The Demons of Demon Slayer are immortal and (mostly) malevolent beings who serve as the main antagonists of the series. While all Demons share basic abilities and weaknesses, there are a wide variety of demons throughout Demon Slayer. As Tanjiro and his friends, Inosuke and Zenitsu, climb the ranks of the Demon Slayer Corps, they face an increasingly tough array of demons.
All demons in Demon Slayer possess immortality, regenerative abilities, flesh manipulation, and physical capabilities beyond that of humans. The consumption of humans allows demons to grow in strength and gather power. In Demon Slayer, Demons also possess unique abilities, known as Blood Demon Arts, which are spells they can cast due to the unique nature of their blood. These abilities combined create a vast array of demons throughout the Demon Slayer universe.
Demons' weaknesses tend to be relatively universal; fatal sunlight burns, being decapitated by Nichirin Blades, wisteria flowers, and the Curse of Kibutsuji affect all demons (barring a few exceptions). However, the fact that each demon has unique abilities means that Slayers must always adapt to defeat their enemies. Here's a guide to the biggest Demons of Demon Slayer season 1.
Nezuko Kamado
One of the main protagonists in Demon Slayer is Nezuko Kamado, Tanjiro's younger sister. After being turned into a demon during a massacre of their family, Tanjiro declares that he will find a way to restore Nezuko's humanity. Nezuko's bond with her brother is what separates her from most other demons. While demons typically lose their ties to their humanity, Nezuko has killed multiple demons for attempting to kill her brother (or any human, as she has been conditioned to see them as her family). Nezuko regenerates strength differently than most demons; instead of consuming humans, she is able to restore her power through sleep. She also has the ability to manipulate her size to suit her needs, such as shrinking to the size of a child to fit inside of her box to shield herself from sunlight.
Nezuko is incredibly strong in battle against Demon Slayer's other demons. Her demonic status has given her incredible physical strength; particularly in her kicks, with which she's knocked a demon's head clear off of his body. Her Blood Demon Art also allows her to ignite her own blood into pink, demonic flames that deal significant damage to other demons while leaving humans unharmed. In Demon Slayer season 2, Nezuko also displays unparalleled healing abilities on herself and humans.
Tamayo and Yushiro
Tamayo and Yushiro are two other demonic protagonists that Tanjiro and Nezuko meet in Asakusa, Tokyo early on in Demon Slayer season 1. After a chance encounter with Muzan Kibutsuji, the Slayers learn that Lady Tamayo and Yushiro also hope to take down Kibutsuji, the villainous leader of the demons. As a practiced doctor, Tamayo has altered both of their bodies to require minimal blood and has severed her own demonic connection to Demon Slayer's Muzan Kitbutsuji, which means his curse no longer affects her. She has also developed a method to create new Demons, a process she offers to terminal patients as an alternative to death; the first Demon she created was Yushiro. Because Yushiro was turned by Tamayo, he also has no connection to Kibutsuji. Upon discovering she had the ability to create demons, Tanjiro agreed to bring Tamayo samples of demonic blood and to allow her to study Nezuko in exchange for Tamayo developing a cure for Demonism. Like Nezuko, Tamayo and Yushiro don't consume humans in order to feed; instead, Tamayo purchases the blood they need from the impoverished in the city.
Tamayo and Yushiro's Blood Demon Arts played integral roles in the Susamaru and Yahaba battle during Demon Slayer season 1. Outside of her medicinal abilities, Tamayo is able to cast multiple spells using her own blood. Scent of Illusory Blood: Visual Dream creates a hallucination of flowers to hinder vision, while Magical Aroma of Daylight acts as a truth serum that forces the recipient to confess their lies. Yushiro's Blood Demon Art, Blindfold, grants him the ability to mask something's appearance (like Tamayo's clinic) or reveal something's presence (like Yahaba's magical ability Koketsu Arrows) using a paper talisman.
The Hand Demon
The Hand Demon was a ruthless demon Tanjiro encountered during Final Selection at the beginning of Demon Slayer season 1. The demon was captured by a young Sakonji Urokodaki, the retired Water Hashira and Tanjior's mentor, and trapped on Fujikasane Mountain to be used as an obstacle for Final Selection. Enraged, the Hand Demon vowed to kill as many of Urokodaki's trained apprentices as he could, consuming 13 before Demon Slayer's Tanjiro successfully beheads him. Consuming a high amount of humans made the demon well-versed in manipulating his flesh, creating armor with his own extra limbs. These extra limbs, plus thick neck muscles, caused multiple blades to break before he could be beheaded.
Susamaru and Yahaba
Susamaru and Yahaba were Demons sent by Muzan Kibutsuji to hunt down Tanjiro in Asakusa after he first encountered Tanjior in Demon Slayer season 1. Susamaru has a ferocious fighting style centered around the incredibly dense Temari balls that her Blood Demon Art allows her to conjure at will, which can reach a speed intense enough to decimate demonic limbs upon contact. Yahaba possesses two morphed eyes in the palms of his hands that guide his senses, allowing him to create Koketsu Arrows that can force a target in whatever direction the arrow is facing. Though Susamaru claimed to be one of the Twelve Kizuki - a group of Demon Slayer's strongest demons - the lack of a number imprinted on her eye after her death at the hands of Tamayo reveals this wasn't the case.
Kyogai (The Drum Demon)
After helping Tamayo and Yushiro defeat Susamaru and Yahaba, Tanjiro next encounters Kyogai, the Drum Demon, in a twisted mansion. Kyogai possesses 6 Tsuzumi Drums embedded in his body, and when the drums were played, they would have various effects on his surroundings inside of his mansion. The drums could rotate the room, teleport the mansion's occupants, and create a slash attack. Kyogai was a former Twelve Kizuki, but was demoted by Muzan for not being strong enough. Kyogai managed to trap multiple demons, civilians, and Demon Slayers (including Inosuke) within the maze of his Drum House in search of a "rare blood" which is said to give more power than any other. Though Kyogai was defeated by Tanjiro, it was a bittersweet moment, as the demon found something he'd never found in life; someone who found value in his drum playing and his writing, past passions from his human life.
The Spider "Family"
The Spider Family is a clan of demons encountered by Tanjiro, Zenitsu, and Inosuke on Natagumo Mountain during one of the final arcs of Demon Slayer season 1. The clan consisted of five members; the Mother, who could turn people into puppets with her webs, the Son, who can manipulate poison, the Daughter, who could manipulate silk, the Father Spider, who could metamorphose into a stronger form, and finally Rui, who is especially resistant to the Demon Slayers' Nichirin swords. Rui was the Lower Rank 5 of the Twelve Kizuki, and the demon who built the Spider "Family" using his own blood to strengthen the other members. Rui has similar web abilities as the rest of his family, and also had the power to change their appearances to match his own to create a "perfect family." Rui was enamored with Nezuko and Tanjiro's genuine sibling bond, something he never had with the "family." After the rest of the family was eliminated, Rui was beheaded by Giyu Tomioka, the current Water Hashira, in one of Demon Slayer season 1's most climactic moments.
Muzan Kibutsuji And The Twelve Kizuki
Muzan Kibutsuji is the original demon in Demon Slayer's setting and is also the strongest one in existence. He has physical, mental, and supernatural abilities that outweigh all other demons combined. Kibutsuji has the ability to create new demons with his blood, and the passing of his blood allows him to both increase the power of other demons, and to curse the receiving demon to be destroyed upon uttering his name - or whenever he desires. He also has the ability to shift his body into any form. Since this ability is unique to him, it is likely he is the one who turned Nezuko into a demon in one of the first Demon Slayer episodes.
The Twelve Kizuki are twelve powerful demons who share blood with Muzan and who serve him most closely. They are divided into the Upper Rank 6 and Lower Rank 6 - although after Rui's death, the remaining Lower Ranks were destroyed by Muzan after he deemed them too weak to be useful. Only Enmu, the Lower Rank 1, was allowed to survive with an injection of Muzan's blood and an order to kill the Hashira Rengoku and Tanjiro in the last episode of Demon Slayer season 1.
The Main Villain In Demon Slayer Season 1, Explained
Although Demon Slayer season 1 sees Tanjiro, his friends, and some upper-level members of the Demon Slayer Corps go up against a variety of different demons, Muzan Kibutsuji remains the primary antagonist of the series. Kibutsuji never fights Tanjiro directly but is responsible for many significant events, starting with the murder of Demon Slayer protagonist Tanjiro Kamado's entire family and Nezuko's demonic transformation. Kibutsuji's misdeeds build to the battle with Susamaru and Yahaba and culminate in Enmu's quest to destroy Rengoku and the young Demon Slayers. Demon Slayer season 1's finale sets up this quest, to be continued in the Mugen Train arc. Since Kibutsuji is the source of Demonism and the all-powerful leader of Demon Slayer's vast ranking of demons, Tanjiro will eventually have to face and defeat him in order to finish Demon Slayer's main conflict once and for all. Although this battle doesn't come in Demon Slayer season 1, it will have to happen by the series' eventual end.