Chapter 209: Tamayo's Breakthrough
Life gradually settled back into a familiar rhythm. For Akira, the days blurred into a steady cycle of rigorous training, routine patrols, and relentless stakeouts aimed at hunting down Douma.
Unfortunately, the elusive Upper Rank Two was nowhere to be found. Left with no other options, Akira had to settle for snatching up a random, low-level demon off the streets just to keep the drug testing.
Ever since Akaza's demise, demonic activity across the outside world had plummeted drastically. Merely tracking down a single demon to serve as a test subject now required a frustrating amount of effort.
'Annoying,' Akira thought, his patience wearing thin.
To make matters worse, his surveillance revealed that Douma had not returned to the Eternal Paradise Cult in quite some time.
'Extremely annoying.'If he had to guess, the flamboyant demon was likely being worked to the bone by a highly unreasonable boss. Perhaps the'Mu'in Muzan actually stood for'mercilessly overworking your subordinates.' Akira could only shake his head and let the matter rest for now.
While the hunt for Douma had hit a dead end, the world of pharmaceutical research had yielded a monumental victory. Tamayo had finally produced a result worthy of immense celebration.
On this particular day, every single Hashira of the Demon Slayer Corps gathered together outside the Ubuyashiki Estate. They were not there for a strategy meeting, but to bear witness to an experiment that would forever alter the history of the Corps—the complete reversal of demonization.
The demonstration took place deep within Tamayo's underground laboratory. The air was thick with anticipation. Shinobu stood by with a clipboard, acting as the lead recorder, while Tamayo prepared the medical instruments. Yushiro hovered nearby, carefully handling the material preparations.
The brave volunteer receiving the injection was none other than Chachamaru.
Naturally, the serum entering the calico cat's veins had already undergone countless experimental refinements. Its core feasibility had been thoroughly verified. Today's gathering was simply to allow the Hashira to see with their own eyes that a genuine cure to turn demons back into humans had been perfected.
As for the demons used in the earlier, less refined trials... those unfortunate enough to experience a failed experiment were casually dispatched by Akira with a single, effortless slash.
Even the very first successful case had not required much finesse. Whenever Akira conducted field tests, he simply used whatever environment was available. He would pin the struggling demon to the dirt, completely restricting its movements, and cleanly pierce its vocal cords to prevent any obnoxious screaming.
The result of that particular test was a complete medical success, leaving behind a perfectly human corpse. Regardless of the outcome, they were all man-eating monsters. Even if they reverted to humanity, their past atrocities could not be washed away. Death was a fitting end.
Originally, Tamayo had desperately hoped to use the finalized cure on Yushiro. Decades ago, when she transformed the terminally ill boy into a demon to save his life, she had sworn to one day return his humanity. Yet, because Tamayo refused to take the cure herself, Yushiro adamantly rejected the offer. It was the very first time he had ever so fiercely defied her wishes.
Tamayo's reasoning was rooted in her own guilt. She believed she carried the weight of unforgivable sins and had no right to live out the rest of her days as a normal human woman. also, by retaining her demonic physique, she could actively contribute to the inevitable final battle against Muzan. Reverting to a fragile human state would strip her of her combat utility and render her a liability on the battlefield.
Since Tamayo refused the cure, and Yushiro would rather die than abandon her in her demonic state, their collective gaze eventually fell upon Chachamaru.
In the past, the loyal cat had voluntarily accepted demonification simply to provide Tamayo with eternal companionship. Now that she needed a living subject to prove her life's work, Chachamaru was more than happy to return to being an ordinary feline.
Under the intense, unblinking stares of the gathered Hashira, as well as Amane—who had come to witness the miracle on behalf of her mobility-impaired husband, Kagaya—Tamayo calmly administered the serum. Chachamaru did not fuss, accepting the needle with complete cooperation.
Moments later, the cat slipped into a deep slumber.
Everyone in the underground room stared intently at the sleeping creature, subconsciously holding their breath. The silence was heavy. Second after second ticked by, and at first, the feline appeared entirely unchanged.
Slowly, however, the atmosphere shifted. Everyone present possessed keen senses, and they could all feel the cold, eerie aura inherent to all demons steadily dissipating from Chachamaru's small body. The process was gradual, yet incredibly smooth. The unnaturally sharp claws, which had grown far deadlier than a normal cat's due to the demonic blood, began to retract bit by bit into soft paws. The faint, elongated fangs completely receded, hiding themselves harmlessly behind its lips.
An indeterminate amount of time passed before Chachamaru finally stirred. The cat slowly opened its eyes, letting out a soft, somewhat lazy meow.
Under the collective gaze of the strongest swordsmen in the world, the calico stretched its small body, arching its back before hopping directly into Tamayo's familiar embrace.
It was a well-known fact that normal cats despised cold surfaces, and Tamayo's demonic body lacked the warmth of human blood. Yet, upon waking as a mortal creature once more, Chachamaru still sought out her arms. It was a beautiful confirmation that the cat retained all of its past memories and its deep affection for its master.
Seeing the feline snuggled so intimately against Tamayo's chest, Yushiro's jealousy ignited like a powder keg. He opened his mouth to scold the animal, but before a single word could escape, the Hashira had already surged forward, crowding around Tamayo to get a closer look.
Pushed to the periphery, Yushiro's irritation spiked. He wanted to lash out in a fit of rage... but his anger fizzled out almost instantly.
'What else can I even do?'Yushiro thought, swallowing nervously.'Every single person in this room, except for that white-haired woman, could decapitate me with a casual wave of their hand.'
Unsurprisingly, absolutely no one paid any mind to Yushiro's internal crisis.
Feeling the genuine, radiating warmth of a living creature in her arms—a heat akin to a small hand warmer—Tamayo already knew the answer. Still, for the sake of absolute scientific rigor, she and Shinobu conducted a complete series of medical examinations on Chachamaru. The results were absolute. The feline had successfully transitioned from a demon back into a perfectly normal cat.
Upon hearing the final confirmation, genuine smiles broke out across the room. Even Akira, who had ruthlessly orchestrated the very first lethal success, wore a look of quiet satisfaction.
With a viable cure finally in their possession, the Demon Slayer Corps had unlocked an unmatched tactical advantage. Tamayo had long since mastered the medical procedure to turn humans into demons. By combining these two breakthroughs, a revolutionary concept emerged: anyone suffering from a fatal, incurable injury could theoretically be saved by first being transformed into a demon to heal, and then immediately injected with the cure to restore their humanity.
Even if this radical idea remained purely theoretical for now, the medical feasibility was incredibly high.
"You have created a true miracle, Lady Tamayo."
Amane Ubuyashiki stepped forward, bowing deeply and solemnly toward the demon physician.
"This is not my achievement alone," Tamayo replied softly, hurriedly stepping aside to avoid accepting the full weight of the bow.
While she had led the research and development, she knew she could not have succeeded without the tireless assistance of the Kochou sisters and Yushiro. The endless stacks of field-test data provided by Akira had been equally indispensable. Additionally, the rapid breakthrough was only made possible by the incredibly potent blood samples Akira had harvested from the Upper Ranks, combined with the Lower Rank blood gathered by the other Hashira.
Beyond the physical materials, the staggering financial backing of the Ubuyashiki family had kept the project afloat. Since Tamayo had aligned herself with the Corps, she had developed numerous life-saving drugs, but the cost of the rare materials required was astronomical. Even with the small fortune she had quietly amassed over several centuries, Tamayo frequently found herself shocked by the sheer amount of capital they had burned through over the past two years.
Most of all, Tamayo felt a deep sense of gratitude toward Akira and Kanae, who had staked their reputations to vouch for her inclusion in the Corps. She also thought of the Kamado family, who had willingly risked their own safety to prove that she and Yushiro meant no harm.
Without their unwavering trust, none of today's triumphs would exist.
Now, it seemed she finally possessed the means to repay that monumental kindness.
Tamayo lowered her gaze, her mind racing with medical possibilities. As an experienced healer, she had observed Tanjuro Kamado from afar. Even without a formal examination, she could clearly see that the man's life force was severely overdrawn. His frail body would not hold out for many more years.
But with the demon-to-human cure now a reality, that highly theoretical, extreme medical procedure became a viable option to save his life. The only hurdle remaining was Tanjuro's own consent. After all, not every human possessed the mental fortitude to accept becoming a flesh-eating monster, even if it was only a temporary measure meant to heal a dying body.
Ironically enough, a certain progenitor of demons could relate to that exact hesitation.
Centuries ago, it was precisely because Muzan could not patiently endure his own agonizing medical treatment that he murdered his doctor, inadvertently setting this entire, blood-soaked history into motion.
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