Looking at Lady Tamayo, who spoke so naturally that one could hardly tell she was a demon, Tanjiro couldn't help but ask the question he cared about most.
"Can a person who has become a demon ever become human again?"
This question was undoubtedly asked on behalf of Nezuko.
His younger sister was currently captivated by Kael's cat teaser, lying on her back on the floor and batting at the crisp-sounding bells with her hands.
"Kael, I'll let you answer this question."
Tamayo turned her head to look at Kael.
"Theoretically, there's no problem."
Kael said without even looking up, continuing to tease Nezuko. Seeing her innocent and pure appearance, he could only think...
So cute, I want to keep her.
Hearing Kael's answer, Tanjiro suddenly became excited and shouted loudly.
"Please tell me! No matter the cost, I'll do anything!"
"I said it's only theoretically possible for now; it still lacks sufficient experimental data support."
"What experimental data do you need?!"
As he spoke, Tanjiro almost shoved his face right in front of Kael's, only to be pushed away with a look of distaste.
"I currently need the blood of the Demon King. Can you get it?"
"I can!!"
Tanjiro answered with unwavering determination.
It was just Kibutsuji Muzan's blood. The Demon King was already the target of his revenge; he might as well settle it all at once.
Having just started his journey, Tanjiro clearly didn't understand the gap between himself and Kibutsuji Muzan. After all, he hadn't seen many demons in total, nor had he ever fought the man.
"You should focus on becoming a Hashira first."
Kael replied indifferently.
"Hashira?"
Tanjiro was stunned for a moment. Then, Lady Tamayo took over the conversation, her tone gentle.
"It doesn't necessarily have to be blood from Kibutsuji Muzan himself. Blood from other demons is also valuable, as their power originates from the Demon King's blood. Ideally, it should be from members of the Twelve Kizuki."
"Twelve Kizuki, I've noted it."
Tanjiro repeated with a serious expression.
"Secondly, I also need to draw blood from Nezuko. Her current state is very special."
Kael added.
Tanjiro glanced at Nezuko and was about to speak when Kael raised a hand to his lips, signaling for silence.
"We have guests."
Tanjiro blinked, not yet understanding what that meant, when he suddenly saw a colorful temari ball pierce through the wall of the house, flying toward Tamayo.
"Whoosh—"
A friction sound like flint striking fire rang out.
Tanjiro felt a wave of heat rush toward him.
It was only then that he noticed Kael had a nichirin blade by his side all along. It was just that the latter's presence was so overwhelming that people tended to overlook the things around him.
The crimson blade edge sliced through the temari, instantly destroying it.
A faint stench filled the air.
This temari was a manifestation of a Blood Demon Art, and its texture was far tougher than it looked. However, before Kael's nichirin blade, such characteristics were hard to maintain.
Through the hole in the wall, two demons with special abilities could be seen in the courtyard.
"Oh, is there another swordsman from the Demon Slayer Corps?"
The Temari Demon, Susamaru, noticed the nichirin blade in Kael's hand, her voice sounding exceptionally excited.
These demons were all influenced by Kibutsuji Muzan's power; not only were their bodies mutated, but their mental states were also quite concerning.
This was normal. Kibutsuji Muzan's own mental health was a disaster, as he suffered from a severe case of Yoriichi Tsugikuni PTSD.
"A demon hunter and a demon together? What's going on?"
The Arrow Demon, Yahaba, asked in confusion. Although he had lost his eyes, the Blood Demon Art he had awakened perfectly replaced that sensory function.
"How interesting. We'll just kill them all together."
The Temari Demon didn't care about that; she just wanted to vent the tyranny and bloodlust in her heart.
"Are they Kibutsuji Muzan's subordinates?"
Tanjiro stood up and shielded Nezuko behind him, his expression solemn and tense.
Relying on his superhuman sense of smell, he could smell the Demon King's aura on the two demons, and it was much stronger than any demon he had encountered before.
"Found him! The demon hunter wearing hanafuda earrings that the Master mentioned!"
The Temari Demon noticed Tanjiro speaking and immediately threw a temari ball, intending to finish the mission first.
Kael's previous strike had caused her mindset to shift slightly, making her less inclined to play around.
The temari ball, infused with demon blood power, flew at an incredible speed, appearing as a series of afterimages on Tanjiro's retinas.
However, he had also undergone rigorous reaction training. Relying on instinct, he could have managed to dodge, but the temari ball suddenly doubled back in mid-air, changing its trajectory.
This made Tanjiro's dodge a waste of effort, instead leaving his center wide open for the temari ball.
Just as the ball was about to hit, a flash of fire crossed Tanjiro's vision, slicing the temari in two and turning it into two clouds of dark, foul-smelling blood mist in mid-air.
"Thank you, Mr. Sakuragi."
Tanjiro thanked him, his heart still racing with fear.
Judging by the power with which that temari had smashed through the wall, even if his forehead was hard, he probably wouldn't have been able to withstand that blow.
Actually, one couldn't say for sure.
"Quick reactions."
The Temari Demon frowned slightly. If the first time could be called luck, then Kael destroying her temari twice in a row was clearly a matter of pure personal strength.
"Mr. Sakuragi, these two demons have a very strong scent of the Demon King on them."
Tanjiro spoke up to warn him.
"What a keen sense of smell. We are the Master's direct subordinates, the Twelve Kizuki!"
As she spoke, the Temari Demon took off her outer robe, and four extra arms sprouted from her ribs.
Clearly, this Temari Demon had only recently been turned into a demon by Kibutsuji Muzan and hadn't even figured out the internal hierarchy yet.
Kael didn't say anything. With a flick of his wrist, he silently threw out a long needle.
"What's this?"
The Temari Demon didn't even have time to react. It was only when the long needle had completely sunk into her body and the Wisteria Toxin began to spread that she realized something was wrong. However, by then, it was too late.
The speed at which the toxin spread could be seen from the state of her skin.
The deep purple Wisteria Toxin had already followed her blood flow, spreading to her entire body.
Forget using Blood Demon Arts; the Temari Demon didn't even have the strength to stand now. She collapsed weakly, making wheezing sounds from her mouth like a broken bellows.
The Arrow Demon beside her followed in her footsteps in the blink of an eye.
"Wh-What did you do to us?"
The Temari Demon struggled to look up, shouting with eyes full of resentment.
"Don't worry, you won't die, but you won't be able to move for ten days to half a month."
Kael walked forward, skillfully took out a syringe, and plunged it into the Temari Demon's neck, drawing a full vial of blood.
For a demon, this small amount of blood loss was no more serious than a mosquito bite. With their regenerative abilities, they could recover in the blink of an eye.
But that didn't mean their blood could regenerate infinitely.
Even demons had to follow certain laws of conservation of energy.
This was merely the accumulation from the demon's previous consumption of humans.
Blood was the source of a demon's power. If they were deprived of blood for a long time, they would fall into a mindless frenzy, and in more severe cases, they would lose all ability to move.
Over the years, Kael had drained quite a few demons, so he was all too familiar with these symptoms.
Most demons with special abilities wouldn't last three days in Kael's hands. These two might fare a bit better, but they were expected to last a week at most.
The demon blood in different demons varied more or less, and these differences were manifested externally as different supernatural abilities.
There was great research value in this.
However, limited by the environment and his personal situation, Kael's research progress on demon blood was still quite limited, and he couldn't produce concrete results.
Perhaps only when he stopped being human one day would he truly be able to excavate the power contained within demon blood.
"Mr. Sakuragi, what happened to them?"
Tanjiro stepped forward and asked in confusion.
"It's just an extract of Wisteria Toxin. As long as the concentration and dosage are controlled, it can produce a paralyzing effect on demons."
Kael explained simply.
It sounded simple and easy, but it was far from it. It involved a series of advanced knowledge in pharmacology and botany, such as the storage and shelf life of Wisteria Toxin, as well as coagulation and neutralization.
Nevertheless, Tanjiro's eyes were still filled with a gaze as clear as a Siberian Husky's.
Though it was a bit impolite to say, Tanjiro was indeed somewhat illiterate.
Coming from a family of charcoal burners, it was already quite an achievement that they had taught Tanjiro simple arithmetic.
"Then could the blood from them satisfy your needs, Mr. Sakuragi? I just heard them claim to be the Twelve Kizuki."
When it came to Nezuko, Tanjiro's reaction was quite fast.
"To tell if a demon is one of the Twelve Kizuki, you just have to look if there are characters engraved in their eyes. These two are just brain-dead demons who've been PUA'd by their boss."
"PUA?"
"Brain-dead?"
Tanjiro showed a bewildered little look.
However, he still understood Kael's point—these two were not the Twelve Kizuki they claimed to be, and he couldn't help but feel a little disappointed.
"You... you're talking nonsense!"
The Temari Demon couldn't accept this reality and tried to argue, but Kael had no interest in paying her any attention.
"Hey, Yushiro, pack these two demons up and take them away."
Kael called out to Yushiro in the room.
"Why should I listen to you?!"
Yushiro shouted in irritation, but his expression changed in the next second.
"Yushiro, listen to Kael."
Lady Tamayo spoke.
"Okay!"
Yushiro felt deeply what it meant to be in a state of 'painful yet happy'.
However, this wasn't the first time he'd felt this way, and it could be said that he had grasped the true essence of being a simp.
"I've already arranged a new residence. As for the equipment here, I'll have people come and move it later. Leave with me tonight."
Kael said to Tamayo.
Seeing that demons under Kibutsuji Muzan had already found them, Lady Tamayo could only nod.
Even though there was a significant age difference between them, for some reason, Lady Tamayo felt that she was being led by Kael most of the time.
But following her heart, Lady Tamayo didn't mind this at all; she even enjoyed it a little.
"Tanjiro, you and Nezuko come with us too."
Kael continued to Tanjiro.
"Yes!"
Tanjiro instinctively straightened his back. After just a short time together, he had already been completely won over.
From this point of view, Lady Tamayo was indeed firm in her will; it had taken Kael so long to barely succeed in winning her over... The new residence Kael arranged for Lady Tamayo was also somewhat deliberate—it was just across the street from the mansion where he and Kanroji Mitsuri lived.
It looked simple and modest from the outside, but the interior was quite comfortable and luxurious. The decoration and layout were designed by Kael himself, and one could clearly feel the care put into it.
"How is it? It should satisfy you, right?"
Kael held Lady Tamayo's hand and gave her a tour. Although no emotion could be seen on Tamayo's face, judging from the pressure from her fingertips, she was certainly happy in her heart.
After all, in the era Lady Tamayo had lived through, the status and relationship between the sexes were quite different.
Kael's actions and attitude were still very effective.
"Tanjiro, you should also stay here for tonight."
Kael didn't forget Tanjiro and arranged a room for the siblings as well.
"Ah? Okay, Mr. Sakuragi."
Tanjiro was stunned for a moment before reacting, hurriedly nodding in agreement.
As for that unfortunate couple, Kael had other arrangements for them. He had established a large, near-modern hospital in the Azabu District.
This hospital was built specifically to study the existence of demons. It contained many medical instruments hand-crafted by Kael himself, and the basement was filled with 'canned demons' accumulated over the years.
There were naturally many results, including helping a few individual demons break free from Kibutsuji Muzan's control.
However, for demons like the Temari Demon, who had been demons for a long time and had eaten many people, their mental mutation was quite severe. Basically, they would end up being drained of blood and frozen into cans.
"Kael, it's getting late. You should head back."
Lady Tamayo said softly.
"Don't you plan on letting me stay the night?"
Kael feigned a sad expression. Seeing that their relationship had made a breakthrough, he was thinking of striking while the iron was hot.
"Then did you tell Lady Mitsuri?"
Lady Tamayo reminded him. It wasn't that she wasn't prepared, she just didn't want to hurt that young girl.
"..."
Kael was stunned for a moment. At this time, Mitsuri should still be at home waiting for him to return. That silly girl, if she hadn't been informed in advance, would surely stay awake on the bed with her eyes wide open, unwilling to sleep.
This was indeed a major oversight.
Kael scratched his head and had to change his tune.
"It looks like it'll have to wait until next time."
Lady Tamayo didn't say anything. She stepped forward, lightly stood on her tiptoes, and gave him her compensation.
"Clack clack!!"
A sound came from a corner on the other side of the wall.
"It seems there are still mice in this house. Do I need to find time to clean them out?"
Kael asked with a smile.
Lady Tamayo didn't speak, but gave him a pretty roll of her eyes. She smoothed out her kimono, which Kael had crumpled, returned to her original elegant sitting posture, and saw him out the door.