Obanai is a young man with a short stature. He has a light complexion with black hair. His hair is fashioned to be choppy and layered with two strands of hair in between his eyes. Obanai has heterochromia—his right eye is yellow and his left eye is turquoise.
He wears bandages wrapped around his mouth and has a snake that wraps itself around his neck. Obanai wears a standard Demon Slayer uniform with a black-and-white-striped haori. For footwear, he wears a blue strapped zori.
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 Slaying 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 Slaying 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 obvious to most of their companions save for Tanjiro Kamado and Mitsuri herself; he gave her socks 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.
As the other Pillars discuss what to do with Nezuko Kamado, Obanai, lounging in a nearby tree, inquires how they would deal with Giyu's breach of 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'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 Tanjirou 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 Urokodaki Sakonji's letter concerning Tanjirou and Nezuko, and how Sakonji, Tanjiro, and Giyu would all slit their stomachs should Nezuko ever attack a human. When Kagaya revealed that Tanjirou 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 Kanroji again.
Obanai rushed to the Ubuyashiki estate after hearing the call that Muzan was there. However, Kagaya blew up the estate before he or the other Demon Slayers could arrive, killing Kagaya, Amane, Nichika, and Hinaki while heavily wounding Muzan. Gyomei Himejima was the only Demon Slayer to know of this plan beforehand, as Kagaya knew the other Pillars would oppose his decision. After seeing Muzan, Obanai was about to use his first form on him, but Muzan transported him and the rest of the Pillars into his Dimensional Infinity Fortress. Obanai ran into Mitsuri and killed a group of demons that she was fighting.
Later he and Mitsuri encountered Nakime. Mitsuri jumped off a wall and lunged at the demon, but Nakime used her Blood Demon Art to out of a walk and send Mitsuri falling. Obanai was agile enough to grab her and get her to another pillar. As Nakime started manipulating the fortress to crush or trap the pair, Obanai was easily able to dodge. After Mitsuri tried to attack and was sent tumbling out a window, Obanai tried to use his second form to decapitate the demon. However, he was sent out a window to. He also expressed that Nakime’s Blood Demon Art wasn't deadly, but it was extremely annoying.
Obanai is deeply in love with Mitsuri, but pride and nervousness 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 doesn't seem to realize his feelings.
Obanai hates Giyu for unclear reasons, through 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.
Obanai seemed to deeply respected 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
Breath of The Serpent: A breath style that focuses on twisting and bending the sword like how a serpent slithers. It bears resemblance to Mitsuri's Breath of Love Style, but his sword is much more like a typical sword with a blade that is shaped like how a snake slithers, while Mitsuri’s is long, soft, and more like a cutting whip.
- Second Form: Venom Fangs of the Narrow Head (
弐ノ 型 狭 頭の 毒 牙Ni no kata: Kyōzu no Dokuga ?) - Iguro goes behind his opponent at blinding speed and lops off their head.
- Fifth Form: Slithering Serpent (
伍ノ 型 蜿 蜿 長 蛇Go no kata: Enen Chōda?) - Iguro 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 his neck is named Kaburamaru.