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. He is partially blind as he can barely see out of his right eye.
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.
During their battle with Muzan, Obanai and the other remaining Hashira are attacked by the Demon's flailing whips, and Obanai is left with three long scratches over his eyes, rendering him blind.
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 by 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 Rank 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 Rank, and Shinobu Kocho later estimates that each Upper Rank is equal to three Hashira 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 Hashira 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; having given her her green socks which 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 Infinity Castle.
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 has an incredible sense of determination, continuing the fight against Muzan even after he is completely blinded and covered in wounds. His ability to protect Giyu and Tanjiro throughout the fight, as well as thanking Tanjiro for helping him see proves that Obanai is able to drop grudges and become friendlier with people he was rude to prior.
Abilities and Powers
As a Hashira of the Demon Slayer Corps, Obanai is a very powerful swordsman.
- Master Swordsman: As a Hashira of the Demon Slayer Corps, Obanai is one of the most powerful and skilled swordsmen in the entire organization. During the Hashira 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 Hashira 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 Hashira, Mitsuri, who was greatly affected by the same attack.
- Enhanced Speed: Although this may largely be down to the power of his crimson blade, Obanai is seen to be incredibly fast when in combat during his fight against Muzan. Even when blinded, he's able to swiftly jump in and save Tanjiro from what would likely have been a lethal stroke from Muzan's whips when he makes a blunder, and dodge many of his next attacks which instead annihilated the buildings in the surrounding area.
- Kaburamaru: Obanai, having always been partially blind in his right eye, developed a combat technique utilizing his snake Kaburamaru. Kaburamaru is able to read enemy attacks and then relay that information to Obanai. The full extent of this technique is demonstrated when Obanai is completely blinded by Muzan, but he is still able to continue fighting as if nothing happened.
- 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. Though by doing this, he put too much strength into his grip and almost fainted. Crimson Blades are extremely powerful, as they dampen a Demon's powers and regeneration.
- Demon Slayer Mark: During the battle against Muzan, Obanai awakened his own mark. That took the form of three snake like tattoo patterns with large dots, stretching from his right arm to the right side of his chest that then boosted all of Iguro's natural abilities, as seen where he was able to land powerful sword slashes against him, swiftly dodge and maneuver himself to avoid all of Muzan's immensely fast attacks, increase his physical stamina and durability allowing him to fight despite being severely injured and greatly enhancing all of his physical sense to the point that he could easily fight despite being blinded.
- Transparent World (
透き 通る 世 界Sukitōru Sekai?): During the battle against Muzan, after being instructed by Gyomei, Obanai managed to briefly access the Transparent World.
- Unique Weapon: Like his fellow Hashira 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 Serpent Breathing techniques.
Serpent Breathing (
- First Form: Winding Serpent 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: Coil Choke (
参ノ 型 塒 締め San no kata: Toguro Jime?) - Obanai curves his sword like a slithering snake and quickly decapitates his opponent.
- Fourth Form: Twin-Headed Reptile (
肆ノ 型 頸 蛇 双 生Shi no kata: Kei jya sōsei?) - Obanai leaps forward and performs a horizontal slash that slices through the target.
- 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 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 Hashira.
- His voice actor, Kenichi Suzumura, is married to Tamayo's voice actress, Maaya Sakamoto.
- His slit mouth is similar to that of the Japanese urban legend, Kuchisake-onna.