A dilapidated and abandoned shrine by the riverside, weathered by the storms of time. A place that could now be called a deserted shack rather than a shrine.
The meaning as a shrine had vanished, and where hunters would once stay briefly to take shelter from the rain, a strange heat now lingered.
Inside the shack, the faint blue flames Kiyohime had kindled illuminated the interior instead of charcoal from a hearth. Under that light, I finally began to ruminate on my eventful fate.
Gasping for my rough breath, I looked at Kiyohime sitting before me, gazing at me with rapture.
My soul was already seasoned, even a bit weary. I had lived and died as a working adult in my early 30s in my previous life, was reborn and lived over a decade as a peasant in the Meiji era, and lived about 20 years as an oni.
In total, it was a soul that had endured over 60 years. But the moment I became an oni, my body's time stopped. In the mirror remained the appearance of a teenage boy who hadn't quite shed his youthful look, but behind those eyes crouched the self of a middle-aged man who had been through all kinds of hardships.
This strange sense of disparity became even more pronounced in the face of Kiyohime's unrestrained affectionate assault.
"Master, what are you thinking so deeply about? By any chance... am I lacking? Or is my flame too hot, putting a strain on your cold body?"
Kiyohime whispered as she slyly climbed onto my lap. Her serpentine, flexible arms wrapped around and embraced my neck. Instead of refusing, I wrapped my arms tightly around her slender waist.
The experience of 60 years of life advised me not to act so foolishly as to kick away fortune that had come seeking me.
"No, of course not. It's just that you are so beautiful, and I'm afraid this unrealistic situation might vanish like a fleeting dream."
At my honest and seasoned reply, her eyes instantly shimmered into heart shapes and her face flushed bright red. She pulled my neck tighter and pressed her lips against mine.
The night, intertwined with an oni's dramatically developed regenerative power and the dense magical energy emitted by a Servant, was long and hot.
Thanks to senses dozens of times more sensitive than when I was human, I could keenly feel that she was not a hallucination created by a mere Blood Demon Art, but a living, tangible being. Her heartbeat, the temperature of her skin, and even her plaintive voice calling me were all real.
As the hearth blazed, our bodies grew hot and we explored each other.
After the storm-like time passed, the cold dawn air began to seep through the cracks in the shack's window frame.
Slowly stroking the hair of Kiyohime, who had fallen asleep in my arms with a satisfied expression, I opened my mouth.
With her ear pressed against my chest, she opened her eyes slightly, using the irregular heartbeat of an oni as a lullaby. It was now time to teach her about the brutal order of this world upon which we stood.
"Kiyohime, let me tell you about this world I live in, and the enemies we must face."
"Wherever you are, Master, I don't care even if it's the abyss. But please tell me. Your voice is sweeter than anything else in this world."
I began my explanation calmly. I confessed that I was originally a human from another world called the modern era, that I was reincarnated and spent another 30 years as a peasant and an oni in this era. And about the tragedy of being attacked by a monster called an oni and becoming a monster myself, and about their leader, Kibutsuji Muzan.
"In this world, oni can only survive by preying on humans. But I escaped Muzan's control. I don't know the reason, though. The ones who attacked us last night are called the Demon Slayer Corps. It's an organization of humans who hunt oni. To them, I am just a monster that deserves to be killed."
Kiyohime rubbed her cheek against the back of my hand and gave me a pitiful look.
"My poor Master... How much you must have suffered. Don't worry. If it's about burning to death those humans who oppress you and offering them as your nourishment, I will help you as much as you need. And that Muzan person... I will definitely melt him away with my serpent's flames."
We left the shack before sunrise. After several days of searching, I sensed a vile, pulsating aura from a cave in the nearby mountain range. It was the presence of an oni who, while not having inherited Muzan's blood thickly, had grown somewhat strong by devouring dozens of humans.
"Kiyohime, it's in there. This time, I'll step forward first. I've grown strong enough to develop a Blood Demon Art, so I need to confirm how this Blood Demon Art can be applied, how it functions in actual combat."
"Yes, Master. But call me immediately if you're in danger. My flames are always ready to blaze for you."
I darted into the cave under cover of darkness. Deep inside the cave, a grotesque oni with a massive body and multiple arms was tearing apart and eating rotting corpses. It spotted me and laughed, baring its yellow teeth.
"Hehe... What's this brat of an oni? The price for stepping into my territory is your life!"
The creature charged at me, swinging its many arms. I calmly awakened the sensations from my past life. The years I had lived as an oni taught me how to minimize unnecessary movement. I evaded its attacks by a hair's breadth and extended my hand.
"Blood Demon Art, ."
As I flicked my finger and activated the Blood Demon Art, Kiyohime was summoned into the void along with a crimson blood-red hue. My intention now was to call her and no one else, and Kiyohime properly moved to stand before me. She spun gracefully in the air and unfurled her fan.
"How dare you bare your fangs at my Master with such audacity! You vulgar insect!"
With Kiyohime's shout, blue flames filled the cave. The oni screamed and staggered back, but the flames were completely paralyzing its regenerative power.
Seeing the flesh touched by the flames turn black and charred without regenerating, I became certain. It's not just simple firepower. Kiyohime's mystery was surpassing the oni's recovery. Perhaps because it's the flame of a serpent-dragon, a being superior to oni? At any rate, it's at least not a special flame like Nezuko's.
I seized the back of the creature's neck as it writhed in pain. And something, an instinctual force, surged within my body. The faint trace of Muzan's blood within the creature, and the life force it had accumulated, began to be sucked into me through my palm.
"G-g-gah!"
Crrrack!!!
The oni's body instantly withered and twisted like a mummy. And I felt a sensation of something entering my body.
Is this... absorption? Drain?
My Blood Demon Art isn't just about summoning; can it also strengthen my power by using the essence of the enemies I defeat as nourishment? Oni grow stronger by eating humans or by receiving Muzan's blood. Is this a similar concept?
"Master, that's amazing! That stance just now, you were so strong and cool!"
The inside of the cave was eerily flickering from Kiyohime's blue flames. The oni withered in my grasp crumbled, and the crumbling oni's remains turned to dust and scattered. Instead, the blood flowing through my veins began to carry a heat much denser and hotter than before.
Even a seasoned spirit that had lived 60 years couldn't help but shudder at this sudden expansion of power. I looked down at my palm and murmured quietly.
"This isn't simple predation. It's the power to take, to seize, to make it mine... Though it doesn't feel like it would give me a new Blood Demon Art. Maybe it just steals physical power."
Oni grow stronger the more of Muzan's blood they receive. This must be a similar case.
I decided to give this bizarre yet fascinating power a name.
"Blood Demon Art, ."
Vitality overflowed within my body.
"Ahh, Master... That name is truly splendid. A declaration that you would place even the powers of the underworld beneath your feet? As expected of the one and only man I chose."
Kiyohime softly embraced me from behind. Her ample bosom and hot body temperature touched my back, but I was now more focused on the changes occurring within my body than on that temptation.
The life force of the oni I just absorbed. Could it perhaps strengthen my Blood Demon Art to allow me to summon heroic spirits other than Kiyohime?
"With this, I'm becoming a demon hunter in a different sense, huh. What I need to do is roughly clear now."
"What do you plan to do now?"
"For now, I'll wander as I have been, but I'll settle somewhere. I need to establish an identity as a human and build a foundation to live on. Well, I can only eat humans."
"Then I'll try making dishes based on human flesh!"
"Ah, sure."
So she really is Chaotic Evil, huh. Offering to cook human flesh so casually. Is this also the attitude of a good wife and wise mother, or is it madness?
At the very least, I need to train my power for a while. Honestly, with just me and Kiyohime as we are now, it would get difficult from around the Upper Ranks. Kiyohime is formidable in terms of flame output or her ability to fight as a fire dragon, but she is among the weaker ones.
I think we could win against Gyutaro or Gyokko, even Hantengu. From Akaza onward, I'm not confident. Actually, I feel like I'd die first. Especially Kokushibo is a powerhouse who could definitely kill Kiyohime and more.
Unless it's another heroic spirit, with a weaker-class Servant, even fighting the Upper Ranks is hard to guarantee victory. Honestly, even the lower-ranked Upper Moons would be tough to beat.
For now, let's hunt weaker oni and build our strength. And while doing that, let's try summoning other heroic spirits. I have a feeling it'll be difficult to summon anyone other than Kiyohime right now. Honestly, I think my current power itself is around the level of a Swamp Demon.