I hate myself more than anyone. I always think I have to get my act together, but I end up cowering, running away, sniveling. I want to change. I want to be a competent person.
— Zenitsu Agatsuma to himself in You Must Master a Single Thing
Zenitsu Agatsuma (
Zenitsu is a young man with fair skin and downward-sloped, scared-looking eyes that fade from soft brown to gold. He has short, yellow hair of varying lengths, cutting off squarely at the ends where it fades to a darker orange color, that falls in front of his face in uneven bangs. Before he became a Demon Slayer, Zenitsu's hair was originally black, but it turned the color it is currently when he was struck by lightning during his training.
For some time following the battle at Natagumo Mountain, his limbs temporarily shrunk due to Demonic poison but were able to return to normal afterward thanks to the medicine given to him by Shinobu Kocho.
He wears a paler brown version of the standard Demon Slayer uniform, which consists of a dark brown gakuran jacket, a white belt around his waist and hakama pants that extend, as well as his signature white-triangle patterned, yellow and orange gradient haori. As well as this, Zenitsu also sports a pair of Kyahan, tied at the front in 3 white bows, with the same pattern as his haori, pale brown tabi socks and white-laced zōri.
Zenitsu comes off as a coward, as he often claims that he doesn't have long to live due to the dangerous job of being a Demon Slayer. He also has rather low self-esteem despite his strength, even considering himself useless as seen when he couldn't believe he had slain a Demon and tricked himself into instead believing that it was Shoichi, even though the latter was a young child who didn't possess any form of special Demon-slaying ability. Zenitsu is in a constant state of fear and always cries and tries to run away at the sight of danger, claiming he wants to live a modest, normal life, instead of that of a Demon Slayer.
However, despite these weaknesses, Zenitsu still wants to live up to the expectations others set up for him and will try his hardest when he needs to. He holds great respect and admiration towards his comrades and his deceased teacher, Jigoro Kuwajima, and his inner focus and drive in avenging him help to wash away his cowardice and second thoughts when he is in a pinch.
Zenitsu is also shown to be something of a wannabe womanizer, stemming from a desire to not be single should he be killed. He tends to hit on girls who he thinks are cute and asks them to marry him, much to their annoyance. This womanizing nature is shown to override his docile personality, in particular when he believes his comrades are "flirting" with cute girls, he soon snaps and goes in long hysterical rants and complaints. During these times, he is also shown to become physically aggressive, lashing out at them in frustration.
Before the raid on the Infinity Castle, Zenitsu gives off a different, more serious vibe as if he is focused on something important. This development occurred after receiving a letter from Chuntaro, which revealed his master's death and Kaigaku's role behind it. During his fight against Kaigaku, Zenitsu is stern and becomes enraged, causing him to angrily yell at him for disrespecting their cultivator. His sudden change surprises his ex-senior, as Zenitsu shows a more mature persona compared to his usual cowardice.
Enhanced Strength: Zenitsu has attained amazing physical strength though years of harsh training. Zenitsu can hold down Inosuke Hashibira with his bare hands and swing his sword in rapid succession at speeds faster than the eye can see without fail.
Immense Speed & Reflexes: Zenitsu is one of the fastest beings in the series. Even at the start of the series, his speed could easily evade the attacks and senses of several demons such as the Tongue Demon and Spider Demon (Son). As he progresses, his speed was enhanced to the point that his movements couldn't be comprehended and perceived by Upper Rank Demons, like Daki who harbors extrasensory perception, and Kaigaku, a user of the same breath style. Perhaps his biggest feat was when he could outmaneuver a weakened Muzan Kibutsuji and deal extremely significant amount of damage to him. While fighting the Spider Demon (Son), he was able to maneuver mid-air to dodge his poison attack. He is able to contest Daki's extrasensory perception and dodge her sash attacks which basically have no blind spot.
Immense Stamina & Endurance: Zenitsu has incredible stamina and endurance, complementing his immense speed. During the Sunrise Countdown Arc, he lasted around half an hour exerting himself to the fullest without tiring out in his battle against Muzan Kibutsuji, despite sustaining multiple deep wounds and injuries in his previous battle.
Keen Intellect: Even when fighting unconscious, Zenitsu has displayed incredible judgement and intellect. When fighting consciously, this ability is enhanced even further. This able was best exhibited during his battle agaisnt Upper Rank 6, Daki. When Inosuke Hashibira made an erroneous deduction of her weaknesses, Zenitsu correctly explicated that all they need to do is keep both demons' head disconnected to correctly kill them. After his bout with Kaigaku commenced, he was able to clearly think and process his movements and demonic abilities.
Tactical Intellect: Zenitsu, being a talented fighter, has incredible wits and cleverness, being able to judge his opponents abilities and powers and developing countermeasures, even with one one form available to him. He can also use this ability while asleep, shown during the Entertainment District Arc.
Enhanced Senses: Like all skilled Demon Slayers, Zenitsu possesses senses enhanced beyond a regular human level. This power is exemplified in his sleep, where he can discern his surroundings and detect the whereabouts of Demons in conjunction with his hearing.
- Enhanced Hearing: Zenitsu has a heightened sense of hearing, allowing him to detect danger from even the faintest of sounds. He can also hear people's thoughts, emotions and personality if he uses his sense of hearing to its fullest potential. He can also use this ability to locate Demons by comparing the sounds produced by a Demon's body to those produced by a human. Zenitsu has also displayed the ability to decipher layers upon layers of sound in one of the brothels and even in the Infinity Castle.
Indomitable Will: Like all Demon Slayers, Zenitsu possesses incredible willpower and spirit in order to kill Demons. This was displayed in the Sunrise Countdown Arc where, despite usually being a coward, he has shown incredible will, never giving up even in the face of Muzan Kibutsuji.
Master Swordsman: Zenitsu is an incredibly talented swordsman, towards the end of the series, his skill has been honed to Hashira-level. Zenitsu is especially talented in Iaijutsu.
Unconscious Combat: Zenitsu becomes stronger when he sleeps. When his life is in danger, the fear he experiences exceeds his limits and makes him fall unconscious, which is when he reaches his true potential; when Zenitsu is asleep, he can perform his swordsmanship at a high level based purely on instinct alone. This ability allows him to fight even after he falls victim to Enmu's sleep spells. As the story goes on, he continues to improve his skills and courage and depends on this ability less and less, allowing him to fight while conscious.
Thunder Breathing (
- First Form: Thunderclap and Flash (
壱ノ 型 霹 靂 一 閃Ichi no kata: Hekireki Issen?) - The swordsman unsheathes their blade, dashes forward at blinding speeds that mimic lightning ripping through the air and decapitates the opponent.
- Six Fold (
六 連Rokuren?) - An extension of the Thunderclap and Flash technique created by Zenitsu. Zenitsu performs the Thunderclap and Flash technique six times in quick succession while slightly augmenting the power his dashes.
- Eight Fold (
八 連Hachiren?) - An extension of the Thunderclap and Flash technique created by Zenitsu. Zenitsu performs the Thunderclap and Flash technique eight times in quick succession while slightly augmenting the power his dashes.
- God Speed (
神 速Shinsoku?) - An extension of the Thunderclap and Flash technique created by Zenitsu and the fastest version of the attack, even swift enough to evade the senses of Upper Rank Demons. During the first display of this technique, an unconscious Zenitsu remarked that he mustn't perform this technique more than 2 times, otherwise his legs would be rendered useless due to muscle fatigue and exhaustion. However, during the battle against Muzan Kibutsuji, Zenitsu has shown improvement in the use of this technique, allowing him to use it more than 2 times while still maintaining the power and speed of the attack.
- Kiwami (
極Kiwami?) - An extension of the Thunderclap and Flash technique created by Zenitsu. Zenitsu performs an Iajutsu slash and goes into the stance of the First Form, unleashing the original technique after. This technique is exclusive to the Kimetsu no Yaiba: Hinokami Kepputan game.
- Six Fold (
- Seventh Form: Honoikazuchi no Kami (
漆ノ 型 火 雷 神Shichi no kata: Honoikadzuchi no Kami?)  - Possibly the Thunder Breathing's most powerful technique and the personal creation of Zenitsu Agatsuma. Zenitsu's katana takes the form of a bright yellow dragon that seemingly emanates electric sparks and lightning as he dashes forward at blinding speeds surpassing his Godspeed technique and decapitates the opponent. The speed required to perform this technique was so immense it burned the air around Zenitsu and caused his haori to be ripped to shreds.
Standard Nichirin Katana: Like all Demon Slayers, Zenitsu harbors a standard Nichirin Blade. His blade is yellow in color with the words Destroy Demons engraved on the side. His hilt circular shaped with 4 slight indentations, the center has a silver tone with small triangles and has a golden border. He also carries a white scabbard where he stores his katana.
- Zenitsu's surname means "my wife" (我妻 agatsuma?), while his given name means "goodness" (善逸 zen'itsu?). His first name contains the kanji for "good" (善 zen?) and "special, unique" (逸 itsu?)
- Zenitsu's rankings in the popularity polls are as follows:
- Thanks to his hearing, Zenitsu is very skilled at playing the shamisen and the koto.
- Zenitsu has also been mispronounced by Inosuke. Examples including Monitsu (
紋 逸Mon'itsu?) and Chuitsu (チュウ 逸Chū'itsu?) in his dream as a squirrel squire.
- Zenitsu is a member of "Stylish Scruffy Democracy" band together with Tanjiro (Vocals), Inosuke (Taiko Drums), and Tengen (Harmonica). Zenitsu is the band's song writer and the Shamisen player. "Exploding skin and the melancholy of modern smell" is their debut song that made everyone who heard it feel dizzy and vomit non-stop. Zenitsu also wrote a song entitled "Previous Life's Sins".
- Zenitsu is the only non-Hashira Demon Slayer to have done feats specifically only Hashira have done:
- Zenitsu has an overbite.
- The pattern on Zenitsu's haori may be inspired by Uroko, a traditional Japanese pattern that symbolizes scales. Samurai would wear clothing with this pattern to protect themselves from harm.
- After the events of the story, Zenitsu wrote a memoir entitled "The Legend of Zenitsu".
- Zenitsu is superstitious as he was shown to be delighted seeing two tea stalks in his tea in the extra chapters. In Japan, seeing Chabashira or a tea stalk floating vertically in your teacup when you have Japanese green tea is a sign of good luck.
- It has been remarked by Zenitsu that his combat style focuses on channeling strength into the user's legs, and maximizing the output of every single muscle and blood vessel in them.
- There are six forms, but Zenitsu could only learn the first form said to be the basis for the others yet he honed it to where he could fight against several strong demons. He later created a seventh form and defeated his former senior who had become the Upper Rank 6 of the Twelve Kizuki.
- (To Tanjiro Kamado) "So you were carrying such a cute girl with you... You were carrying such a cute girl with you every single day... and going about your journey with such joy... Give me back the blood I bled for you!!!"
- (To himself) "I hate myself more than anyone. I always think I have to get my act together, but I end up cowering, running away, sniveling. I want to change. I want to be a competent person."
- (To Kaigaku) "Grandfather wasn't senile. If I'm scum, then you're trash. I feel sorry for grandpa for having such pathetic successors. I can only do the First Form and you can do everything except that!"
- (To Kaigaku) "This is my form. I created it, so it's all mine. With this technique... I wanted to fight you as an equal!"
- (To Tanjiro Kamado) "Tanjiro! Focus on staying alive! Can you hear me? Don't die! You can't die! Nezuko's gonna to be human again! And you're gonna get her out of here! And go back to the house where you grew up! Your family is waiting for you two to return!"