Demon Slayers vs Muzan Kibutsuji: Part 2

Demon Slayers vs Muzan Kibutsuji: Part 2 is a battle between Demon Slayers Tanjiro Kamado, Zenitsu Agatsuma, Inosuke Hashibira, Kanao Tsuyuri, Hashira Giyu Tomioka, Mitsuri Kanroji, Obanai Iguro, Gyomei Himejima, Sanemi Shinazugawa, and Demon Yushiro along with the remains of the entire Demon Slayer Corps against Demon King, Muzan Kibutsuji. It occurs immediately after the Infinity Castle is destroyed.

Prologue
Kiriya Ubuyashiki realizes that Tamayo couldn't endure long enough to hold Muzan down and the medicine that both Shinobu and her concocted was unsuccessful in reverting Muzan back into a human. Kanata informs Kiriya that the first team of Demon Slayers have arrived where Muzan's flesh cocoon is resting and a second group is following them. Kiriya immediately orders her to tell the Demon Slayers to stay away from Muzan until all the Hashira arrive. Multiple teams of Demon Slayers surround the capsule of flesh that Muzan is residing in. A Demon Slayer hears an order from a Kasugai Crow that all the Demon Slayers should standby and not engage until the Hashira arrive as they have no idea on what can happen.

The Demon King Awakens
Suddenly, Muzan emerges from his flesh cocoon with a brand new appearance, his hair being far longer and being silver white due to his accelerated aging. He also has numerous jaws all over his body with sharp white fangs used to consume human flesh and blood, and is holding Tamayo's disembodied head on his right hand. Muzan massacres the dozens of Demon Slayers currently within his vicinity as they try to retreat from his location. Kiriya attempts to order them through a Crow for them to fall back. However, Muzan murders and consumes all the Demon Slayers within their groups and beheads the Kasugari Crow that gave the orders to retreat.

Muzan notes that due to him aging over a millennia, he has lost the desire to taste food however due to him starving for taking the force of the Ubuyashiki explosion and using his energy to nullify Tamayo's drug he now adores the taste of flesh and blood. He compliments Kagaya for "deliberately" bringing him humans to feast and to regain his strength and stamina. He even wants the new successor to bow down so he could possibly turn him into a demon since practically all of his subordinates are killed. Back at what's left of the Demon Slayer Headquarters, Kiriya commands his two younger sisters to make the second troop of Demon Slayers retreat and keep their distance away from Muzan as he'll only regain more strength and stamina from consuming more flesh.

Muzan lifts Tamayo's disembodied head and mockingly points out that her "drug to turn back into a human" had no subtle change to his body. He also imitates her words that he'll fall into hell and that hundreds of people have spoken similar words to him and that it has never happened once. Tamayo sheds tears and begs Muzan to give back her husband and children, in which he bluntly tells her to die and head to her family that "she" killed. Thus, Muzan crushes Tamayo's skull and consumes her blood and cells. Due to Yushiro's Blindfold being within the vicinity, Yushiro immediately loses his balance and topples over onto a wall with nearby Demon Slayers questioning whether he is alright. Muzan continues massacring more and more Demon Slayers within his path continuing to gain more stamina. Kiriya screams and begs the Demon Slayers to fall back so they can not give Muzan more strength and sustenance along with Tamayo's sacrifice to not be a waste. Muzan notes that every single member of the Twelve Kizuki was of no use to him and that he'll slaughter the Demon Slayer Corps himself.

Kiriya panics and blames himself for giving the wrong orders and letting all the Demon Slayers be slaughtered by Muzan Kibutsuji. From this, he loses all his concentration on preparing the remaining Demon Slayers in order to take down Muzan. During all of this, Kuina repeatingly calls out his name for new orders but Kiriya does not respond, presumably not even knowing that she was calling him. Thus, Kuina slaps Kiriya out of his self-doubting situation much to Kanata's shock and yells at him to keep it together, even calling him "Oyakata-sama". She then states that the fight isn't over yet and that he still needs to give orders to the Demon Slayer Corps, whatever success it brings. This brings back Kiriya's confidence and concentration, thus he commands that all the Hashira must go to Muzan's location immediately along with all the Demon Slayers as reinforcements. A Kasugarigarasu Crow gives intel that Muzan has been fully revived and that all the surviving Hashira must gather at Muzan's location.

A Force of Nature
Mitsuri Kanroji and Obanai Iguro are the first to hear this message, with Mitsuri question herself what both she and Obanai have been doing the entire time while Muzan was revived. Obanai questions what effort he has done due to that Muichiro Tokito and Genya Shinazugawa have sacrificed themselves in order to defeat Upper Rank 1, Kokushibo. He points out that Nakime is not exactly harming them but stalling them for time so the least amount of Hashira can fight Muzan Kibutsuji. Obanai quickly grabs Mitsuri in order for both of them to get out of the situation they're in. Quickly realizing this, Nakime uses her Blood Demon Art in order to teleport Muzan Kibutsuji to Tanjiro and Giyu's location. Tanjiro sees Muzan in the flesh and rage immediately fuels inside of him while Giyu tells him to calm down. Muzan calls them incredibly persistent which sickens him to his core, as he always sees humans as beings who only care about vengeance for the deaths of their loved ones. With that being said, he says that those who are alive should be grateful for being alive and should stop wasting their lives on vengeance. This greatly shocks Giyu and Tanjiro as Muzan compares himself as a natural calamity. He clarifies that humanity cannot gain revenge on disasters no matter much damage or how many lives it takes away from the world. Tanjiro calmly points out that Muzan is being that does not deserve to even exist in the first place.

Tanjiro can not believe that he has never felt this cold towards a living being once in his life. He points out from Gyomei's explanation that Muzan cannot die from decapitation, from this he tries to figure out how they can expose Muzan Kibutsuji to the sun. The problem being that they have no clue on how to bring Muzan out of the Infinity Castle. Muzan immediately transforms his arms into long spiked tendrils that function like whips and flails them at both Tanjiro and Giyu. Giyu uses Water Breathing, Eleventh Form: Dead Calm in order to repel the flailing tendrils but gets cut in many places in his body along with Tanjiro. Tanjiro notes that Muzan's attacks are unbelievable in destructive power and lethality, as he is only dodging by instinct alone.

Until You Disappear From The Face of This Earth
Tanjiro however keeps his tenacity going and attempts to go through Muzan's tendrils in order to harm him in some way. Just as when he got within striking distance of Muzan, one of his arms slash past and cuts Tanjiro's right eye knocking him onto the ground. Before Muzan kills Tanjiro with one of his tendrils, Giyu grabs hold of Tanjiro and tells him that slashing Muzan is absolutely pointless since his strength can't even be compared to the Upper Ranks. Muzan scoffs at the Demon Slayer's efforts on stalling him until the sun rises as the sun can't penetrate deep within the dimensional reality of the Infinity Castle along if three Hashira are enough to stall him. This confuses Giyu and Tanjiro as Muzan specifies that both Mitsuri and Obanai were killed by Nakime when she crushed both of the lower halves of their bodies. Muzan keeps attacking the two Demon Slayers with his tendrils with Tanjiro falling over multiple times due to him not being able to his surroundings. Suddenly the Love Hashira Mitsuri Kanroji drops through the ceiling and stops Muzan's assault by using Love Breathing, Sixth Form: Cat-Legged Winds of Love.

Mitsuri believes that her attack harmed Muzan in some way, but to her shock, the Demon King is completely unscathed. Obanai appears helping Tanjiro get back up and tells him to back out of the fight if he keeps getting knocked down. Tanjiro is relieved to see Obanai and Mitsuri alive, while Muzan is both confused and livid at the fact the two Hashira that Nakime supposedly killed are still alive. Muzan shouts Nakime's name in fury and demands to know what she is doing, with Yushiro placing his Blindfold technique in front of her singular eye along with his fingers jammed into her skull possibly touching her nerves to command the Infinity Castle upwards towards the surface. Yushiro with his eyes blood red tells that Muzan has committed the gravest sin in the world, taking Tamayo away from him. This makes Yushiro scream in grief telling him to repent immediately and that he will be erased from the face of the earth.

Giyu takes this opportunity to try to harm Muzan Kibutsuji with Water Breathing, Fourth Form: Striking Tide along with Obanai using Serpent Breathing, First Form: Winding Serpent Slash. This distracts Muzan as he doesn't know whether to kill the Hashira or his remaining Twelve Kizuki member. The floor where the main battle is taking place between Muzan and the Hashira suddenly open, making everyone fall. Muzan lifts his right arm and closes his fist, crushing Nakime's face and most parts of her skull. Because of this, the entire Infinity Castle is collapsing while Yushiro knows that he can still take everyone outside as not all of Nakime's cells have disintegrated yet. With that happening, no one is able to have solid footing while Mitsuri tries to presumably use another Love Breathing technique on Muzan which he dodges. Muzan flails his whips all over the place and slashes Tanjiro in his torso and nearly kills Mitsuri by impaling her face but Obanai pushes her out of the way, only cutting off a small piece of her haori. Tanjiro also javelin throws a broken Nichirin Sword from one of his fallen comrades at Muzan's skull, piercing it completely much like how he did against Akaza. Just as that happens, the Infinity Castle pierces through the terrain of the real world, flinging absolutely everyone in all directions.

Battle
Tanjiro opens his eyes and sees the night sky realizing that they are indeed on the surface, however the landed on a compact city with many innocent civilians. This is completely out of what Kiriya Ubuyashiki predicted where everyone would end out when the Infinity Castle would pierce through the world. Although since Yushiro and Muzan were in a tug-of-war on who could control Nakime, he says it is a miracle that they were even able to go to the surface. Kiriya asks Kuina how long there is left until dawn, with her pulling out a gold pocket watch and with sweating dipping down her face says in one and a half hours. This petrifies Kiriya as there is still so much more time left until the sun rises. A Kasugai Crow tells everyone that an hour and a half is left until dawn breaks. As the Hashira and all other Demon Slayers make out of the rubble, Muzan unleashes a large shockwave to push all the rubble on top of him. He angrily asks the Demon Slayers if they will really keep him in company until the sun rises and mockingly requests them to try.

A Struggle till Sunrise
The Hashira dodge Muzan's attacks and retaliate the Demon King with Obanai using Serpent Breathing, Third Form: Coil Choke, Mitsuri using her Love Breathing, Second Form: Love Pangs and Giyu using the Water Breathing, Eighth Form: Waterfall Basin. Obanai was able to slash his Nichirin Sword past Muzan's neck, but to no avail as the moment his blade cuts Muzan's neck it regenerates instantaneously. This confuses Mitsuri to the point where she doubts that Muzan is not being cut down, whereas Giyu knows that Muzan is being cut but regenerates his wounds instantly. Muzan finds this the perfect opportunity to strike and kill all the Hashira. Just as the Hashira were about to be mauled by Muzan, dozens of Demon Slayers come and sacrifice themselves to save the Hashira.

While the Demon Slayers keep sacrificing themselves, one of them tells the others to protect the Hashira with their lives as the Hashira always protected them. Mitsuri cries and yells at the Demon Slayers to stop as there have been too many casualties already. Tanjiro not wanting any more Demon Slayers to die stands up and tries to run back into the fight against Muzan but stumbles and falls, coughing out large amounts of blood. With his happening, Muzan comments that those who are wounded by him are bound for death as he points to Tanjiro slowly dying with the wound in his eye turning into a large clump of flesh. This greatly disturbs the Hashira, especially Giyu as Muzan explains that his blood is infused into his tentacles but those who do get injected with his blood do not convert into demons. Instead, their own cells begin to decay and get consumed by Muzan's blood "inevitably" leading to their death.

While Tanjiro lays dying, Nezuko Kamado stands up from her medical bed in front of Sakonji Urokodaki who is taking care of her. While Tengen Uzui and Shinjuro Rengoku see Nezuko sprinting away with Sakonji right behind her, Tengen yells at Nezuko asking where she is going to which she doesn't respond. Shinjuro informs Kiriya that Nezuko has ran off possibly exposing herself to the demons and even Muzan himself. Kiriya at first orders them both to get Nezuko back at their hands but someone with a swollen hand softly touches his shoulder, that being his father Kagaya Ubuyashiki. With his soft voice, Kagaya requests his only son to let Nezuko go and that she'll be fine. Kuina tells Kiriya that if a demon gets hold of Nezuko it'll all be over, and while Kiriya agrees with his sister's statement due to their father telling him to do so, it was the right thing to do.

Back at the battlefield with Tanjiro coming closer to death, the Hashira get slashed and cut by Muzan's attacks. Mitsuri gets the worst of Muzan's barrage and just as she was about to get impaled by one of Muzan's arm tentacles a sudden impact destroys that tentacle, saving Mitsuri. It soon turns out to be Gyomei Himejima, coming to everyone's surprise especially the Demon King's. As Muzan comments to himself that the aforementioned was one of the Demon Slayer's to have defeated his right hand man Kokushibo, Sanemi appears behind the Demon Lord and slices him vertically. As Muzan regenerates, the Wind Hashira throws multiple glasses of oil at the Demon Lord in which the latter whips all into little shards which spills the liquid all over him. Sanemi soon lights a match and tosses at the Demon, lighting him entirely on fire. With Muzan on fire, Sanemi states that it suits him as being dirty wanting to slice him to smithereens.

Near the battlefield, Murata is shown bruised from the debris of the Infinity Castle's remnants. He sees Muzan Kibutsuji, the enemy of his "family", wanting to help everyone else in defeating him. Before doing so, Giyu yells his name to take Tanjiro to a safe place and treat him. With no hesitation while carrying Tanjiro on his back, Murata realizes that Giyu has finally remembered his name for so long, ever since they met during Final Selection with tears coming down his eyes. He knows that even if there is a humongous difference in strength and status between them, he believes that they are still within the same batch. As Murata is recollecting his thoughts and opinions, Tanjiro still unconscious is receiving memories of his ancestor, Sumiyoshi.

Annihilation
Currently, Muzan's attacks keep getting fiercer adding more pressure onto the Hashira. Gyomei even points out that due to him not being able to access the "Transparent World", it is nearly a gamble to be able to dodge the Demon King's attacks with little to no injuries. Mitsuri however, is getting the worst of the Hashira, only being able to dodge purely by instinct and luck alone. This deeply impacts her resolve on being able to help her fellow Hashira defeat Muzan, she quickly plans on trying to get behind the latter and twist his arms behind his back in order to stall time and help the others gain some hits on the Demon Lord, even if she sacrifices her life doing so. While she evaluates her plan, she quickly realizes that she is getting pulled by one of Muzan's attacks that gives an appearance to a cyclone until it is too late. The attacks ruptures multiple tissues of flesh and skin off her left side: including her arm, abdomen and cheek/cheekbone. This immediately calls to Obanai's aid leading him away from the fight with Gyomei wondering what type of attack that was as he believes even Mitsuri should've been able to avoid that attack. With the other Hashira pressing on Muzan Kibutsuji, Obanai carries Mitsuri to a fellow Demon Slayer and orders them to find a "slant-eyed member" who carries strange papers with text on them.

Mitsuri however, still tries to get up and convince Obanai on letting her continue to fight, saying that she won't hold anything back this time and won't be a burden to anyone. Obanai quickly rejects while telling her that she has done enough to help the Demon Slayer Corps against the Demon race. While Obanai quickly sprints back into the battlefield, Mitsuri bursts into tears and begs Obanai to not die and neither should anyone else. As Mitsuri bawls, Obanai accepts to himself that he "must die" defeating Muzan in order to cleanse his own blood in order to reincarnate as an innocent being with the reincarnate of Mitsuri by his side. The bandages fall off, revealing a serpent-like slits across his entire cheeks. Obanai wants Mitsuri to know that he is a man from a distasteful family who have murdered people and take advantage of others for their own sake.

Multiple Kakushi are shown evacuating nearby civilians away from the battlefield by tell them that there are fires within the buildings along with the ground being unsteady and unstable. The civilians question if they are part of the government policemen, with them agreeing they are in order to not cause confusion and controversy. As some Kakushi give each other some sitrep/information about the evacuation of the city, one lone member hears the meow of a cat under some rubble. With that cat being Chachamaru, the Kakushi frees the cat of the rubble with it immediately sprinting straight towards the battlefield of the Hashira give the Kakushi that saved it no time to stop it.

While Hashira continue attacking, Obanai cuts off one of Muzan's arms while kicking it at the same time in order for the latter's instant regeneration to not reconnect his limbs instantly. Unfortunately it's of no use, as the Demon Lord regenerates his arm at blinking speed. As Giyu attempts to cut off one of Muzan's arms, the attack launches his broken blade off of his hands, showcasing his grip waning as a result of the poison from the former's attacks. Before one of Muzan's tendrils slashes and kills Giyu, both Obanai and Gyomei's spiked flail intervene and stop the tendril coming to Giyu's surprise. Sanemi throws a Nichirin Sword toward Giyu from a dead Water Breathing user, yelling at the latter to not dose off. Being ashamed of himself for letting his fellow Hashira down, Giyu picks up the Nichirin Sword and unleashes Water Breathing, Third Form: Flowing Dance at the Demon King.

Even Muzan can acknowledge the Demon Slayer's resilience, but knows that it is of no use as his poison will kill off all the Hashira long before dawn as the rest of the night will last for an hour and fourteen minutes. As he explains that in just five minutes, all their cells will be destroyed and they will die, making their stalling completely pointless. Suddenly, Chachamaru enters the battlefield above everyone opening the leather compartment to reveal four glass vials with lavender-colored liquid inside with it being sliced in half and beheaded by Muzan. As the vials are ejected onto the Hashira, the symptoms of Muzan's poison are being reversed. This greatly angers and frustrates Muzan as even after death, Tamayo continues to be a nuisance to him. With that, he creates multiple craters at the Hashira with them barely dodging the attacks.

Obanai comments to himself that his contribution as a Hashira are the lowest of everyone as he believes that he didn't land any crucial blows on the Demon Lord. While saying this, he knows that when someone is on the verge of death they can release explosive strength, with him "not being able to lift something heavier than chopsticks" and escaping his wooden prison cell. He compares himself to Muichiro who was able to change the color of his Nichirin Sword before dying, this greatly shocks him due to the common nature of one's blade not changing color more than once. As well as this, he was only able to do this with a powerful grip as told by a Kasugai Crow. Now fully knowing this, he accepts that one must grow past their own limits to defend everyone, with him unlocking his own Demon Slayer Mark and gripping his Nichirin Sword strong enough to change its color to bright red.

At first glance of his own Bright Red Nichirin Sword, Obanai thought that he had messed up in trying to make his blade red as his peripheral vision is almost completely white washed which falsely guided him with his blade's color. Being so eager in trying to make his Nichirin Sword red in order to combat the Demon Lord more efficiently, Obanai grips his blade with all his might despite him lacking much oxygen which in turn nearly makes him pass out mid-combat. As Obanai was commenting to himself, Sanemi yells to alert the former that one of Muzan's tentacles is coming straight for him. Giyu tries to save Obanai from Muzan's attack but was too late. However, Obanai is somehow up in the air, dodging Muzan's attack. The Demon Lord whips one of his arm's tentacles at the Serpent Hashira, but he somehow dodges it again. Adding to Muzan's confusion, his arm that attacked Obanai gets cut clean off without him seeing the cause. The Demon Lord analyzes who made the cut, that not being from Gyomei's spiked flail or his axe, not from Sanemi's blade as his blade doesn't make rigid cuts, and not from Giyu as he is only supporting the other Hashira. And it could certainly not be Obanai, as even though his blade just shined red, it could not have extended to reach his limb along with his dodging trajectory being odd, almost as if someone grabbed the Serpent Hashira away from the attack.

Reinforcements
The same cut happens again, with him realizing that only a blade with ridges could cut like that as it wasn't a clean cut. The Demon King suddenly realizes that "they" are here, realizing that they are invisible due to Tamayo's assistant's Blood Demon Art. Muzan lashes his whips at what seems like thin air but soon appears to be Zenitsu, Inosuke and Kanao along with the cutten blindfolds by Yushiro's Blindfold. Gyomei becomes surprised and exclaims with shock that they are still alive with Inosuke angrily responded that of course they are. With that being said he throws more of Yushiro's blindfolds everywhere making him shout that Muzan's attacks are pointless. Obanai is shown cutting both of Muzan's arms and some of his tendrils with a Serpent Breathing technique, and from seeing the deacceleration of the Demon Lord's regeneration Sanemi realizes that bright red Nichirin Swords do indeed have a purpose against Muzan. Kanao grabs one of the blindfolds that Inosuke threw, turning herself invisible and uses Flower Breathing, Fourth Form: Crimson Hanagoromo and Zenitsu also puts on one of Yushiro's Blindfold 's and attacks with Thunder Breathing, First Form: Thunderclap and Flash. Frustrated, Muzan angrily tells the Demon Slayers to stop their pathetic schemes, until Obanai interrupts him with Serpent Breathing, Third Form: Coil Choke.

Gyomei is thankful that Obanai's blade is still shining red and that the Demon Slayer Corps' man-power has increased now that Kanao, Zenitsu and Inosuke joined the fight. With this happening, he has enough time to clash his axe and spiked flail together turning them both bright red and demolishes part of Muzan's torso with his flail. Sanemi quickly alerts Giyu and strikes the latter's Nichirin Sword with his own, turning both their blades bright red. A Kasugai Crow informs everyone that there is one hour and three minutes left until dawn, with Sanemi saying that that is more than enough time to rip the Demon King to shreds. Meanwhile, Yushiro injects Tanjiro with another antidote for Muzan's poison with Murata concerned if he has injected with too much. Infuriated, Yushiro says that a lot of time has passed since Tanjiro took Muzan's attacks thus him being in such a bad shape. Yushiro then questions what Murata is doing with the latter saying that he trying to make Tanjiro let go of his Nichirin Sword. Suddenly Tanjiro's pulse comes back and regains consciousness with him opening his remaining eye. Back on the battlefield, Goto is shown seeing everyone overpower Muzan and is brimmed with hope that the Demon Slayers will defeat Muzan Kibutsuji. Sanemi puts on one of Yushiro's Blindfold's and when he does, he sees Inosuke exclaiming to the others that he also wants to have his blades to be bright red. Sanemi yells to Inosuke that he isn't strong enough and uses Wind Breathing, Seventh Form: Gale, Sudden Gusts on Muzan. With enough time to fully concentration, Gyomei tries to re-enter the Transparent World (きる) by listening for echoes from the Demon Lord's body just like against Upper Rank One Kokushibo. He succeeds and visualizes multiple hearts and brains throughout the Demon Lord's body. Despite the overall complexity of organs and their functions, the Demon Lord was still able to create multiple of hearts and brains thus explaining him being able to survive decapitation so easily. Along with this, they do not have a fixed location as they always move around making them incredibly difficult to hit. However, he tries to make the most of the situation and aids other by helping them access the Transparent World, specifically Obanai Iguro for a split second could see through Muzan's body and his hearts and brains.

Suddenly, Muzan Kibutsuji flails his tendrils and arm tentacles even crazier than before, causing a huge ruckus and shaking where even Goto felt it out of the battlefield. He peeks over and sees none of the Hashira or other fellow Demon Slayers fighting Muzan and wonders what happened. As he peeks over even more, he sees Gyomei crashed into the building he was hiding behind with his left leg knee-down completely demolished. Sanemi was launched onto nearly the top of a nearby building, Giyu crashed on the bottom of another with his right arm cut off, Obanai and Zenitsu were thrown to another building and Inosuke collapsed onto the ground with one of his Nichirin Swords broken.

Let's Finish This, Muzan
After all the Hashira, Inosuke and Zenitsu were knocked down by Muzan Kibutsuji, Kanao remains the sole fighter in the field despite being on her knees, drenched in blood and her Nichirin Sword is broken. As the Demon Lord continues to walk towards her, she tries to will herself to fight, and just as she tries to prepare herself to defend against his incoming strike, Tanjiro Kamado joins back onto the battlefield with the help of Yushiro's medicine, and uses Hinokami Kagura: Beneficent Radiance to cut off both of Muzan's arms and rescue Kanao. As Tanjiro brings Kanao over to Goto, he apologizes for being late to help everyone to defeat the Demon Lord and requests Goto to take care of her. As Tanjiro looks back to Muzan, the two converse, with the latter being abhorred with Tanjiro's wounded appearance asking him of who is real demon, while the Demon Slayer, enraged at his allies' injuries, calls on the Demon King to end their long-standing feud.

Shining as Brightly as The Sun
Tanjiro reflects on his memories and visions, noting that, now that he has seen the actual Breathing Style from Yoriichi himself, he has noticed the proper technique and style for performing the dance, including the correct wrist angles, footwork, breathing rhythms. As he still has access to the "Transparent World", he thanks Yoriichi for saving his ancestor and for passing down the Sun Breathing, and realizes that the twelve forms were to be connected until the break of dawn to stall the Demon Lord. Although Tanjiro still doubts his own abilities, due to even Yoriichi not being able to kill Muzan, he steels his resolve, recalling Kyojuro Rengoku's words to him to keep his heart burning. With this, he engages his nemesis with the legendary Breathing Style.

As Tanjiro approaches, he notices Muzan's new tendrils in his thighs, realizing that the demon’s shapeshifting abilities led to the defeat of the Hashira and his friends. Meanwhile, Muzan enragedly attacks the advancing Demon Slayer, seeing the ghost of the mythical Yoriichi in the young boy. Despite Muzan's whips slicing Tanjiro, the latter shrugs off the attack, assessing that the Demon Lord has nine tendril-like whips on his back, eight more from his thighs and two arm tentacles and commences with Sun Breathing: Dance, Raging Sun and Fire Wheel consecutively. As Tanjiro begins using the thirteenth form, Muzan comments that creatures who catch a glimpse of death become even more tenacious of reaching their goal. In order to avoid death, he knows that one must open the door of strength and perception that are unnecessary during their regular life and that those who do not open that door will die but those that do don't. With Tanjiro turning his Nichirin Sword bright red without using his sister's Blood Demon Art, he has opened the door as well as the other Hashira. Tanjiro continues engaging the Demon King with Sun Breathing: Dragon Sun Halo Head Dance and Fire Wheel commenting to himself that he has connected six of the twelve forms of the Sun Breathing.

Tanjiro comments to himself that his own brain and heart are "spinning", while his lungs are being pummeled and his limbs are in so much agony that they're almost being torn completely off. As there is one hour left until dawn, Tanjiro continues to tell himself to focus and to not think about anything else except right now while his arms are getting numb and his Nichirin Sword is getting duller. However, he keeps focusing on that one second and tries to connect that one second and repeat it until dawn, thus Tanjiro continues with Sun Breathing: Fake Rainbow and Burning Bones, Summer Sun. Muzan himself realizes that the accuracy of the Demon Slayer's techniques are fading along his Nichirin Sword soon turning into normal. However, even while the Demon Slayer appears to have taken some hits from the Demon Lord, the remaining other attacks of his are being dodged and evaded. This greatly confuses the Demon Lord as Tanjiro's movements are lackluster and are nowhere near their peak due to his own poison. Along with that due to the poison, the accuracy of his techniques continue to fade thus making him more and more exhausted which was the completely opposite of the Thirteenth Form's purpose. On the contrary, Muzan still doesn't know why he himself can't kill a lone Demon Slayer who is deeply burdened with fatigue.

Muzan suddenly realizes that he is the one who is slow as this one-on-one duel would certainly not have lasted this long due to his poison within Tanjiro. After Muzan finally figures out he has aged over nine millennia, Tanjiro suddenly uses Sun Breathing: Solar Heat Haze followed by Beneficent Radiance only to be followed by Clear Blue Sky, Fire Wheel, Raging Sun and Flame Dance. Muzan angrily shouts towards the Demon Slayer to stop jumping all over the place only for the latter to continue with Sun Breathing: Fake Rainbow, Dance, Setting Sun Transformation, Burning Bones, Summer Sun, Dragon Sun Halo Head Dance and Sunflower Thrust. With that, he has successfully linked all twelve forms and has done Sun Breathing: Thirteenth Form, only to tell himself to keep doing it only faster and more accurately nonstop until dawn arrives.

On the other side of the battlefield, Yushiro, Murata and another Demon Slayer find Chachamaru mangled on the floor. Yushiro easily puts Chachamaru back together, him being happy that it is okay. This puts the others in shock as they had no idea that Chachamaru became a demon. They quickly give the other Demon Slayers the serum to Muzan's poison with Murata giving it to Goto who injects it to Kanao, and another Demon Slayer to Inosuke. Yushiro himself works on fixing Gyomei noticing that his destroyed leg is in really bad shape. He then prays to Tamayo to protect Tanjiro as much as possible.

Speaking of whom, continues to engage the Demon King with his Sun Breathing techniques. The young Demon Slayer notes that in order to increase the effectiveness of all twelve techniques to its maximum, he must aim specifically for each of Muzan's vital organs. Saying so, he attempts to reenter the "Transparent World" in order to locate the vital organs of the Demon Lord but is unsuccessful due to him not having sufficient oxygen. He then tries to use his sense of smell in order to locate the organs but soon loses his footing and is open to one of the Demon King's whips. However, someone saves Tanjiro from his impending doom, with Muzan's attacks hitting the building behind Tanjiro completely leveling it.

Driving The Demon Into A Corner
Tanjiro remembers a familiar scent and regains his senses, with the figure that saved him was recognized as Obanai Iguro. With happiness, he shouts Iguro's name but that happiness soon turns into shock from seeing his scarred face. Tanjiro then exclaims and worriedly asks the Serpent Hashira whether he lost his eyes because he protected him, to which Iguro denies and corrects by saying he received that injury a while ago and remarks that Tanjiro never stops worrying about people. As Muzan continues attacking the duo, Tanjiro says that he will assist Iguro, but he refuses by saying that he was pretty much already blind in his right eye and that he has Kaburamaru, his pet snake, to help him. As Iguro lets Tanjiro, the Demon King approaches and unleashes a massive attack that completely obliterated an entire chunk of a building.

As Muzan and Iguro trade blows, Muzan comes to realize that Kaburamaru is actually predicting his attacks and relaying the information to Iguro so that he can react to it appropriately. Tanjiro and Iguro continue using their Breathing Style techniques to pressure Muzan, while the Demon King comments that he should have been able to finish both of them of as they were burdened with fatigue but the aging drug was preventing him from doing so as it was sapping his strength to recover from its effects.

As the battle continues, Tanjiro realizes that he can't enter the Transparent World due to being so close to oxygen deprivation and comments on how even this 2 on 1 is incredibly difficult. Just then, he spots Muzan's body changing, revealing numerous old scars all over his body, which he surmised to be from Yoriichi's attacks which scarred him on a cellular level. Tanjiro then realizes that those scars are indirectly Yoriichi showing them where to strike Muzan in order to damage him. Seeing the scars himself, Muzan reminisces his first encounter with Yoriichi with great apprehension and displeasure, remarking that he looked weak and yet his attacks would wound his body to the point it would not heal even after a millennium, causing him to ironically call Yoriichi a monster instead of him.

Seeing the efforts of his fellow Demon Slayers come to fruition as he realizes Muzan is slowly weakening, he says that he cannot let them down and must see this battle to its end. Tanjiro comments that he has to do something about Iguro's blindness, and remembers that Yushiro's Blood Demon Art papers could help. The Kasugai Crow then announces that there is 40 minutes left before dawn, causing Muzan to suddenly flee, to which Iguro remarks that Muzan, unlike a samurai who has pride or a human being who acts on emotion, is a living thing that would do anything to cling onto his own life. As the Demon King flees, he thoughtlessly tramples on the corpses of the fallen Demon Slayers that he killed, which causes Tanjiro to tear up in anger and fling their swords at his body, to Muzan's annoyance. Iguro then approaches behind Muzan and pierces his body with his Nichirin Sword. Tanjiro then grabs Yushiro's Blood Demon Art talismans and tells Iguro to take them, which distracts him momentarily which gives Muzan and opening to attack him, causing him to let go of them. As a response, he tells Iguro to take three long strides to the right but realizes that he can't discern where they are because of their small size. Tanjiro then shouts for Kaburamaru to grab them, to which the snake does, allowing the both of them to use their vision in conjunction. With this, the duo continue driving Muzan into a corner and leave no room for him to escape.

The Tables Turned, Dawn is Nearing
With 35 minutes left before the sun rises, Muzan attempts to split himself into hundreds of pieces to escape, to which he realizes he can't, which he attributes to a third drug. Just then, Tamayo's memory appears in Muzan's mind, taunting him by saying that there actually four while the Demon King coughs up blood, which she reveals to be a cellular destruction drug. Tamayo then continues mocking Muzan by saying that the death that he has feared for so long is now right in front of him. She then continues to say that just as Muzan would do anything to live, she and her allies would do anything to kill him as well. The Demon King comments that usually, none of the Demon Slayer's attacks would mean anything to him, and that their bright red blades pale in comparison to Yoriichi's while regenerating shouldn't exhaust him. However, the four drugs that were developed completely turned the tables.

Muzan suddenly stops moving and shapes his torso into a grotesque and massive mouth to unleash a giant shockwave like attack that connects with both Tanjiro and Iguro, causing immense seizures, convulsions and rendering them unable to breathe momentarily. The attack even managed to reach Kiriya and his siblings as the shockwave hit Yushiro's talisman which transferred the attack to them. It is then revealed that there are 25 minutes left before dawn. As Muzan walks away, Inosuke rushes to intercept him. The Demon King then tries to use the same technique as before but realizes he can't possibly due to fatigue caused by the drugs. Trembling, Inosuke starts saying that Gyomei lost his leg, Giyu lost an arm, and the corpses of the Demon Slayers are those which he has shared meals with. He then demands that Muzan give them back or that he will die a million times to make up for it. Annoyed, Muzan attacks Inosuke, and lands a surprise attack from below him by reaching his transfigured arm into the ground, the jaws crushing Inosuke. Suddenly, Zenitsu arrives and slashes Muzan's arm to free Inosuke, telling him to pull it together and that Tanjiro is still alive. As Zenitsu and Inosuke continue fending off the Demon King's attacks, Zenitsu encourages Tanjiro by saying Nezuko is going to become a human again and that they will return to their family.

The Demon King then pushes Zenitsu against a building with his elongated arm, to which Inosuke slashes out of his way, causing him to be hurled towards another building. Tanjiro then realizes that a bright red Nichirin Sword may be able to nullify the effect of Muzan's Blood Demon Art on his nervous system by stabbing himself. At the same time, Muzan is enervated, being unable to even lift his own arms up. He then gets exasperated seeing Zenitsu and Inosuke getting back up, commenting that no matter how much he crushes them that they won't die.

The Beast, The Thunder, The Sun
As Inosuke continues to overwhelm the Demon King with Beast Breathing, Fourth Fang: Slice 'n' Dice, Zenitsu comes in with Thunder Breathing, First Form: Thunderclap and Flash, Godspeed with the latter noticing that one of his legs is. With him saying that, he utilizes the Thunder Breathing, Seventh Form: Honoikazuchi no Kami which hits Muzan in his torso. However, Zenitsu realizes that the cut is super shallow and that if he had a bright red Nichirin Sword it would've caused far more damage. Inosuke barges in with his Beast Breathing, Fifth Fang: Crazy Cutting followed with the Third Fang: Devour. Muzan stops his barrage with his shockwave technique and goes in to mutilate him with his tendrils, with Zenitsu trying to stop the Demon Lord from doing said action.

Thankfully Tanjiro saves Inosuke from Muzan's attack with Sun Breathing: Burning Bones, Summer Sun, the former then takes this opportunity to keep stalling the Demon King with Sun Breathing: Raging Sun, Fire Wheel and Beneficent Radiance. As he keeps attacking Muzan, he knows the latter can't utilize the shockwave attack consecutively as it takes time to charge up enough for insignificant damage. Along with this, every time he uses that technique his normal attacks slow down dramatically.

Tanjiro then uses Sun Breathing: Dragon Sun Halo Head Dance and goes in for Solar Heat Haze but coughs out blood which opens him for Muzan to swing one of his tentacle arms towards him but Inosuke saves him back with his Beast Breathing, Sixth Fang: Palisade Bite. This helps Tanjiro counterattack the Demon King with Sun Breathing: Flame Dance, Clear Blue Sky and Fake Rainbow. Zenitsu tries to push himself forward to help his two comrades by. With that, he begs the spirit of his cultivator/master Jigoro Kuwajima to push him in the back one last time. This gives him the strength to do Thunder Breathing, First Form: Thunderclap and Flash. This thus helps his two comrades unleash their respective Breathing Styles, that being Sun Breathing: Dance and Beast Breathing, Fifth Fang: Crazy Cutting with Tanjiro telling Inosuke to not stop attacking Muzan.

Saying this, he continues with Sun Breathing: Setting Sun Transformation, and tries to use Solar Halo Dragon Head Dance but he loses his footing stopping his attack in the Demon Lord's tracks. However, Zenitsu comes in with Thunder Breathing, First Form: Thunderclap and Flash, Godspeed, as he takes the hit from Muzan in order for Tanjiro to then use Sun Breathing: Solar Halo Dragon Head Dance, Raging Sun, and finally Sunflower Thrust which pins him towards a wall of a building. As Tanjiro cannot unleash any more techniques, he tries to hold Muzan down as much as possible until dawn arrives. The Demon King tries to slash and stab the young boy with his arm tentacles and tendrils but his left arm gets grabbed by Mitsuri Kanroji. Shedding tears she yells at Muzan it cut it out by ripping his arm clean off, sacrificing her both of her own arms in the process. Sanemi is then shown cutting Muzan's arm clean off with Wind Breathing, Eighth Form: Primary Gale Slash and pins it at another point in the wall, preventing it from reassembling back to the latter's body.

Dawn of A Thousand Years
With that happening, the Demon King's face and torso split apart vertically exposing huge jaws and teeth as he tries to consume Tanjiro in order to conquer the sun. The latter forces himself to not let go at all as it is almost dawn. However, Obanai goes in front of Tanjiro in the nick of time and shields him from Muzan's jaws. Sanemi shouts to everyone to keep holding as dawn has just arrived. As dawn arrives the very moment Muzan sees the sun, horror runs through his body and unleashes his Shockwave technique one final time knocking everyone back except for Tanjiro who's entire left arm gets torn off by the attack. Despite the chaos that's happening Tanjiro keeps holding on to his blade as hard as he possibly can in order to turn it bright red with him saying Kyojuro's words yet again "Set your heart ablaze!"

Miraculously, Giyu comes to Tanjiro's aid and with his other remaining arm grabs hold of Tanjiro's Nichirin Sword as well. With the might of both Demon Slayers, the blade successfully becomes bright red. As the blade becomes red, Muzan coughs out blood and with the sun shining more and more, he screeches at the top of his lungs with horror. Muzan then points out that if he shrinks himself he'll burn away instantly thus in order for him to have a chance to survive he must protect himself with a body/mass of flesh. Doing so, his body expands in all directions turning himself into a giant demonic infant. Coming to everyone's shock, the giant infant absorbs Tanjiro into its body and crawls around the building in order to get to the shade. Kiriya shouts and begs the Demon Slayer Corps to stop the Demon King from entering the shade.

Everyone tries as hard as they can to stop the giant infant from entering the shade, such as throwing bookcases and driving hard into him with cars. A dozen or more of Kakushi push a bus-train in order to block the infant from taking shelter from the sun. As the baby tries to topple over the bus-train and smash the Kakushi with its right hand, Sanemi leaps into the air and unleashes Wind Breathing, Ninth Form: Idaten Typhoon, chopping off the infant's hand clean off. As the Wind Hashira bails onto the floor, he cusses at the demonic infant begging him to turn to dust already. Just as the infant was about to topple the bus over, a chain of iron wraps around the giant's neck pulling it away from the bus-train.

Giyu comes back in the fight and uses the Water Breathing, Tenth Form: Constant Flux on the demonic infant but does not do nearly as much damage as the others due to him only having one arm left. Sanemi joins back in using Wind Breathing, Fifth Form: Cold Mountain Wind along with Obanai Iguro as Kaburamaru keeps putting on Yushiro's Blindfolds with the former using Serpent Breathing, Fourth Form: Twin-Headed Serpent

Despite all their combined attacks on the Demon King, it does not stop the giant infant from burrowing into the ground. As Gyomei's chain begins to snap, from inside the giant infant, Tanjiro continues to grip his Nichirin Sword as hard as he can making its bright red color linger. From this, the infant regurgitates a lot of blood from its mouth, stopping it from digging any deeper into the ground. Being unable to escape the sun in anyway, the demonic infant wails and bawls as it continues to disintegrate. Thus the Demon Lord Muzan Kibutsuji himself is finally dead and defeated forever.

Aftermath
Muzan's defeat while significant, would prove to be a costly victory for the Demon Slayers, leaving scores of members deceased, dozens mauled and heavily injured and many on the verge of death. The Hashira, Mitsuri, Gyomei and Obanai are dead. Muzan, in Tanjiro's consciousness, is driven by his desire for immortality, and so bequeaths his knowledge and power to the unconscious boy.

Tanjiro turns into a demon, starting a new battle.