|“||I want to die defeating Muzan, and I pray that it will purify my filthy blood. Then, if I am reborn as a human being in a peaceful world without Demons, I will tell you of my feelings for you.||”|
Obanai is a young man of short stature and a pale complexion. He has straight-edged black hair of varying lengths, the longest reaching down to his shoulders and the shortest stopping at his cheekbones, which he wears down with two shorter strands hanging between his eyes. His eyes are almond-shaped and tilt upwards on the far sides, and are unusual due to Obanai possessing heterochromia—his right eye is yellow and his left eye is turquoise. Obanai's mouth is also unusual in that, when he was twelve, it was cut from its corners to his ears to make it appear more like that of a snake, leaving a large wound that he keeps hidden under the bandage he wears over his lower face.
He wears a navy blue version of the standard Demon Slayer uniform, along with a black and white pinstriped haori, the hem and cuffs of which are striped lengthways rather than vertically, which covers his hands. Obanai also sports bandages in place of the leg-wraps around his calves, as well as another set of bandages that cover his mouth, and blue-strapped zori on his feet. He is also always seen with his white snake, Kaburamaru, wrapped around his shoulders.
When he was a child, Obanai had waist-length hair that he wore tied down his back with a long white bandage and a regular-looking mouth. He wore a plain white kimono.
Obanai is a very harsh and strict individual who shows no concern for those who do not abide the Demon Slayer conduct. His expectations for his fellow Demon Slayers are nigh-unrealistic, berating Tengen Uzui for suffering heavy wounds against the "weakest" Upper Moon and telling him to "fight to the death" when Tengen insists on retiring. In reality, the Demon Slayer Corps had gone 113 years without killing an Upper Moon, and Shinobu Kocho later estimates that each Upper Moon is equal to three Pillars in strength.
Obanai's devotion to the future of the Demon Slayer Corps comes close to being at others' expense, such as when he tries to force Tengen to stay with the Demon Slayers even after losing an eye and arm, and when he ties up lower-ranked Demon Slayers and uses them as obstacles during Pillar Training for relatively petty reasons. He also sees the newer Demon Slayer recruits as weak and incapable of improvement, expressing surprise when Tengen informs him that Tanjiro Kamado survived the mission.
Despite his merciless personality, there are two people he cares deeply about: Kagaya Ubuyashiki and Mitsuri Kanroji. He has a crush on Mitsuri, which is implied by most of their companions save for Tanjiro and Mitsuri herself; even giving her her green socks she wears as a present. He threatens Tanjiro for growing too close to her (for his tastes) and he is the first person to meet up with her in the Dimensional Infinity Fortress.
Obanai is also noted to possess an immense sense of self-loathing due to the fact that he was born to a selfish and immoral clan who would mercilessly sacrifice to a Demon for their own monetary gain. Obanai considers himself and his family to be so tainted that, in order for him to ever be worthy of Mitsuri, he would first have to die and reincarnate into a whole new being life before confessing his feelings to her.
Obanai was born into a clan of thieves who lived off an excessive amount of riches that had been stolen from those who had been killed by the Demon that they worshipped. This Demon took the form of a woman with a snake-like lower body and face, and had a great taste for newborn babies, which is what the family sacrificed to her in exchange for their riches.
As the first boy born into the family for 370 years, Obanai lived out all of his days locked in a wooden cage being spoiled by his family, who insisted on bringing him so many plates of rich food that he became sick of it. The Snake Demon also took a liking to Obanai, since he was a rare male child with multicolored eyes, and would spend the nights slithering around his cage in the dark and staring at him, which frighted Obanai so much that he couldn't sleep.
When he turned twelve, Obanai was finally allowed to leave his cell. He was taken into a room that appeared to be an expensive shrine, and put face to face with the Snake Demon for the first time. The Demon remarked that Obanai was very small, and wondered to herself if she should wait to eat him until he was a little bigger. Deciding that she would, she organized his mouth to be cut wider, all the way to his ears, to match hers. The blood that he shed from this procedure was collected into a chalice that she then drank from.
Back in his cell with his wound now covered by a bandage, Obanai began only to think of escape and survival. He began to scratch away at the lattice of his cell with a stolen hairpin during the night, and by day he would be in a constant state of worry for fear that they could discover it. The only being he could trust was the snake that had strayed into his cage, Kaburamaru.
After a while of doing this, Obanai finally made his escape. As he ran, the Snake Demon began to pursue him, almost catching up to him and killing him before the Flame Pillar by chance came to his rescue. Because of Obanai's escape, the snake Demon had killed all fifty of his relatives and the only surviving member of his bloodline was his older cousin, who had also been saved by the Pillar. When they were reunited, however, Obanai's cousin rejected him, blaming him for their family's death.
Due to the effect his cousin's words had on him, Obanai joined the Demon Slayer Corps and decided to turn all his rage onto Demons, figuring that he'd feel like a better person if he risked his life for others.
As the other Pillars discuss what to do with Nezuko Kamado, Obanai, lounging in a nearby tree, inquires how they would deal with Giyu Tomioka's breach of the Demon Slayer conduct. When Tanjiro insists Nezuko would never harm humans despite turning into a demon, the Snake Pillar tells him to not make such reckless remarks, as the girl would obviously protect her family, and as such he cannot trust anything the young Demon Slayer says. Soon afterwards, he notes with interest that even though Giyu had interjected to stop Tanjiro and Sanemi Shinazugawa's brief scuffle, the former had still managed to land a blow on the latter.Upon Kagaya's arrival, the Snake Pillar descended the tree and bowed in respect to his superior. He then reiterated his distrust for Tanjiro and Nezuko when his leader asked for all of them to accept the two, stating that they all hate Demons. He subsequently listened as Kagaya's attendant read Sakonji Urokodaki's letter concerning Tanjiro and Nezuko, and how Sakonji, Tanjiro, and Giyu would all slit their stomachs should Nezuko ever attack a human. When Kagaya revealed that Tanjiro had come into contact with Muzan Kibutsuji, a mess of questions and arguments broke out, but Obanai and the other Pillars are silenced by a simple gesture from their leader.
After Sanemi purposely injured himself to bait out Nezuko, Obanai reminded his fellow Pillar that he would have to get out of the sunlight in order for her to appear. He then swiftly pinned Tanjiro to the ground to prevent him from interfering, maintaining his hold despite Shinobu's protests.
Tanjiro continued to struggle heavily, but before Obanai could do anything further to him, Giyu grabbed his hand, allowing Tanjiro to escape from his grasp. Obanai angrily removed his hand from Giyu's grip, demanding to know what he is planning. The Snake Pillar was then chastised by Kagaya for his treatment of Tanjiro, causing him to reluctantly agree to refrain from such methods in the future.
Obanai appears at the very end of the mission, after Daki and Gyutaro were already defeated. He partially congratulates his fellow Pillar for the victory against the Upper Moon, but greatly emphasizes the grievous injuries sustained against the "weakest" Upper Moon. He pressures the Pillar into remaining with the Demon Slayers, pointing to the vacancy left by Kyojuro's death and the increase in losses of lower-ranking Demon Slayers. Much to his surprise, Tengen maintains that the younger Demon Slayers—especially Tanjiro—were "definitely growing."
Obanai was in charge of teaching proper sword techniques. He was strict, allowing little rest and giving out extremely harsh punishments. By the time Tanjiro arrived, he had tied up all the students that failed to meet his expectations, making them into a sort of obstacle course, there and had Tanjiro try to hit him while not hitting any of the students. He was especially harsh since Mitsuri had raved about Tanjiro in a letter, but after four days of this training, Tanjiro finally hit Obanai. Afterwards, Obanai told him to "get the hell out of there" and to never talk to Mitsuri again.
Obanai rushes to the Ubuyashiki estate after hearing the call that Muzan was there. However, Kagaya blows up the estate before he or the other Demon Slayers can arrive, killing himself, Amane Ubuyashiki, Nichika Ubuyashiki, and Hinaki Ubuyashiki while heavily wounding Muzan. Gyomei Himejima is the only Demon Slayer to know of this plan beforehand, as Kagaya knew the other Pillars would oppose his decision. After seeing Muzan, Obanai readies himself to unleash his first form on him, but Muzan transports him and the rest of the Pillars into his Dimensional Infinity Fortress. Obanai runs into Mitsuri and kills a group of Demons that she was fighting.
Later, he and Mitsuri encounter Nakime. Mitsuri jumps off a wall and lunges at the Demon, but Nakime uses her Blood Demon Art to erect a wall and send Mitsuri falling. Obanai jumps in and grabs her, getting her safely to another of the Fortress' pillars. As Nakime starts manipulating the Fortress in the hope of crushing the pair, Obanai is easily able to dodge. After Mitsuri tries to attack and was sent tumbling out of a window, Obanai tries to use his second form to decapitate the Demon. However, he too is sent out a window, expressing in a frustrated fashion how much of a pain Nakime's Blood Demon Art is to deal with, despite it not being very deadly.
Obanai is deeply in love with Mitsuri, but pride, nervousness and the fact that he feels he is not worthy of her due to his "filthy blood" keep him from being forthright. He gives her gifts, keeps correspondence through letters, and is protective of her, and, while she enjoys the attention he gives her, she never seems to realize his feelings.
Obanai hates Giyu for unclear reasons, though Obanai's temper may be a large factor in it.
Obanai also hates Tanjiro with a passion, even more than he hates Giyu. It started with Tanjiro's breach of Demon Slayer conduct and insubordination during the Pillars meeting, but intensified after Tanjiro interacted with Mitsuri during the Swordsmith Village attack and completed her Pillar Training with raving reviews. As the story goes on, Obanai shows something of warmth towards Tanjiro. An example is when Tanjiro gets slashed in the eye by Muzan, and Obanai jumps in to protect him.
Obanai seemed to deeply respect Kyojuro and held him in a high standard. He believed he was extremely powerful, expressing his disbelief when he died.
Despite Tengen's victory against Upper Moon Six, Obanai downplays this significant achievement to instead emphasize the extent of his injuries. Tengen, for his part, brushes aside Obanai's concerns, insisting on retiring and disagreeing with the latter's sentiment that the Demon Slayers were going into decline.
Abilities and Powers
As a Pillar of the Demon Slayer Corps, Obanai is a very powerful swordsman.
- Master Swordsman: As a Pillar of the Demon Slayer Corps, Obanai is one of the most powerful and skilled swordsmen in the entire organization. During the Pillar training, he taught sword skill revision training to the other Demon Slayers, further showcasing his skill with a sword.
- Enhanced Strength: Obanai possesses great amount of physical strength, as shown when he pins Tanjiro to the ground with great force, with Tanjiro stating that he couldn't move or breathe. Despite this, however, he is considered to be the second-weakest member of the current Pillars in physical strength after Shinobu.
- Enhanced Endurance: After being hit by Muzan's attack and being injected with his blood, he was able to keep on fighting alongside Giyu, unlike his other fellow Pillar, Mitsuri, who was greatly affected by the same attack.
- Unique Weapon: Like his fellow Pillars Mitsuri, Gyomei, Shinobu, and Tengen, Obanai wields a unique Nichirin Blade. His blade is similar in appearance to an Indonesian Kris Sword, with the sword's shape modeled into waves to complement Obanai's Breath of the Serpent techniques.
- Crimson Red Nichirin Blade: During the battle against Muzan, after manifesting a Demon Slayer Mark and remembering how Muichiro turned his blade red, Obanai puts all of his strength into gripping his blade, turning it to crimson red. Crimson Red Blades are extremely powerful, as they nullify a demon's powers and regeneration.
Breath of the Serpent (
- First Form: Weaving Slash (
壱ノ 型 委 蛇 斬り Ichi no kata: Ida giri?) - Obanai rotates and releases a circular slash in front of him.
- Second Form: Venom Fangs of the Narrow Head (
弐ノ 型 狭 頭の 毒 牙Ni no kata: Kyōzu no Dokuga ?): Obanai goes behind his opponent at blinding speed and lops off their head.
- Third Form:  - Obanai curves his sword like a slithering snake and quickly decapitates his opponent.
- Fourth Form:
- Fifth Form: Slithering Serpent (
伍ノ 型 蜿 蜿 長 蛇Go no kata: Enen Chōda?): Obanai using his bending sword, curves it right to left at incredible speeds. This technique is capable of decapitating multiple targets at once.
- The snake around Obanai's neck is named Kaburamaru.
- Obanai considers Kaburamaru as more of a friend than a pet.
- Obanai is not very strong in terms of physical strength as he is listed "a little weak" by Koyoharu Gotōge when asked about arm-wrestling strength between the Pillars.
- His voice actor, Kenichi Suzumura, is married to Tamayo's voice actress, Maaya Sakamoto.