Sanemi is a tall, muscular, and slender man with spiky white hair and large eyes. His face and body are covered with scars, accrued over his many years of fighting demons. He cuts his hair short somewhere in between the Functional Recovery Training Arc and the Demon Train Arc.
He wears a green-tinted version of the Demon Slayer uniform, unbuttoned to expose his chest, a white long sleeved shirt, white buckles around his shins and tabi socks with a pair of zori with green straps.
During his battle with Kokushibo, he loses his right index finger and his right middle finger.
Sanemi is abrasive, hot-blooded, and stubborn, often times impulsive and quick to lash out. The only person he displayed reverence towards was Kagaya Ubuyashiki, and only after realizing the man was much more than his outward appearance suggested.
Sanemi's cold, rude, dismissive behavior is the result of losing too many people he cared about in the past. When Genya joins the Demon Slayers in search of Sanemi, Sanemi hurls verbal abuses at him, but Tanjiro Kamado is able to tell Sanemi didn't truly hate him; and in fact still bore the same brotherly love he had for him in childhood. This was however never expressed outwardly as he tried to push Genya away from him and the Demon Slayers so he wouldn't be exposed to danger.
Because of all those he lost to demons, he harbors a deep hatred towards demons and is convinced that humans and demons can never coexist. When Sanemi makes up his mind about something, it is extremely difficult to dissuade him— he doesn't believe Tanjiro's insistence that Nezuko Kamado doesn't eat humans, and moves to prove his own point by stabbing through the box with Nezuko inside. After riling her up, he slashes his own arm to try and bait her into attacking him due to his rare blood's effect. Even after she doesn't, and Kagaya uses this as proof Nezuko won't attack humans, Sanemi doesn't truly accept the Kamado siblings.
Abilities and Powers
- Master Swordsman: Being a Hashira of the Demon Slayer Corps, Sanemi is one of the most powerful and skilled swordsmen in the entire organization. Sanemi's skills and sword techniques are incredibly powerful and refined, impressing even Upper Moon One Kokushibo, a Demon with hundreds of years of skill and experience behind him.
- Intoxicant Blood (Marechi): Sanemi's blood was revealed to be one of the rarest blood types, making it incredibly intoxicating and mouth watering to demons. It is also unique due to its intense potency that the smallest whiff of his blood immediately causes demons to salivate and lose focus, as his blood was able to affect the strongest of the Upper Moon Demons, Kokushibo. So far, the only Demon who is immune to Sanemi's blood is Nezuko, due to her own strong conviction and will not to eat humans that was even further cemented and strengthen by the hypnosis planted in her brain by Sakonji Urokodaki.
- Muscle Control: Sanemi has also shown the ability to manipulate his own muscles to close up and prevent fatal and mortal wounds from opening up and bleeding out during mid battle, as seen when he was fatally slashed and cut up across his abdomen by Kokushibo, he was still able to fight on by manipulating his own muscles to close up his wounds.
- Crimson Red Nichirin Blade: During the battle against Kokushibo, Sanemi strikes Gyomei's spiked flail with his sword, turning both of them briefly red. Later in the fight against Muzan, Sanemi, learning from his previous encounter, forcefully clashes his sword together with Giyu's turning both of their blades temporarily red. Turning your blade red grants you the ability to hamper the enhanced regeneration of Demons.
- Demon Slayer Mark: Later during the battle against Upper Moon One, Kokushibo, Sanemi awakened his own Mark that takes on the appearance of a single Paper Origami Windmill with two dots on both sides on his right cheek. The mark dramatically increases his power and abilities, as seen when Sanemi was still able to fight and contend with Kokushibo on even ground, despite being grievously injured and slashed across his abdomen. This shows that his physical endurance, strength, and tolerance to pain have been dramatically increased. However, he couldn't land a significant hit on Kokushibo without assistance from Gyomei and Muichiro. In addition, he would have been put into a near-death state twice by Kokushibo if it weren't for Muichiro and Gyomei's intervention.
- First Form: Dust Whirlwind Cutter (
壱ノ 型 鹿 旋 風・ 削ぎ Ichi no kata: Jin senpū・sogi?) - Sanemi dashes forward in a cyclone of slashes.
- Second Form: Claws-Purifying Wind (
弐ノ 型 爪 々・ 科 戸 風Ni no kata: Sōsō - shina to kaze?) - Sanemi sweeps onward and creates four claws-like slash towards the enemy.
- Third Form: Clear Storm Wind Tree (
参ノ 型 晴 嵐 風 樹San no kata: Seiran fūju?) - Sanemi sweeps his sword in circular movements to redirect enemy attacks.
- Fourth Form: Rising Dust Storm (
肆ノ 型 昇 上 砂 塵 嵐?, Shi no kata: Shōjō sa jinran) - Sanemi sweeps his sword horizontally and create multiple cyclone of slashes to deflect enemy attacks.
- Fifth Form: Cold Mountain Wind (
伍ノ 型 木 枯らし 颪Go no kata: Kogarashi oroshi?) - Sanemi strikes from above while falling in a multitude of arced slashes.
- Sixth Form: Black Wind Mountain Mist (
陸ノ 型 黒 風 烟 嵐Roku no kata: Kokufū Enran?) - Sanemi unleashes a powerful vertical side way slash upwards at his target.
- Seventh Form: Gale - Sudden Gusts (
漆ノ 型 頸 風・ 天 狗 風Shichi no kata: Keifū - Tengu kaze?) - Sanemi leaps into the air while swinging his blade which generates gale-force winds to shred his opponent apart.
- Eighth Form: Primary Gale Slash (
捌ノ 型 初 烈 風 斬り Hachi no kata: Sho rekkaza kiri?) - Sanemi leaps into the air and swings his blade which generates circular torrents of wind.
- Ninth Form: Idaten Typhoon (
玖ノ 型 韋 駄 天 台 風Ku no kata: Idaten taifū?) - Sanemi preforms a backflip into the air and while upside-down, swings his blade to release a circular gust of wind.
- In the first character popularity poll, Sanemi ranked 15th with 207 votes.
- As revealed during his bout against Giyu, Sanemi loves ohagi, and he frequently cooks it. However his pride refuses him from saying anything about it.
- Like Kiyoshi, Sanemi is a marechi, and his blood is considered even rarer for a marechi as it can intoxicate demons and disrupt their senses and movement speed.
- Sanemi always keeps his uniform open, as he is proud of his muscles.
- Sanemi owns a Japanese Rhinoceros Beetle.
- Sanemi lost his right index finger and right middle finger in the battle against Kokushibo.
- (To Genya Shinazugawa) "You should've gotten married, had some goddamn kids, and lived until you became a goddamn old geezer. For all the times we couldn't do a thing for mom, and for all the times we couldn't do a thing for our little siblings, you should've made your goddamn wife and kids happy as they would have been. Because I would've made sure that no demon would be heading your way..." 
- (To Kokushibo) "How dare you dice my little brother up, you fuck-eyed bastard! You're dead! Dead! Unforgiveable!!"