario.

Obanai Iguro Was Raised in a Cell as a Sacrifice

Obanai Iguro’s backstory isn’t revealed until very late in the story, likely as a reflection of how guarded he is compared to other characters. However, when it is finally revealed, it’s immediately clear that his childhood was very intense and tragic, arguably more so than anyone else’s.

Obanai was born the first male in centuries to an all-female clan devoted to a serpent demon. From birth, he was kept in a cage and excessively fed with the intention of turning him into a sacrifice. He was terrorized by the demon nightly and was left scarred by his own family after they cut his mouth from corner to corner.

When he finally escaped, the demon was so furious that it killed nearly his entire clan, leaving Obanai with a deep sense of guilt. From then on, he fought and killed as many demons as possible in an attempt to feel worthy.

Sanemi Shinazugawa Was Forced To Kill His Own Mother

Sanemi Shinazugawa’s childhood was completely shattered in a single night. As the oldest of seven children, Sanemi was determined to look out for his family. However, when his mother was transformed into a demon and slaughtered most of her children, it was Sanemi who was forced to kill her to protect Genya, the sole survivor of the attack.

The traumatic event was made more tragic when Genya had accused him of murder, not realizing the truth of what had happened until years later, complicating and straining their relationship. Sanemi’s actions, Genya’s accusation, and the loss of his family led Sanemi to become harsh and abrasive toward others, hiding the fact that he carries a lifetime of grief and responsibility on his shoulders.

Gyutaro Had To Watch Daki Die Twice

Gyutaro’s life was full of trials, violence, and fighting for survival. He and his sister, Daki, who was known as Ume in her human life, were born into extreme poverty and abuse; however, Gyutaro had made it his mission to protect his sister while working as a debt collector.

While Gyutaro was away earning money, Ume had stabbed a samurai in the eye after he insulted her brother, leading to her being bound and burned alive in retaliation. By the time Gyutaro had returned, her body was completely charred, barely alive, and he was fatally wounded after being cornered.

When found by Doma, Gyutaro made the choice to become a demon; however, they were eventually killed together during the Entertainment District arc, where Gyutaro had to watch his little sister die right in front of him for a second time.

The Ubuyashiki Family Is Forced To Mature Quickly

The Ubuyashiki family had long lived under the dark shadow of inevitability cast by a curse tied to their bloodline. This curse ensures that all male heirs die before reaching the age of 30, robbing them of traditional childhoods, forcing them to mature quickly, and take on adult responsibilities, including running the Demon Slayer Corps.

The Ubuyashiki family had little other choice than to bear the burden of responsibility in the battle against Muzan. Kagaya Ubuyashiki was only 13 when he married Amane and had kids by the time he was 15. Then his son, Kiriya Ubuyashiki, took the mantle as head of the Ubuyashiki family and leader of the Demon Slayer Corps at only eight years old.

The Demon Slayer Mark Is Fatal

The Demon Slayer Mark is a mysterious mark that appears on exceptionally powerful Demon Slayers. Those who awaken it gain extraordinary strength, speed, and perception, but the cost is high and unavoidable. Everyone who activates the mark is fated to die by the time they turn 25 years old.

Every Demon Slayer who activated the mark, including Tanjiro, is fated to only live a short life.

While the Demon Slayer Mark offers a massive boost in power, often coming when the Slayer is already facing extreme, life-threatening conditions, its drawback of severely shortening their lifespan is like adding salt to a wound. Every Demon Slayer who activated the mark, including Tanjiro, is fated to only live a short life.

The Youngest Hashira Has the Most Brutal Death

Muichiro Tokito is the youngest Hashira in Demon Slayer at only 14 years old. His death in the Infinity Castle is known for its sheer brutality and the tragic fact that he was so young when he met his end. While facing Upper Moon One alongside Gyomei Himejima, Sanemi Shinazugawa, and Genya Shinazugawa, Muichiro sustains catastrophic injuries.

He loses limbs, is impaled, and ultimately sliced in half, and yet remains alive, continuing to fight with all his might until the very final moments. After a short life of tragedy, Muichiro is arguably the most deserving of surviving and living a full life after the Infinity Castle. Yet, he’s tragically destined to meet one of the worst fates in the series.