Warning: Contains major spoilers for Demon Slayer's anime AND mangaLike its predecessors such as Naruto and Bleach, Demon Slayer features some of the darkest moments in shonen anime. A world where demons lurk in the shadows of Japan, ready to torture and devour the humans who live completely oblivious to their existence, is horrific in and of itself. The rest of the show more than delivers on its bleak premise with many heartbreaking deaths.
Tragic origins notwithstanding, demons are cruel and powerful creatures. At best, they don’t care about the pain they cause their prey; at worst, they go out of their way to make the humans at their mercy suffer. And with someone like Kibutsuji Muzan in command, they’re no kinder to their fellow demons. All of this results in Demon Slayer being one of the darkest shonen series in recent memory.
10 Kamado Family Massacre
Audiences find out exactly what they’re in for with this show in the very first episode of Demon Slayer, aptly titled "Cruelty." Tanjiro lives a humble but happy life in the mountains with his mother and five younger siblings. Then one day he comes home to find them all slaughtered save for one. His sister Nezuko has been turned into a demon in one of anime’s most shocking episode one twists. The sight of a newly feral and starving Nezuko pouncing on her own horrified, confused brother fully intending to tear his throat out with her teeth is disturbing. As if Tanjiro wasn’t having a bad enough day, he is forced to think quickly to plead with Giyu for his sister’s life while still fending her off.
9 Susamaru’s Death
It was clear enough what a monster Muzan is from the carnage at the Kamado house alone. But the harsh rules he restrains his forces with show that even the lives of his own kind — his own creations — mean nothing to him. Tanjiro and Nezuko witness it firsthand when Susamaru accidentally says Muzan’s name after being defeated.
Susamaru instantly realizes she’s slipped up and begs for forgiveness, insisting that she would never reveal her master’s secrets. True as it might be, it doesn’t matter: Muzan’s curse kicks in and kills her horrifically from the inside out. And it isn’t just a simple kill switch: it’s intended as a cruel punishment for slipping up, bloody and gory as any battle, and despite having just been fighting for their lives against the demon, the Kamado siblings are appalled.
8 Mount Natagumo Arc
There are stronger demons in Muzan’s pocket than the Spider Family, but few are more iconic to the show as a whole. Mount Natagumo is their domain, and watching them pick off the Demon Slayer Corps trying to hunt them through the forest is straight out of a monster movie. Each of them is uniquely frightening, with the body parts and abilities of spiders given in some of the scariest transformations in anime.
Rui is the strongest and scariest, coldly torturing and killing his “family” and his enemies alike, but the powers he grants are no joke either. Father is a hulking monster with spider fangs and crushing strength, and the siblings transform humans into mindless spiders and melt them in cocoons. Tanjiro and company are way out of their depth until Giyuu and Shinobu show up.
7 A Ruined Happy Ending
The Mugen Train arc is a harrowing battle not just for Tanjiro, Zenitsu, and Inosuke, but even for Rengoku, the Flame Hashira. After fighting their hardest and breaking free of the most tantalizing dreams, they manage to kill the Lower Rank demon Enmu, and despite being exhausted, they rejoice in a mission with zero casualties. Then Upper Rank Akaza shows up.
Akaza immediately demonstrates the difference between the Upper and Lower Ranks of Muzan’s Twelve Kizuki. Kyojuro gives him an incredible fight, one that even impresses the characteristically arrogant demon, but ultimately succumbs to his injuries. The only thing saving the younger three is Akaza fleeing before the sun, leaving them to mourn over one of the Demon Slayer.
6 Entertainment District Final Battle
Two of the things that Demon Slayer does best are grueling fights and tragic backstory flashbacks. These two things come together beautifully and horribly in the Entertainment District Arc, with the reveal of the demon siblings Daki and Gyutaro. Made angry and cruel by a childhood of abuse, they take joy in torturing and killing anyone who crosses them.
Their fight with the Kamado siblings destroys the titular district and pushes all four of them to their absolute limits. Nezuko in particular loses control and not only beats Daki senseless but tries to eat the wounded humans caught in the crossfire. Daki, being no slouch herself, tears Nezuko quite literally limb from limb and pushes Tanjiro into deeper rage than viewers have ever seen him before.
5 Muichirou’s Past
Many Demon Slayers got into the job because they lost loved ones to demon attacks, just like Tanjiro. However, the Tokito family’s fate may be the most gruesome of all. The orphaned twins, Muichirou and Yuichirou, are attacked by demons, and Muichirou watches his stronger brother bleed to death while pleading for Muichirou’s life.
Muichirou barely survives after being stuck on the floor covered in maggots and insects for days. He’s so deeply traumatized that his brain blocks out the memories of what happened, and he subconsciously replaces his own personality with his brother’s as a survival mechanism. Muichirou’s young age and the fact that he forces himself through still more pain in training to get stronger make his background particularly dark.
4 Sanemi And Genya’s Past
Both Sanemi and Genya act cruel and aggressive toward Tanjiro. However, it’s revealed that the three have more in common than they thought. As kids, Sanemi and Genya were the oldest sons of a large family, who swore to protect their mother and siblings after their abusive father died. But they could never have prepared for a demon attack, let alone from their own transformed mother.
Genya, realizing that something’s wrong and trying in vain to stop his siblings from opening the door, is almost more terrifying than Mama Shinazugawa tearing in and slaughtering most of her children. Worse, Sanemi kills the demon and saves Genya, but Genya doesn’t realize the demon and their mother were one and the same. Because of the misunderstanding, the brothers are estranged, their relationship defined by grief, regret, and desperation rather than the love and closeness the Kamado siblings enjoy.
3 Obanai’s Past
Most victims of demons don’t die quickly, and the Serpent Hashira’s childhood may be one of the most tragic backstories in any anime. The Iguro clan worshiped a snake demon that loved to eat children, and Obanai was raised in a prison cell as an intended sacrifice. The demon’s “affection” for him took the form of having his mouth slit open and stalking him at night, to his constant terror.
Escaping saved his life and caused him even more trauma at the same time. The demon killed the entire clan in outrage, and Obanai’s one surviving cousin blamed him for not letting himself be eaten. As an adult, he knows that what his family did was wrong, but still struggles with self-loathing and guilt over his upbringing and their deaths, and believes he can only redeem himself through death.
2 Doma
Just Doma. Every single moment the Upper Rank Number Two is on page or screen, something horrible is happening: both in the story proper and in flashbacks to tragic backstories. As a human child, Doma was the subject of a cult that cheated people out of their belongings and witnessed the murder-suicide of his parents, shaping his treatment of others as an adult demon.
Doma personally devoured both Inosuke’s mother and Shinobu and Kanao’s sister. He maintains his cult as a demon, considering it a help and an honor to be either transformed or eaten by him. Even the satisfaction of the Kochou sisters’ victory over him is weakened by the fact that he simply doesn’t care that he’s dying: life means that little to him, his own included.
1 Tanjiro’s Transformation
Anime heroes who become villains are some of the most shocking transformations to witness: even worse if it’s happening against the hero’s will. To spite the humans who finally defeated him, Muzan forces his will into Tanjiro, transforming him into a demon. Watching Tanjiro’s eyes burn red and his smile disappear into a snarl is one of the manga’s most shocking images.
While willing to kill, Tanjiro always fights to protect others and to give demons a peaceful end by his sword. His corruption after being a perpetual beacon of hope and after the deaths of so many Demon Slayers is the series’ darkest hour. Strong as he is, he can’t repress Muzan on his own: it’s the power of his loved ones coming together to protect him that turns dark to light and destroys Muzan for good.
A story as optimistic as Demon Slayer can't fully get its message across without considerable darkness to contrast it. Horrific transformations, abusive childhoods, and demon slaughter are the stuff of nightmares, constituting the very darkest moments in Demon Slayer.
