[To Oyakata-sama, After much deliberation, and with her consent, I have decided to write and inform you of this matter.
As you know, since the beginning of this year, my wife's health has steadily declined. I sought out many physicians, yet each visit ended only in renewed despair.
Never before have I felt such an urgent desire to save someone, nor have I ever felt the hands that grip my sword to be so powerless.
When I invited Hiru to examine my wife, my heart was already close to despair. Yet he identified her condition and introduced me to a highly skilled physician.
That physician told me she could treat my wife's illness. In that moment, the weight that had pressed upon me for so long finally collapsed.
Her medical skill was exceptional. Under her treatment, an illness that had shown no improvement despite repeated prescriptions from other doctors finally began to turn for the better.
My wife's health gradually recovered. By May of this year, she was no longer coughing up blood frequently. By August, the symptom had disappeared entirely, and she no longer needed to survive on minimal liquid nourishment. I am deeply grateful to her.
However, that does not change the fact that she is a demon, nor the fact that I, as a Hashira, accepted her help.
During the six months she treated my wife, I observed her closely. Just as Hiru said, she does not need to consume humans—only a small amount of human blood to survive.
I felt myself waver.
I know this wavering should not exist. Yet as time passed, I found myself unable to regard her as the man-eating demon I once believed all demons to be.
Thus, as the next Hashira Meeting approaches, I write this letter to you after seeking her consent.
I await your guidance on the path forward. Rengoku]
After a long silence, Ubuyashiki opened the second letter.
[To the Head of the Demon Slayer Corps, Good day, Mr. Ubuyashiki.
I am Tamayo.
I believe Rengoku has already informed you of my existence, so I will not elaborate further.
I do not ask for your trust, nor do I seek to deny the sins I have committed in the past. I only ask that you postpone my execution until after the final battle with Muzan. At the very least, I wish to witness his death with my own eyes. Tamayo
P.S. Enclosed are various medicinal formulas I have developed over many years of research. I hope they will be of some use.]
Ubuyashiki gazed at the stack of prescriptions—nearly half a finger thick—then sighed and picked up the third letter.
[To Ubuyashiki, Whether my brother and I can eventually return to being human—or even be allowed to die—depends entirely on her. So don't touch her.
Please handle the explanation with Rengoku. Hiru
P.S. Also, please don't tell my brother yet.]
Ubuyashiki took a sip of his medicinal tea, set the letter aside, and opened the fourth.
[To Oyakata-sama, I have received Rengoku's letter.
I sincerely apologize for the trouble my younger brother has caused you yet again.
However, Miss Tamayo is a demon who overcame her desire to eat humans through her own will. She truly despises Muzan and possesses the potential to fight alongside the Demon Slayer Corps as an ally. I therefore ask that you show her special leniency.
Once again, I apologize for the inconvenience caused by my brother. After this Hashira Meeting, I will discipline him properly. Tsugikuni Yoriichi
P.S. Enclosed are my first and second compilations of sword technique insights.
The first compilation is suitable for swordsmen with an existing foundation. The second is more appropriate for beginners.
You may distribute them among the Demon Slayer Corps as you see fit. They should prove beneficial.]
Ubuyashiki set the letters down and lifted his teacup once more.
After a long silence, he instructed the Kakushi to summon Mikazuki and handed the medicinal formulas to him.
He then had Mikazuki evaluate the sword technique notes, ultimately dividing them into six volumes: the Hashira would receive the full set, the trainers would receive the complete second compilation, and the remaining volumes would be distributed according to swordsman rank.
Once everything was arranged, Ubuyashiki personally visited Rengoku.
Seeing that the former Flame Hashira had truly regained his spirit, he felt slightly reassured.
"Oyakata-sama, regarding Physician Tamayo…"
"I already know," Ubuyashiki said with a slight nod. "Treat her the same way you treat Hiru. However, this matter must remain concealed for now.
"After all, not every Hashira has lived alongside demons as you have. Without time to accumulate, trust is difficult to establish."
"…You are not blaming me for betraying the Demon Slayer Corps' principles?"
"The Demon Slayer Corps has only ever had one principle," Ubuyashiki replied, looking at Rengoku.
"To slay Kibutsuji Muzan. Until that moment arrives, I intend to unite every force that might be useful."
Rengoku remained silent for a long time.
"…Understood. I will ensure both concealment and surveillance."
"Thank you, Rengoku."
"But please give Hiru the necessary admonishment," Rengoku said with a sigh. "How can he place his trust in a demon?
"My own case could be explained away as wavering convictions, resignation, or making a deal with a demon for my family's sake. I am already a useless man—whatever people say about me does not matter.
"But he is young and full of promise. There's no reason for him to let rumors and slander shake his resolve."
"Rengoku, denying your own worth is not a virtue befitting a swordsman," Ubuyashiki Kagaya said gently. "As for Hiru… he is far more resolute than you think.
"And besides, someone will discipline him."
"You mean Yoriichi?"
Ubuyashiki Kagaya nodded with a smile.
"The Hashira Meeting is about to begin, so I cannot stay longer. Please take care of your health—and convey my regards to Miss Tamayo."
"Yes. I'll see you out."
…
Uzui felt as though he had seen a ghost.
As usual, he arrived at the Demon Slayer Corps headquarters and greeted the cute, well-mannered new recruits.
But—but—why was that notoriously brother-obsessed Sun Hashira openly lecturing his younger brother?
And judging by Hiru's dust-covered, miserable appearance, he had clearly already been through one round of scolding. So what, exactly, was Yoriichi still angry about?
[Damn it… this curiosity of mine is impossible to suppress.]
Unable to resist, Uzui crept closer.
"I know I was wrong. Next time, I'll definitely discuss it with my brother beforehand."
"Recognizing your mistakes is good. Still, I'll apply to accompany you on patrol this year."
"Eh? B-but—"
"Hiru, your weapon training also needs serious work. It's precisely because you keep avoiding training that you caused this trouble."
"But I—"
"Is Hiru already tired of his brother?"
"No! Absolutely not! But I really—"
"…I see. So you've reached the age where you no longer need your brother."
"I get it! I really get it! Let's go together! I'll train properly!"
Uzui felt even more convinced he was witnessing something unnatural.
Incomprehensible.
Truly incomprehensible.