The more Tanjiro walked up the hill, the more he was overcome by fear. Throughout his life, Tanjiro barely showed any emotion, similar to his father Tanjuro. The only times he did were when he felt like he or his family were in danger, at those times he'd show emotions such as rage or sadness but never fear. Tanjiro was never afraid of anything in his life, that all changed just now. Tanjiro was feeling a mixture of fear and anger. He ran up the hill to his house. He smelled so much blood, he heard screaming, he also smelled an unfamiliar scent. Once he got to his house he finally saw what it was that was screaming. It was his little brother…Rokuta. Rokuta's last words would haunt Tanjiro forever.
"ONII-CHAN! ONII-CHAN! SAVE ME!"
Tanjiro tried to run and grab Rokuta but he was too late as a slash went across Rokuta's back. Blood began to pour out of his back and his screams were silenced.
"ROKUTA!", Tanjiro screamed as he began to hug his brother's corpse.
"Rokuta was only three years old, what kind of monster would do this?" Tanjiro thought to himself as he began to cry.
Tanjiro's thoughts would be answered as he looked up to see a man with pale skin, red eyes, and black hair. The man was wearing a white fedora and a black suit and tie with white pants and black shoes.
"Oh my…what is it we have here? Another child and you seem to be the eldest. Will you survive the transformation?" The man asked Tanjiro.
Tanjiro was confused by the man's words as he looked up at him with hate in his eyes.
"Are you the one that did this?" Tanjiro asked the man with a dark tone.
"Yes…my name is Muzan Kibutsuji, the demon king and who might you be-" Muzan immediately stopped talking as he noticed the earrings the boy wore.
The earrings that Tanjiro wore were hanafuda earrings. They showed an image of a sun rising over a hill. Muzan knew these earrings all too well, they haunted him to the core. But the earrings weren't the only thing that frightened him. His overall appearance, his red and black hair, his dark red eyes, and most of all that red flaming mark on the left side of his forehead. These were all attributes of THAT man, Yoriichi Tsugikuni. Yoriichi was the only man who ever injured Muzan.
Tanjiro slowly took out his hatchet and began to rush at Muzan, the fire mark on his forehead began to grow as his strength & speed increased. Because Muzan was still in his thoughts, Tanjiro was able to cut his left hand off and slit his throat. Tanjiro used the breathing technique his father taught him to attack Muzan and it was successful. Unknowingly a bit of fire was generated from this attack which burned Muzan. It also helped that Tanjiro's presence was erased from the battlefield so it was difficult for Muzan to sense his attack.
Muzan was even more scared now. This attack reminded him of the first time Yoriichi ever attacked Muzan. The flames as hot as the sun burned his skin, the fire mark on his forehead traveled down above his ear, his presence in battle suddenly disappearing, and that incredible speed & strength. Despite these similarities, Tanjiro's attack was nowhere near as powerful as Yoriichi's attack. Muzan was thinking this before, but now he was sure of it. This boy has to be the descendent of Yoriichi Tsugikuni.
"You asked for my name earlier, my name is Tanjiro Kamado, although my mother's former surname was Tsugikuni so you may call me Tanjiro Tsugikuni if you wish. But I suppose it doesn't matter as you will die soon." Tanjiro declared as he looked down at Muzan with dark eyes.
Muzan looked at Tanjiro with anger as he suddenly regenerated his hand and his neck healed. This slightly surprises Tanjiro. Tanjiro wasn't unfamiliar with demons but he didn't know they could regenerate. He'd only run into one in the wild but he was able to kill it by tying it up and leaving it to burn in the sun.
Muzan regained his composure and began to really show Tanjiro how much weaker he was than him. Muzan attacked Tanjiro by rushing at him and breaking his hatchet. The disarmed boy still remained calm as he used the severed blade from the hatchet to slash at Muzan. But instead of Muzan getting cut, the blade was cut into 19 pieces. Tanjiro begins to panic realizing how much faster Muzan was. Tanjiro didn't even see Muzan move. Muzan then grabbed Tanjiro and pinned him onto the Kamado house.
"You are impressive, boy. Being able to fight someone like me at your age of what, 12? However, you are nothing like your ancestors, you simply have their talents. But such potential would be wasted." Muzan exclaimed to Tanjiro.
Muzan wanted to turn this boy into a demon but he also wanted to kill him for attacking him. Muzan's ego was too big as he wanted to get at least one over Yoriichi by turning his descendant into a demon. Muzan began to forcibly feed his blood to Tanjiro. However due to Muzan being trapped in his thoughts he made an extremely crucial mistake that would be his greatest regret.
"Dammit, I gave him way too much blood. I gave him a little more than half of my blood. But now I have full control over him so it doesn't matter." Muzan thought to himself.
Tanjiro began to fall to the floor and began to scream in pain. Muzan watched as Tanjiro began to transform into a demon. Tanjiro's canine teeth began to grow into fangs, his eyes turned red as his black pupils began to go slit, his fire mark began to slightly cross his left eye and some can even be seen coming up diagonally towards his forehead on his right cheek, his nails grew to become sharp and he began to smell meat. He smelled the corpse of his family and Muzan smiled.
"Go on, Tanjiro, feast on your meal." Muzan said as he smiled sadistically.
Tanjiro began to feed on his family as Muzan laughed and began to walk away as he had other things to attend to.
"I'll find you and pick you up later. Don't run into any slayers." Muzan said as he left.
Tanjiro was done eating his family's corpse as he turned his attention to Nezuko's body rising. Nezuko survived Muzan's assault and she looked at Tanjiro in fear.
"B-Big Brother? What are you doing?" Nezuko asked in fear.
All Tanjiro could do was growl as he began to tackle Nezuko down a snowy hill. Tanjiro then began to claw at his human sister as she began to leak blood all over.
"Big Brother! Please! You're hurting me." Nezuko said as she cried to Tanjiro.
Tanjiro began to bite into Nezuko's neck. As Nezuko screams in pain her screams are soon silenced as Tanjiro snaps her neck. Tanjiro soon begins to devour Nezuko. But something is different. The more Tanjiro eats his sister, the more he gains his sense. By the time he finished eating, Tanjiro had realized what he did.
"Nononononono, please Nezuko. NEZUKO! PLEASE DON'T DIE!!" Tanjiro screams as he cries and looks at Nezuko's flesh.
"DON'T DO THIS! PLEASE!!" Tanjiro screams as he cries in the cold snow.
Tanjiro doesn't get any time to grieve. Tanjiro was then attacked as a sword came down to slash his back. Tanjiro was able to dodge the attack. Tanjiro looked to face his attacker. His attacker was a boy with black hair tied into a ponytail and blue eyes. Tanjiro was overcome with anger as he began to attack the boy.
"You bastard! I'll kill you!!" Tanjiro screamed at the boy as he attacked him.
The boy was able to defend himself from Tanjiro's onslaught. Tanjiro then began to slash at the boy with his claws as cuts appeared on the boy's chest, arms, legs, & even face.
"Damn, this guy's too fast, and his regeneration is even greater than that of an upper moon. If I don't decapitate him quickly, I'll most certainly die." The boy thought as he tried desperately to cut Tanjiro's head off.
Tanjiro began to emit pink fire from his open wounds from the black haired boy's sword cutting his skin. The fire burned the black haired boy's skin and he was then sent flying back due to Tanjiro kicking him in his chest.
"Dammit, his kicks are more powerful than his punches and that pink fire burns like hell. So that must be his blood demon art. He can ignite his own blood into pink flames, it also seems he can control it too." The boy thinks as he stands up.
"Pink fire? So this must be the ability I get when I become a demon. Let's see what else I can do." Tanjiro says as he clashes with his opponent again.
"This kid…I don't see any kanji in his eyes, so he can't be a part of the 12 kizuki. Even former kizuki have their kanji crossed out. But this kid has no kanji at all. So he must be relatively new to being a demon. If he's this much of a threat now, I don't want to imagine how strong he'll become after devouring more humans." The boy thought to himself as he & Tanjiro clashed.
The more Tanjiro fought the boy, the more he began to grow as a fighter and he gained new abilities. He could see through his opponent's body. He could see his muscles, his heart, & his brain. He could predict his opponent's attacks by looking at his muscle movements. Tanjiro picked up a stick and began to use the breathing technique that his father taught him. He began to use sun breathing, similar to how he used it against Muzan
"No way, this kid…he's using total concentration breathing. How? Did he copy it after seeing me or could he always use it? Dammit! This is a huge problem. I won't be able to counter this next attack. What should I do? Come on, Giyu! Think! Think! THINK!" The boy now named Giyu began to think to himself.
"This next attack is gonna pierce his left lung and kill him. Sun Breathing: Sunflower Thrust!" Tanjiro said as he tried to penetrate through Giyu's lung but Giyu was able to knock the stick down with his sword.
This didn't stop Tanjiro from penetrating Giyu's stomach. Giyu screamed in agony as the stick stabbed all the way through his stomach. However the stick broke under the strength of the attack. Giyu was sent flying back as Tanjiro saw the small but bloody hole in Giyu's stomach he began to drool at the sight of blood. Tanjiro ran towards Giyu and picked him up. Tanjiro pinned him onto the ground as he prepared to feast on Giyu. However, Tanjiro suddenly stopped.
"…I…I can't…eat…him. I…refuse to…become a…monster like…him." Tanjiro said to himself as he punched Giyu in the face once to knock him out.
Tanjiro then ran back to his to bury his family or what remained of them and went home. Tanjiro soon ran away to figure out what to do as Giyu began to wake up.
"…What? Where is he? Hm…the sun came up, he must've ran away. That guy was way too strong for a newborn demon. I have to report this to the corpse." Giyu stated as he began to limp away.