Tanjiro grew up on a mountain along with his younger siblings and parents as the eldest son of the Kamado family. At some point in his life, his father, Tanjuro Kamado, passed away, which led to his siblings treating him as a father figure.
Tanjiro was very loving towards his siblings, going out of his way to care for them. When one of his brothers accidentally knocked over a kettle, he protected him and received a burn scar on his forehead as a result. Tanjiro was responsible for selling charcoal in the nearest town in order to earn money for the family and appeared to frequent the town quite often, as the civilians there easily recognised him and regularly asked for his help.
During the Taisho Period. Tanjiro Kamado is living a modest but blissful life in the mountains with his family, composed of his mother and younger brothers and sisters.
On a snowy morning, Tanjiro is about to leave for the nearby town to sell charcoal, but his younger sister Hanako Kamado and brother Shigeru Kamado hold him back, begging for him to bring them along. Their mother intercepts, telling them how he wouldn't be able to carry them if they were tired. Takeo Kamado also expresses disappointment, initially hoping to cut wood with his elder brother that day. As Tanjiro starts making for the town, his sister, Nezuko Kamado, who is carrying their youngest brother, Rokuta Kamado, bids him farewell.
At the town, Tanjiro holds friendly conversation with the townsfolk, some asking for him to help them perform errands. After spending the afternoon at the town, he starts to make his way back home but is suddenly stopped by a man named Saburo. Saburo warns him of the dangers in the mountains, specifically Demons, and offers his place for Tanjiro to stay during the night.
After arriving back home the next day, Tanjiro returns to find his entire family slaughtered by a Demon, save for his younger sister Nezuko. Tanjiro picks her up and, while attempting to carry her to the nearest doctor, discovers that she has been transformed into a Demon and is promptly attacked by her.
While Tanjiro struggles to fend off the attack from his Demon-turned sister, Giyu Tomioka attacks the latter from behind, only for his attempt to fail as the former moves his target out of the way. Recovering quickly, the swordsman asks the youth why he protected the Demon. Tanjiro tells him it was because the creature is his sister. Looking at the maddened Nezuko, Giyu questions this statement before swiftly removing the girl from her brother's grip.
As Tanjiro called out to his sister in alarm, Giyu tells him not to move, stating that it is his job to kill Demons like Nezuko. The swordsman then listens to Tanjiro's attempt to defend his sister and explain their current predicament, in which he comments that her change in demeanour is simple to explain: any open wound bathed in Demon blood causes that person to become a Demon themselves, thus increasing their overall numbers. Tanjiro exclaims that his sister hasn't eaten any people, but Giyu reminds him that she had just attacked her own brother, shortly thereafter bluntly stating that there is no way to cure a person once they are turned into a Demon, despite Tanjiro's plea to the contrary. As Tanjiro continues begging for his sister's release, Giyu brings his sword up to Nezuko's throat.
Tanjiro then prostrates himself before the swordsman, begging for his sister's life. Giyu grows angry, stating that the youth has no authority over who lives or who dies as he was too weak to protect even his own family. He also refers to all of his talk about finding a cure for his sister's condition and his family's killer is ridiculous. Stating that neither he nor the Demon Lords would have any respect for such a miserable display, Giyu demands that Tanjiro prove his dedication to protecting his sister by drawing his axe. As the youth ponders these words, Giyu silently encourages him to find the resolve necessary to accomplish all of the lofty goals he had placed upon himself. He then stabs Nezuko in the chest, causing Tanjiro to throw a stone at him in fury.
Giyu blocks the stone with the hilt of his sword, avoiding another one of the projectiles as Tanjiro charges at him empty-handed. Seeing the attack attempt as only a simple act of emotion, the swordsman angrily drives the hilt of his sword into his attacker's back, knocking him to the ground. Staring down at the fallen youth, Giyu wonders where his opponent's axe was. Looking up, he sees the weapon spinning towards him through the air, and narrowly dodges it. He then muses over Tanjiro's clever strategy, realising that the child's plan had been to defeat him with the flying axe after he was knocked out.
Distracted, the swordsman is attacked by Nezuko, dodging backwards from her kick. Cursing himself, Giyu watches as the girl reaches for her brother, certain that she was going to devour him. To his surprise, she instead stands protectively in front of his vulnerable body before charging at him in rage. Giyu recalls Tanjiro's previous assertion that Nezuko wouldn't eat humans, noting that somebody a long time ago had said the same thing and had been killed regardless. He further reflects on the nature of Demons, in particular, the high amount of stamina lost during the transformation process, and what they do to alleviate the lost stamina and prevent starvation: eat humans, even those closest to them. Seeing that Nezuko was not following this example, Giyu sheathes his sword, incapacitating the unusual Demon with a barehanded blow to the neck.
While Tanjiro and Nezuko are unconscious, Giyu wraps the latter in a clean cloth and straps a bamboo muzzle-like tube across her mouth. When Tanjiro regains consciousness, the swordsman instructs him to visit a man named Sakonji Urokodaki at Sagiri Mountain and also to not take his sister out in the sun, vanishing swiftly afterwards. Before leaving the place where they grew up, Tanjiro and Nezuko dig graves to bury their family and pray for their souls in the afterlife.
Later that day, Tanjiro hides Nezuko in a small cave entrance in a mountain and goes to the nearby farm to buy a broken basket and a little straw and bamboo, comically insisting on paying as the owner was willing to give him the materials for free. Reaching the cave entrance, Tanjiro quickly assembles a basket large enough to carry Nezuko on his back, with a little help from her shrinking abilities.
Near sunset, Tanjiro is told by a villager that to reach Sagiri Mountain, he would need to pass through a perilous mountain where people were disappearing. Unafraid, he ignores the warning and encounters a way station with lights on, immediately smelling blood. He goes inside to check on possibly harmed travellers. Just as they enter, Tanjiro and Nezuko see a Demon feasting on three travellers he had just killed. When the Demon notices them, it feels something odd but quickly jumps on Tanjiro trying to strangle him while Nezuko replies with a kick powerful enough to rip the Demon's head off.
Even without a head, the Demon still commands its body to attack and grows a pair of arms on its head, much to Tanjiro's shock. As the body furiously attacks Nezuko, Tanjiro double headbutts the head in order to get an opening and pins it to a tree nearby. With half of the Demon restrained, Tanjiro goes to help Nezuko by tackling the body of the Demon and throws it off a cliff. Although he almost falls off, Tanjiro is saved by his sister. Despite causing it excruciating pain with the destruction of its body, the Demon does not die.
Tanjiro realises the Demon pinned in front of him smells different from the one he sensed in their house. Holding his knife, he contemplates whether or not he should kill the Demon, the hand of a figure wearing a Tengu mask touches his shoulder suddenly interrupting his thoughts. The mysterious man tells him he would be unable to end the Demon's life with such a blunt weapon. Tanjiro questions the man on how to properly kill a Demon, only to be told that he would need to figure it out himself. To the man's disappointment, Tanjiro is too compassionate and overthinks, accidentally letting the Demon perish by the sun's first rays. After the Demon's death, Tanjiro notices the man already giving a proper burial to the Demon's victims.
The Tengu-masked man introduces himself as Sakonji Urokodaki and asks if Tanjiro was the one Giyu spoke of in his letter, Tanjiro confirming the statement. Sakonji follows his question by scolding Tanjiro for his inability to make quick decisions, slapping him when he hesitates to reply to what he would do if his sister decided to feast upon a human. Sakonji states that Tanjiro lacks resolution, stressing that he must not allow his sister to harm another human under any circumstance, else he should kill both her and himself. Sakonji then tells Tanjiro to follow him, saying that he would be tested to see if he would fit the role of a Demon Slayer.
On their path, Tanjiro, while carrying Nezuko on his back, feels short-winded rapidly. Sakonji, despite appearing to be much older than him, is keeping an extremely fast pace with his steps seemingly soundless. Glimpses of Tanjiro's past strike his mind as they arrive at Sakonji's house. All worn-out, Tanjiro questions if he had passed the test, in which Sakonji replies the test would begin at that moment as the two start ascending a mountain.
While the pair scale the mountain, Tanjiro notices the thinness of the air and thick fog covering their sight. When they reach the top, Tanjiro becomes dizzy and feels weakness in his legs. Sakonji tells him to climb down to the house at the foot of the mountain by dawn, vanishing in the fog afterwards. Tanjiro, confident in his sense of smell, easily begins descending as he had memorised Sakonji's scent. However, he immediately encounters several traps, including tripwire triggering rock throwers, ramming wood trunks and covered pits. Tanjiro notices he is running out of air quickly due to the altitude of the mountain and begins focusing on his breathing. A heavily exhausted and injured Tanjiro manages to reach the house before dawn, Sakonji confirming Tanjiro passage of the test and accepting him as his student.
After Tanjiro wakes up, Sakonji explains his profession as a Cultivator, as well as how to join the Demon Slayer Corps: survive the Final Selection held at Fujikasane Mountain. To prepare him for this trial, Sakonji begins to train Tanjiro in the way of the sword. Tanjiro's training consists of regimens focusing to practice different skills a Corps swordsman should have. For endurance, Tanjiro would make his way up and down the mountain on a daily basis, improving his ability to evade traps and sharpening his nose, with Sakonji slowly increasing the danger levels of the traps to the point where Tanjiro thought his teacher wanted to kill him. For swordsmanship, Sakonji starts making him perform the same endurance process as before but instead wielding a katana as a way for him to start thinking of it as part of his own body. After descending the mountain, Tanjiro stands at the foot of the mountain and swings his sword several times until he felt like his arms would fall off. Next, Tanjiro learns from Sakonji about the intricacies of the weapon and the forces behind it as he starts slashing bamboo poles to train aiming and precision. For combat practice, Tanjiro learns how to break his fall and get up quickly with his katana as he spars with an unarmed Sakonji. For breathing, Tanjiro learns the proper forms of breathing, receiving blows to the stomach from his teacher when he fails to get it right.
At some point after the training had begun, Nezuko falls into an endless slumber, deeply worrying Tanjiro. Sakonji tries calling a doctor, but he mentions that there isn't anything wrong with her. Tanjiro has the feeling that at any day he wakes up, his sister would be dead. He keeps a journal which he writes in daily to remember what he learns from Sakonji and to also serve as something Nezuko could read once she wakes up.
Finally, after a year passes, Sakonji tells Tanjiro that there is nothing left to teach him, instructing him to prove himself by working upon the basics he had been taught. He is led to a giant boulder and his master tells him that if he can split it in half with his sword, he would be permitted to go to the Final Selection. While Tanjiro hesitates, overcome with doubt, Sakonji leaves without a word, his hand in the boy's training completed.
Tanjiro starts training by his own harder and harder for half a year, still not successful and thinking his skills weren't enough. One day, after headbutting the boulder in desperation, a shout for silence is heard by Tanjiro. A boy with a fox mask appears on the top of the boulder, scolding Tanjiro for his whining. Tanjiro does not understand where he came from, nor did he sense his smell. The boy proceeds to attack Tanjiro with a wooden sword, which the latter defends against using the hilt of his sword. Despite wielding a real sword compared to the boy's wooden sword, Tanjiro promptly receives insults from the boy and is knocked out after a short fight.
A girl with a fox mask is present next to him as Tanjiro wakes up. She asks if he was alright, but he is too impressed by the fox-masked boy's combat skills to respond. The girl proceeds to assure Tanjiro that she would watch over him and help improve his techniques. She clarifies her name as Makomo and the boy's name as Sabito. Makomo spends some time pointing out the defects and correcting the unnecessary movements in Tanjiro's techniques. Tanjiro comes to know that Makomo and Sabito were not siblings and they were raised by Sakonji, along with other children whom she implied had been watching over Tanjiro as well. Makomo instructs Tanjiro about the concept of the Total Concentration Breathing Technique: by expanding his lungs and bringing a lot of air to his bloodstream, his temperature would shoot up and his heartbeat would accelerate to become as strong as a Demon.
After six months had passed, Tanjiro learns with Makomo how to smell out an opening thread that goes from his blade to a spot in his opponent; once he can see this thread, a slash can be made perfectly. At some time, Tanjiro continues sparring with Sabito to improve what he had learned.
One day, a longer-haired Tanjiro faces Sabito, who held a real sword, in the simplest contest: the faster blade would win. For the first time ever, Tanjiro's blade reaches Sabito's mask and splits it in half. Sabito's face is revealed, holding a sad smile. Makomo and Sabito disappear while smiling and Tanjiro realises he had not split the mask, but rather the huge boulder.
Tanjiro is praised by Sakonji while also being told that Sakonji actually did not want him to participate in the Final Selection, lest he'd risk another one of his children being killed. Tanjiro cries as they hug and Sakonji urges him to come back alive. Sakonji cuts Tanjiro's hair and gives him a white mask resembling a fox with a sun symbol in the same place Tanjiro had his mark as a way to ward off evil. While leaving, Tanjiro tells Sakonji to give his best to Makomo and Sabito, surprising Sakonji with the fact his student knew the names of his long-deceased students.
Tanjiro arrives at Fujikasane Mountain and gathers around with the other contestants. A young boy with black hair and a young girl with white hair walk in and explain that Demons hate Wisteria flowers which grow abundantly until this area, even out of season. From this point on, there would be no more Wisteria, and Demons captured by the Corps roamed free. Their trial is very straightforward: survive for seven days. With determination, Tanjiro and the others march ahead.
Two Demons immediately start assaulting Tanjiro, but he quickly smells the opening thread while avoiding their advances and seizes the opportunity to decapitate both in a single strike. Sakonji had bestowed upon Tanjiro a special sword called the Nichirin Blade, which, at the decapitation of the Demon, would crumble its corpse, preventing it from regenerating and effectively killing it. Tanjiro smells a rotten scent when praying for the souls of the Demons he had just killed. Advancing closer to the centre of the scent, Tanjiro finds a fellow contestant running away from a giant Demon with several hands swirled over its body. The Demon tries to kill the contestant, but Tanjiro pushes himself to act, saving the boy. The Demon recognises Tanjiro as an Urokodaki student by his fox mask.
The Demon questions Tanjiro regarding current affairs to establish which period of time he was in; upon discovering 47 years had passed since his capture by the hands of Sakonji during his time in the Demon Slayer Corps in the Edo Period, the Demon becomes furious. The contestant refutes such a fact, stating that no Demon there should be that old. However, the Demon replies that not only had he survived for so long, he had also killed 50 people in his life, including 13 students of Sakonji, referring to Sabito and Makomo as notably strong victims and implying Tanjiro would be the 14th. Tanjiro recalls Sakonji teaching him that the strength level of a Demon is proportional to the number of humans it had eaten. Tanjiro notes his sense of smell had developed to the point where he can detect the strength level of a Demon by its decaying scent, explaining the rotten smell felt before.
As the Demon starts describing how it killed both Sabito and Makomo, Tanjiro starts breathing heavily. In an angry response, he charges at the Demon, slicing several of his arms, but is hit by a hook punch on his rib cage and thrown in the nearby tree, hitting his head and fainting. Tanjiro hears a call to waken from one of his deceased brothers while unconscious, regaining consciousness in the nick of time and dodging the Demon's onslaught. Shortly retaliating, Tanjiro cuts more arms from the Demon but realises that no matter how many arms he cut, more would grow. Tanjiro suddenly leaps very high in response to smelling the Demon's hands underground. While in midair, the Demon tries to take advantage and strike him down, but Tanjiro uses an improvised headbutt in defence, rolling forwards and positioning himself in range of the Demon's head.
Tanjiro used Water Breathing, First Form: Water Surface Slash and decapitates the Demon. Contrary to the Demon's belief that Tanjiro would feel disdain towards its existence, the young swordsman feels sorrow holding the hand of the Demon while its corpse crumbled, praying for God to not let it become a Demon again when it reincarnates. Tanjiro thinks to himself that all children trained under Sakonji that perished could be at ease now.
On the morning of the seventh day, Tanjiro and three other contestants are congratulated for having survived the trial. One fellow contestant seems aloof, another is still frightened about the trial he had just passed and the last one questions about when they would get their official Nichirin blades. The two children introduce the Demon Slayer uniforms and the ranking system ranging from the lowest to highest rank, in which the Final Selection survivors were of the lowest. A Kasugaigarasu is provided, which would fulfil the task of following the new Demon Hunters at all time for communication purposes, and a crow lands on Tanjiro's shoulder. Out of impatience for receiving his blade, survivor Genya Shinazugawa hits Kanata Ubuyashiki, one of the spokespersons. This prompts Tanjiro to roughly grab his arm and ask for him to calm down. The boy does not comply and Tanjiro breaks his arm in the process. Afterwards, each survivor is asked to choose an alloy for their Nichirin Blade to be forged from.
Sometime later, Tanjiro climbs down Fujikasane Mountain feeling a wave of weariness, his body in pain from the fatigue he had sustained from the trial with even the new uniform appearing too heavy for him to carry. Tanjiro is troubled by his emotions for not being able to hold a conversation with any of the Demons before killing them and thus losing the chance to ask about a way to turn a Demon back to a human.
A weary, grimy and bandage-covered Tanjiro, using a stick as a crutch, eventually arrives back at Sakonji's house. As he makes his way towards the entrance, he suddenly hears the front door being knocked down from inside. Nezuko walks out the house, much to Tanjiro's surprise of the awakening from her slumber. Tanjiro tries to reach her but falls to the ground out of exhaustion. Nezuko immediately picks him up and embraces him as Tanjiro starts crying out of relief. In the tenderness of the moment, Sakonji appears and embraces them both, weeping out of happiness that Tanjiro came back alive.
Fifteen days later, Tanjiro sights at the entrance of the house a man with a large woven hat with floral wind chimes hanging from it, covering his face. The man tells Tanjiro that he is called Haganezuka and he had forged the blade which would be used by Tanjiro. The young boy also introduces himself, inviting Haganezuka to come into the house and have tea, but is ignored and the swordsmith sits on the ground, unwrapping the Nichirin Blade. Haganezuka explains to Tanjiro the origins of the Nichirin Blade forging. Tanjiro still shows concern about Haganezuka being on the floor as his belongings would get muddy, but he is again ignored. Haganezuka suddenly lifts his head towards Tanjiro, revealing the Hyottoko mask he wore, similar to Sakonji's mask. Once Haganezuka realises Tanjiro had red hair and eyes, he calls him "The Child of Burning Crimson," much to Tanjiro's confusion. Inside the house, Haganezuka explains that the blade changes colour after being pulled from the scabbard, hinting that by Tanjiro's features, he might finally see a blade turning bright red. Tanjiro unsheathes the sword and the blade turned black, much to the frustration of Haganezuka. Sakonji comments on how he had never seen this shade of black and Haganezuka jumps on Tanjiro, blaming him for not receiving the chance to see a red blade. In that instant, Tanjiro's crow alerts him to go on his first mission to hunt Demons.
After some time, Tanjiro equips himself with a standard Demon Slayer uniform under his checkered haori. Sakonji explains to his pupil that the outfit he is wearing was made from a special kind of fiber. The fabric is designed to be breathable, moisture-repelling and non-flammable. It is strong enough to withstand low-level Demon fangs and talons. As for Tanjiro’s Nichirin Blade, it is stated that not much is known about its unique properties since not many people wield black swords. However, it is implied that few black blade wielders have managed to survive as long as others. Tanjiro brushes it off since he is going to do everything in his power to revert his sister to a human again, regardless of what colour blade he had. To ease his travels, Sakonji gives Tanjiro a large, custom-made box for Nezuko to rest in during the day. The materials were handcrafted out using an extremely light wood called ‘Cloud Mist Pine’, coated with rock lacquer to reinforce the exterior and durability. Tanjiro expresses his gratitude to his master and proceeds to instruct Nezuko to enter the box. Right before Tanjiro disembarks on his journey as a Demon Slayer, Sakonji straightens his pupil’s clothes and bids him farewell.
Upon sundown, Kazumi questions Tanjiro if they should rest for the night and continue their search tomorrow. The Demon Slayer refutes, stating that it is because ‘those creatures’ are active during the night, he can’t afford to rest. Tanjiro kneels closer to the ground, picking a new scent at their current location. He speculates that the Demon he is looking for is somewhere nearby. At this point, Kazumi deduces that Tanjiro might be an actual Demon Slayer and that Demons do exist. After confirming it was, in fact, a Demon, Tanjiro sprints past Kazumi and towards the source of the scent. Kazumi gets stunned by Tanjiro’s speed, and soon follows him, but falls far behind. Tanjiro yells out that a Demon’s at large before jumping onto a nearby rooftop. Hearing that Demons do exist, Kazumi confirms that Tanjiro is, in fact, a Demon Slayer.
Arriving at the source of the scent, Tanjiro hops off the roof and lands in an alleyway. He draws his sword, readying himself for battle. Tanjiro detects two different scents, a Demon and a female human. Despite the fact that no one was in sight, he could tell that the two were in fact underground. After finding the exact spot where the Demon’s scent is strongest at, Tanjiro proceeds to thrust his blade into the ground. Wounding the Demon, a pocket swamp dimension opens up, revealing the girl trapped inside. Tanjiro immediately sticks his hand into the ‘swamp’, grabs the unnamed girl and pulls her out. A Demon’s hand sticks out from the ground, holding a torn piece of clothing from the unnamed girl’s sleeve. The creature pulls his upper body out of the ‘swamp’, revealing himself to the Demon Slayer.
Tanjiro confirms that the Swamp Demon is capable of using Blood Demon Arts. As the wound on the Swamp Demon’s arm rapidly heals, Tanjiro questions where he was keeping the girls captive. The Swamp Demon does not answer. Instead, he grinds his teeth before sinking back into the ‘swamp’. Kazumi arrives in time to see the Swamp Demon disappear into the ground. Tanjiro promptly asks for Kazumi to hold the girl and for the both of them stay close to him for their protection.
Their next destination is to the north-northwest. Tanjiro and Nezuko head towards Mount Natagumo with Zenitsu and Inosuke. This mountain is covered with spider webs and is swarming with innumerable spiders. Leaving the cowering Zenitsu behind, Tanjiro and Inosuke head up the mountain where they run into fellow Demon Slayers entangled in spider webs.
In a dream, Tanjiro sees his ancestor, Sumiyoshi, bringing tea to a mysterious long-haired man who is sitting near Sumiyoshi's sleeping wife, holding their child and looking out into their garden. The man thanks him for the tea, and Sumiyoshi apologises to him for making him take care of his family when he's their guest. He tells him not to worry about it, also adding that he'll be leaving soon and that he can't keep eating meals for free like that. Sumiyoshi says that it's totally fine, since he owes him his life, and, when the man doesn't reply, he adds that he can at least tell his story since he has no successor at hand. The man tells him that there's no need, as masters of their craft will always find their way to the same place. He also says that Sumiyoshi shouldn't see him as some special kind of man, because that is what he is not. He says that he could not protect a single thing that was of worth to him and that he is a man of no worth, to which Sumiyoshi thinks in his head that the man shouldn't think of himself like that.
Tanjiro finally awakens from the coma he was in due to his injuries at Gyutaro and Daki's hands and is met by a shocked Kanao, who drops the vase she was holding and rushes to his side, asking him if he's okay. Kanao explains to him that he was unconscious for a whole two months and smiles as she says that she's so glad that he's finally awake. Goto enters the room with the castella he brought over, and Tanjiro thanks him, which greatly shocks the kakushi, who then yells to Kanao that she should've told someone Tanjiro was finally awake, before also yelling the news to Kiyo Terauchi, Naho Takada and Sumi Nakahara. The three come rushing over, cheering and crying, glad that Tanjiro is finally awake, and Aoi Kanzaki joins them shortly after, expressing her guilt and gratitude to Tanjiro for going to the Red Light District in her place.
Tanjiro asks them how everyone else is doing, to which Sumi and Goto reply that Zenitsu had awoken the day after the incident and had gone back on the job two days ago, and Tengen had made it back without any help from the kakushi, just with the support of his wives. Tanjiro expresses his gladness that they're okay, and asks how Inosuke is doing. Sumi and Aoi explain that Inosuke was very close to death at one point due to his bleeding and the poison circulating around his body, and Tanjiro says that he must just be hallucinating the boar-headed Demon Slayer on the ceiling of the room then. Everyone looks up, realising that Inosuke is indeed there, as he jumps down and lands at the end of Tanjiro's bed, saying he's impressed Tanjiro noticed him and boasting that he woke up a whole seven days before he did. As Inosuke continues ranting at him, Kiyo shows Tanjiro a picture of a honey badger and says that Shinobu said Inosuke was just like it, since he's nearly impossible to kill. Inosuke exclaims that he's immortal, but Goto says he's just a moron, which stirs up commotion in the room, with the former trying to attack the latter as Aoi attempts to hold him back. As they continue to argue, Kanao tries to tell them to be quiet, but they ignore her until she raises her voice and shouts that Tanjiro has fallen back asleep so they should let him sleep peacefully.
A week passes, and Tanjiro makes a full recovery. He asks Naho if he got a new sword as he chipped his old one, and Kiyo shows him a number of letters Hotaru sent him that tell Tanjiro to die and that he hates him, saying he has no sword for him. Tanjiro expresses his guilt at having Hotaru make so many swords for him since he keeps breaking them, but Sumi says that Demon Slayers break their swords all the time, so it's probably Hotaru's fault for taking offence to that. Kiyo suggests that he go to the Swordsmith Village to talk things out with Hotaru in person.
Tanjiro participates in the Hashira Training Program with the rest of the Demon Slayers. He completes every course with the exception of the course run by the Wind Hashira, as he is banned for attacking him in defense of Genya.
After his defeat, Muzan manages to turn Tanjiro into a Demon and transfer all of his emotions into him. Tanjiro, now a Demon, starts to attack the other Demon Slayers, prompting Giyu to attack Tanjiro in order to stop him. Inosuke rushes up to Tanjiro, pledging to stop him from his rampage, but after a flashback, he is unable to bring himself to hurt Tanjiro and Tanjiro reaches out his hand at Inosuke, threatening to attack.