Two days later.
The Demon Slayer Corps had received good news: they had finally located the Kamado family home. To get there, Tetsuya traveled alone. Armed with the map provided by the Corps, he surged forward at speeds several times faster than sound, arriving at the mountain ridge in mere moments. There, nestled quietly, stood a small cabin.
He stopped a short distance away and frowned. "Something is... wrong..."
It was far too quiet. The Kamado house should have been full of life, yet now only an oppressive, eerie silence hung in the air. As he approached the half-open door, the thick, metallic stench of blood hit him like a wall.
"I'm too late." Tetsuya pressed his lips together and pushed the door fully open.
The scene inside was horrific. Blood everywhere, splatters on the walls, pools on the floor, along with severed flesh and corpses lying in grotesque positions. Children and adults alike, all slaughtered.
Muzan must have come here very recently. Even though the Demon Slayer Corps had mobilized nearly everyone to search for the Kamado residence, they had still arrived too late.
"Hah… Hah… Hah..."
Tetsuya narrowed his eyes. "Breathing…?"
Stepping carefully between the bodies, he spotted a young girl with long black hair, wearing a pink kimono beneath a black haori. She was still breathing, barely.
"Nezuko?"
Judging by her appearance, this had to be Nezuko, currently in the process of transforming into a demon.
Tetsuya sharpened his hearing and detected another faint breath. He turned and saw an adult woman, covered in wounds, also undergoing the demonic change.
'Kie?' This woman had to be Kie Kamado, Nezuko's mother. She had become a demon too?
This was different from the original story… Though of course, fiction could never be taken as absolute truth in reality.
Kie seemed to be rapidly losing her sanity. The moment she laid eyes on Tetsuya, her irises turned blood-red, filled with raw hunger. In an instant, she lunged at him.
Lightning crackled in Tetsuya's eyes. Using his precise control over electricity, he seized the bioelectric signals in Kie's body, freezing her mid-leap just two steps away.
Tetsuya sighed and extended his electrical manipulation further, this time directly into their minds. He amplified their rational consciousness, pushing the destructive demonic instincts to the deepest corners and allowing their human intelligence to remain dominant.
Both Kie and Nezuko froze in place, eyes widening. The bloodthirsty crimson glow in their pupils faded slightly, not disappearing entirely, but losing its feral edge. In that moment, they became aware of their elongated claws and inhuman fangs.
They had become demons.
With their human awareness slowly returning, Kie and Nezuko collapsed to the blood-soaked floor. Ignoring the carnage around them, Kie looked up at Tetsuya with hollow eyes.
"What… happened?"
Tetsuya explained gently, his voice calm and soothing to ease their shock. Once they understood the full horror of what had taken place, Kie broke down in tears.
Nezuko clung to her mother, staring sadly at the massacre surrounding them. "Mom… They're all…"
Tears streamed down the young girl's face.
"Nezuko…" Kie gently embraced her daughter, grief etched deeply into her expression.
They had lost their entire family.
A sound came from the doorway. A young man rushed in, only to freeze in horror.
It was Kamado Tanjiro. He stared in disbelief at the scene inside the house. 'Everyone… dead?'
"Mom! Nezuko?!" Tanjiro saw that they were still alive.
"Big brother!"
Nezuko ran to him and clung tightly. Both siblings burst into tears. Kie wrapped her arms around them, the only survivors of their once-large family.
Tetsuya stayed silent, letting them grieve. Once the sobs quieted, they turned their attention to properly burying the bodies and giving their loved ones a dignified farewell.
Kneeling before the freshly made graves, Kie wept softly. "Hanako, Rokuta, Shigeru, Takeo… May you rest in peace."
After praying for them, the three approached Tetsuya. Tanjiro had noticed that this man had been standing protectively near his mother and sister amid the corpses. His sharp sense of smell told him clearly that Tetsuya was not the killer, he carried the scent of someone who had come to help.
"Excuse me, sir… Who are you? Do you know what happened here?" Tanjiro asked, his voice trembling with desperate need for answers.
Tetsuya looked at the kind-hearted, determined young man and replied, "My name is Tetsuya. A demon named Muzan Kibutsuji, the Demon King, killed your family."
"Tetsuya-san! Where can we find Muzan?!"
"Please tell us…"
Kie and Nezuko's voices were thick with hatred, startling Tetsuya. He was surprised they could even utter Muzan's name without consequence.
He recalled that demons created by Muzan were normally bound by a deadly curse: if they spoke his name, their bodies would self-destruct. Without the future plot developments, Nezuko shouldn't have been able to resist that curse. And Kie, there was no reason she should have become a demon in the first place.
Could it be that when Tetsuya had manipulated their minds, shoving the demonic side to the very back of their consciousness, he had inadvertently made them different from other demons? Creating new, independent demons free from Muzan's curse?
Tetsuya sank into thought.
Tanjiro, meanwhile, studied the expressions on his mother and sister's faces. He understood the hatred in their voices, he felt it too. The brutal murder of his family was unforgivable.
Then he noticed something strange about them: crimson eyes, sharp fangs, long claws. Those were not human traits.
"Mom, Nezuko… you two…?"
"They've become demons," Tetsuya explained calmly. "I took control of their consciousness to suppress the destructive demonic instincts and preserve their human intelligence."
Shocked by both the revelation and Tetsuya's power, Tanjiro exhaled heavily. His mother and sister were not threats. Even if they were no longer human, they were still his family.
Tanjiro asked again, "So, Tetsuya-san… why did you come here?"
"To…"
Tetsuya gave a brief explanation of his purpose.
"The Blue Spider Lily? So those simple blue flowers are actually that important?"
Kie looked stunned. She had never imagined the modest blue blooms held such significance.
Meanwhile, Tanjiro stared at Tetsuya with unwavering resolve.
"Please let me join the Demon Slayer Corps!"
Now knowing that the monster who slaughtered his family was Muzan, and that the Corps existed to destroy him, Tanjiro made his decision. He would not allow such a creature to continue existing. Most importantly, he would avenge his family.
Tetsuya almost told him that the Muzan problem would likely be resolved very soon and his participation might not even be necessary, but he chose not to extinguish the young man's burning determination.
Instead, Tetsuya instructed Tanjiro to fetch a wooden box and gather every Blue Spider Lily he could find. In the end, Tanjiro would still carry a box on his back, just not with Nezuko inside this time. The world still moved in its own stubborn way.
Afterward, Tetsuya brought them all to the Demon Slayer Corps headquarters.
The experience of supersonic travel left Tanjiro screaming in terror, while Kie and Nezuko clung nervously to Tetsuya's sleeves, gripping his clothes tightly as the world blurred past at impossible speed.