Before his death, Yoriichi had only one encounter with Muzan.
At that time, the Demon Slayer Corps had just recently introduced the breathing style principles brought by Yoriichi. Although it had narrowed the gap in strength between humans and demons, Muzan still believed that ordinary Demon Slayers still could not threaten demons.
Because of this, Muzan did not deliberately seek to eliminate the Demon Slayer Corps.
Especially after observing the mediocre performance of the elite swordsman of the Demon Slayer Corps, Muzan became even more convinced that, as a perfect being, he could not be defeated.
As a result, although Muzan had some interest in the breathing style at that time, this interest was quickly extinguished—until that day, when he encountered Yoriichi.
During that encounter, Muzan only fought once, but it ended up with Yoriichi delivering a devastating blow that left him unable to recover from his injuries, unable to regenerate his body, and on the brink of death.
At the end of that battle, Muzan fled, splitting his body into more than eighteen hundred fragments to distance himself from Yoriichi, and went into hiding.
From that moment onward, Muzan did not dare to show himself to the world until Yoriichi passed away.
Because of that encounter, Muzan experienced the fear of death for the first time since becoming a demon. He also felt deep fear toward the man who seemed to have been born to defeat him, leaving a lifelong trauma.
After that incident, Muzan no longer ignored the Demon Slayer Corps.
In order to completely eliminate the Demon Slayer Corps, Muzan created the Twelve Kizuki. Even after Yoriichi's death, he personally attacked the Corps, wiping out all the swordsmen who knew Sun Breathing, and cutting off any legacy of Sun Breathing.
Since then, the Demon Slayer Corps and the Ubuyashiki family, who led the Demon Slayer Corps, became thorns in Muzan's eyes and became the primary targets of the Twelve Kizuki. Over the centuries, they were pushed to the brink of destruction several times by demons, almost facing catastrophic destruction.
This was why the Demon Slayer Corps went into hiding, refusing to cooperate with the authorities, and began to conceal the whereabouts of their headquarters and the Ubuyashiki family.
All of this was because of one man—Tsugikuni Yoriichi.
He was the first human to instill the fear of death in the Demon King, Muzan, and the only swordsman in a millennium who almost killed him.
Tamayo was fortunate enough to witness the scene where Yoriichi almost killed Muzan.
Due to her expertise in pharmacology, Tamayo was turned into a demon by Muzan and kept by his side, trying to use her knowledge to create a drug that could overcome sunlight.
Because of this reason, Tamayo, who was always with Muzan at that time, could witness everything that happened that day.
"I really want to kill Kibutsuji Muzan, I dream about it..."
For the first time, hatred appeared on Tamayo's beautiful and dignified face as she uttered those words.
"But I know how powerful and terrifying he is... For a thousand years, only Tsugikuni Yoriichi had the ability to kill him, but in the end, he still escaped, just by a hair's breadth."
Tamayo's heart was full of helplessness and fury, knowing there was nothing she could do.
According to Riezel's understanding of the original work, the reason why Tamayo became a demon was entirely because she was deceived by Muzan. Because of him, she killed her own husband and children, falling into eternal guilt and pain.
It was precisely this guilt and pain that gave birth to her hatred for Muzan.
Needless to say, Tamayo was right in saying that she really wanted to kill Muzan. For Yoriichi's failure to kill Muzan, she was so regretful that she could bite her lips until they bled.
"After Muzan fled, weakened due to the heavy damage he suffered, his control over me weakened as well. I managed to break free from his control and gain my freedom. At the same time, Tsugikuni Yoriichi spared me and entrusted me with assisting humans in defeating Muzan, and demons he couldn't defeat."
Tamayo lifted her head and looked at Riezel's eyes.
"Given those circumstances, can you understand my feelings when I heard the name 'Tsugikuni Yoriichi' from Tanjirou?"
Did she even need to say it? She was absolutely shocked!
She was so shaken upon learning that a swordsman named Tsugikuni Yoriichi suddenly appeared and easily killed the Upper Three. Her emotions must have been incredibly complex and intense as she heard the news.
This was why she decided to come here, to find Riezel.
"Before coming here, I couldn't help but hope, hope that Tsugikuni Yoriichi was really still alive, even though I knew it was unrealistic..." Tamayo said with a bitter smile. "Until I saw you, I felt like maybe... just maybe, I could continue to hope..."
"Oh?" Riezel said calmly. "Why do you say that?"
"Because I know you're very powerful." Tamayo answered with a firm tone, staring at him intensely. "When I first saw you, I almost thought I was seeing Tsugikuni Yoriichi himself."
Ever since mastering the Selfless State, Riezel had been able to effortlessly conceal his fighting spirit and aura. This meant that to others, he appeared to be just an ordinary swordsman, with almost no presence whatsoever.
However, that was precisely where the problem lay.
Could a swordsman capable of easily defeating the Upper Three really be someone who seemed so unremarkable, so ordinary?
Of course not!
Someone like Riezel, Tamayo had seen once before, hundreds of years ago.
Yes, it was Tsugikuni Yoriichi.
The first time Tamayo saw Yoriichi, he gave her the same impression as Riezel did now—completely unremarkable, utterly ordinary, devoid of any aura. Yet, it was precisely this unremarkable, utterly ordinary swordsman who dealt a devastating blow to Muzan in an instant.
Since then, the figure of Yoriichi has left a deep impression on Tamayo's heart.
And now, the figure of Riezel at this moment completely overlapped with the figure of Yoriichi in Tamayo's mind.
Just this alone made her unable to help but feel hopeful.
"You might be able to fulfill Tsugikuni Yoriichi's will, to slay that monster once and for all." Tamayo stated with a strong determination.
Riezel could hear the anticipation in her words, as well as a strong sense of hatred and determination.
Her determination, he had seen it in someone else before.
Ubuyashiki Kagaya, the Master of the Demon Slayer Corps and the current head of the Ubuyashiki family, had shown a similar barely perceptible determination when he spoke before Riezel, declaring his intention to end the millennia-long history of conflict between demons and humans.
Kibutsuji Muzan, the Demon King born in the Heian period, had caused too many tragedies.
Every demon was born from his hands, so for every demon that existed, there was a corresponding tragedy. Likewise, the tragedies caused by the killings and man-eating committed by these demons could ultimately be traced back to Muzan himself.
To completely eliminate demons, rid the world of man-eating monsters, ensure that the night was no longer ruled by demons, and make sure humans no longer feared the night or died because of demon brutality, it was necessary to eliminate Muzan.
As long as Muzan perished, then all demons in this world would disappear.
After all, all the demons in this world were transformed from humans by Muzan's blood, including the demon kept in the wooden box that Tanjirou always carried with him.
Whether it was Tamayo, Kagaya, or even all the Demon Slayers, including Tanjirou, the Hashira, and all the people who lost their families and suffered because of demons, they all hoped that Muzan would be eliminated.
Muzan was the one whom the Demon Slayer Corps was willing to sacrifice everything to eliminate, even if it meant gambling with everyone's lives. No one in the Corps would hesitate about this.
"Since you also go by the name Tsugikuni Yoriichi, then regardless, you must have deep ties with him." Tamayo began faintly.
Riezel remained silent for a while before responding.
"I just received a gift and a message from him..."
"What?" Tamayo froze.
"He said, I'll leave it to you..." Riezel added calmly, looking directly at her eyes.
Upon hearing that, Tamayo was stunned for a long while.
"Lady Tamayo."
Seeing Tamayo's reaction, Yushirou couldn't help but worry as he called out to her, giving Riezel a puzzled glare.
"I'm fine..." Tamayo shook her head, lowering it slightly as if wiping something from her eye corner.
But in the next moment, she suddenly said something surprising.
"Besides wanting to see Your Excellency and confirm some things, I also want to tell you two things... the Upper Three, Akaza, might not be dead."
"What?"
It was Riezel who was stunned this time.
'Akaza... not dead?' Riezel narrowed his eyes.
"It's true." Tamayo nodded solemnly. "To be honest, I've been trying to find a way to study Muzan's blood, to create a medicine that can turn demons into humans. So I've been closely watching demons with strong traces of his blood, intending to collect their blood."
Riezel was aware of this matter as well.
He knew that Tanjirou had accepted Tamayo's commission and promised to help her collect demon blood.
Of course, their top priority target was naturally the members of the Twelve Kizuki.
"I've also been closely monitoring Upper Three Akaza. During the Mugen Train's incident, Tanjirou wanted to collect his blood, but couldn't find his corpse."
"He thought he hadn't made it in time, and Akaza's corpse had already disappeared. After all, demons beheaded by Nichirin Swords usually disintegrate to ash."
"But… When I calculated the time Tanjirou gave, demons of Akaza's caliber don't turn to ash that quickly."
Tamayo explained to Riezel why she thought Akaza might not be dead.
Thanks to her, Riezel soon remembered that not all demons died after being beheaded by Nichirin Swords.
However, just as Riezel remembered this, a loud noise suddenly rang out.