Three months had already passed since coming to Tokyo. Akatsuki Trading Company's Store 2 had successfully settled in Taki-no-Gawa, and profits from various businesses including instant ramen were breaking records every month.
Wealth had accumulated, and the nightly sex with the heroic spirits was sweet. But one corner of my heart was coiled with an indescribable regret.
"Hoo..."
The headquarters study, thick with darkness. I opened and closed my palm, checking the sensation. My Blood Demon Art was becoming more sophisticated daily. Now I could finely sense the life force around me without even concentrating. But the problem was my body.
"The growth is slow."
It hasn't even been 30 years since becoming an oni. Compared to the hundreds of years Muzan or the Upper Moons have lived, my age is no different from a child's.
But perhaps because I retain a human soul. I found it hard to endure this plateau. Doma is an ability-type who fights mainly with Blood Demon Arts, but he possessed a robust physical durability and reaction speed matching the power of his Blood Demon Arts.
In other words, rather than being like Akaza or Kokushibo who heavily invested in physical power, I should be like Doma—having strong abilities while also possessing physical abilities matching that level.
Despite sparring every night and hunting and devouring nasty humans and nameless oni, my strength and regeneration speed seemed to have stopped at some point.
"Lord~ Worrying again? Wrinkles are forming between your brows."
Shuten Douji, who had approached unnoticed, leaned moistly against my shoulder and offered a sake cup.
"Shuten, for humans generally, the method of getting stronger or visible growth is intuitive. But I... feel like this body isn't keeping up with my will. My Blood Demon Art pours out like a waterfall, but the container holding it is too small."
"Hmm, is that so. An oni is an oni, but demons are different from oni, so it's hard for me to advise. What's certain is we're beings living through eternal time. Time is the medicine, but our Master is too impatient. Is it because you still have human-era sensations? It takes enduring hundreds of years to become a true Demon King."
Even Shuten's consolation didn't quench the thirst. The decisive battle with Muzan is less than 10 years away. The thought that with my current physical abilities, I can't keep up with that monster's speed. I think I need to be at least Upper Moon level, Akaza level. The problem is my greed is excessive.
My oni talent isn't as outstanding as Doma's, nor was I a superhuman like Kokushibo or Akaza even as a human. If only I could acquire physical abilities, it would be perfect.
Deformed growth relying only on Blood Demon Art will eventually hit a limit. Doesn't even Doma possess transcendent physical abilities supporting his overwhelming ice Blood Demon Art?
I was still trapped in human time perception, unable to accept the oni's eternity. I need Muzan's blood after all. Should I hunt the Twelve Kizuki, the Lower Moons? I could target Upper Moons too, but compared to Lower Moons whom Muzan doesn't care much about, Upper Moons are those he values specially. In their own way.
The time I suddenly grew dramatically was five years ago when I absorbed Lower Moon Six. The difference between the Twelve Kizuki and ordinary oni is vast. That's when I summoned Tamamo. That was the only time I grew dramatically in a short period.
I need to accelerate Lower Moon hunting after all. I have to eat them before the Demon Slayer Corps catches them. Time is truly cruel.
Another concern was the Kocho family. After starting interactions near Store 2, using medicinal ingredient trade as an excuse, I had grown quite close to them.
Kanae's affectionate smile and Shinobu's sharp yet polite attitude became a small sanctuary in my desolate oni life.
But I knew. According to the original flow, they were supposed to be attacked by an oni and lose their parents.
"Butterfly effect..."
The very fact that I established a trading company in Tokyo and set up a base in Taki-no-Gawa was already twisting history. If I protect them, Shinobu won't join the Demon Slayer Corps, and the poison that could even kill Upper Moons, and the medicine that could weaken Muzan might not be born.
That could lead to humanity's defeat—a dangerous gamble. Of course, even without that, I can kill Muzan, but if there's something that weakens him, it becomes easier. Rather than just killing, it would be good if there was a way to absorb Muzan instead.
Gaining Muzan's tremendous life force. If I become human, everyone disappears. In the end, living as an oni is best for me. I'll modify my body to increase human-like aspects and live through eternal years.
I used to want to live like a human, but now I don't want to part with everyone, so I want to live as an oni. Blue Spider Lily or eating Muzan. There's a lot to think about.
Well, let's focus on the Kocho family for now.
Let them die by an oni as they were. The Kocho parents need to die for the girls to become Demon Slayers. That would be good for me too.
Remembering Shinobu's bright pouting during the day made me weak-hearted.
"Akira-san! I'll go get this herb myself, so please talk to my sister! She keeps treating me like a kid!"
To have to stand by and watch that spirited girl end up wailing in a pool of blood.
"Tamamo?"
"Yes, Master. My familiars are hiding under the Kocho family's roof and throughout the yard. I've also fixed spells so transfer magecraft can be activated immediately if something happens."
Tamamo, as if reading my complicated feelings, softly covered the back of my hand.
I assumed scenarios up to situations where Himejima Gyomei or the Demon Slayer Corps might not come. In that case, I'd have to save them myself. If no oni attacks, should I create an attack deliberately? That's a bit too much.
Amidst such anguish, the wheel of fate began to turn.
The incident broke out a few days later, on a pitch-black night when even moonlight was hidden by clouds.
While eating the rare blood and meat I'd finally obtained, Tamamo hurriedly opened the door and entered. Her pupils were shaking urgently.
"Master! The spells reacted! An oni has invaded the Kocho house!"
"The Demon Slayer Corps?"
"No signs at all around! The Kocho parents will die soon, I think!"
So it came to this after all. Even if the butterfly effect comes, it becomes troublesome like this. I immediately rose from my seat.
"Okita, Ushiwaka! Let's go!"
As Tamamo formed a complex hand seal in the air, a magic circle appeared on the floor. The sensation of my vision twisting and space folding passed instantly. When I opened my eyes, before us was not the peaceful Kocho household but a scene of hell.
"Aaaah! No! Mom! Dad!"
Young Shinobu's scream tore through the night air. The living room once full of herbal scent was now filled with a fishy blood smell.
The parents were already collapsed on the floor without movement, and above them, an oni with a grotesquely twisted body was stretching its hand toward the sisters, blood staining its mouth.
A stray demon, not even one of the Twelve Kizuki, unable to use Blood Demon Arts. But to the powerless human sisters, it was more colossal than any disaster.
"You filthy monster...!"
Ushiwakamaru dashed out with lightning speed. Her sword, Ubusumidori, emitted a cold blue light under the moonlight.
Slice!
A single slash. A strike that didn't even permit the oni's scream. Ubusumidori carried properties similar to a divine sword that pursues demons, immediately blocking the oni's regeneration just like Nichirin blades. I instantly snatched the oni's head rolling on the floor, its body bisected.
"G-guk... What are you..."
"No need for you to know."
I gripped the oni's neck and absorbed its life force. As I absorbed every last drop of the vile blood energy and vitality it possessed, the oni's body turned to dust and scattered. But there was no victorious pleasure.
"Mom... Dad... Please open your eyes..."
Kanae was sobbing, clutching her parents' blood-soaked bodies. Shinobu sat slumped beside her as if her spirit had left, trembling violently.
If I had come just a little faster, I could have saved the parents too, but I didn't even consider that option. Selfish if it's selfish, for my purpose.
I approached them, wiping my bloody hands. Okita and Ushiwakamaru scanned the yard without lowering their guard, and Tamamo looked at the sisters with pitiful eyes.
"Kanae, Shinobu."
At my voice, Kanae looked up. My reflection appeared in her eyes, smeared with tears. Not the kind trading company owner of usual, but the cold savior unable to hide his oni aura.
"Ah... Akira-san...?"
Her voice trembled weakly. Sorrow from losing parents and fear toward these beings with unknown power were mixed together.
I looked down at the parents' bodies collapsed on the floor. The original trajectory was modified, but the cost was still cruel.
Now the Demon Slayer Corps won't come. The fate of these sisters depended entirely on my hands.
What should I do with these children?
Should I take them in and raise them as members of the trading company, or send them to the Demon Slayer Corps using this tragedy as motivation after all?
Looking at Shinobu's pale face, I trembled. If her talent for making poison isn't cultivated, many things will change. Even if the result is predetermined, the process will change a lot.
But is it right to push this child trembling in my arms toward a path of death?
"Tamamo, move these children to our house first. Let them rest for now."
"Understood, Master."
I carefully picked up the terrified Shinobu. Her small, frail body trembled finely in my arms.
"Akira-san... What about our mom and dad? What happens now?"
Shinobu's small hand tightly gripped my sleeve. Unable to bring myself to answer, I held her more firmly. Rather than worry about the changed future, a strange sense of responsibility filled that place.
After moving the sisters to our house—a secluded forest dwelling far from headquarters—Tamamo put the children to sleep with magecraft. A temporary measure to free them from extreme mental shock.
"Master, what will you do with these children?"
Kiyohime asked me standing by the window. I looked up at the night sky visible outside. The ugly oni world hidden beneath the beautiful night sky. And the key that could end that world was now lying on my bed.
"Shinobu's talent... I can't abandon it. But sending her to the Demon Slayer Corps might not be the only answer. Our trading company has Tamamo, your magecraft, and many books and materials about various medicines. We might be able to educate them more efficiently and systematically than the Demon Slayer Corps."
I decided. Instead of worrying about the butterfly effect, I would create a new flow myself.
"We'll teach them. Okita's swordsmanship for Kanae, and pharmacology using the trading company's capital for Shinobu. Not in the Demon Slayer Corps, but under Akatsuki's wing, I'll raise them."
It was a dangerous choice. An oni like me teaching how to hunt oni. But for me, whose physical growth seemed to have stopped, these sisters would become another investment for the future.
"This will be interesting. The Master's disciples. I'll teach them very strictly, but lovingly."
Tamamo laughed playfully, but her eyes were also serious. Shuten Douji watched us from a corner with interest while drinking sake.
"Ooh, raising butterfly fledglings, huh. When they grow up well later, make them drinking buddies for me."
One night in 1905. The butterfly of Taki-no-Gawa fell into my arms with broken wings.
Whether this was the end of tragedy or the start of a greater storm, only the moonlight knew.
But what was clear was that this world's story had now begun to surge violently in a completely different direction from the original I knew.
It's a pity those children won't learn Breathing Styles. But I can't say it's absolutely impossible. They'll meet the Demon Slayer Corps someday. I can capture a swordsman who uses Flower Breathing. Even if not the cultivator, I can capture a swordsman who learned it and make them teach.
Tamamo can handle it with suggestion spells, and simultaneously hide them from the Demon Slayer Corps' eyes with magecraft. Make it seem like the brought Demon Slayer member simply disappeared naturally. They're just disposable pawns anyway. They're the types who send masses of ordinary members to mountains with Upper Moon Five to die meaningless deaths.
Would they notice one or two swordsmen? They're the ones who feed kids trained under cultivators to oni as food in the first place.
Ubuyashiki. Even I, an oni, feel pure evil in the Demon Slayer Corps' actions. One of the reasons I hate them is the selection exams or creating meaningless deaths.
Well, wasn't the Demon Slayer Corps' foundation telling Yoriichi, who taught Breathing and did everything for them, to commit seppuku because he let Muzan escape?
Whatever, I'll do as I please now, original story be damned. If they don't like it, they can come kill me.