Perfect 1

Sarutobi Hiruzen watched the death-row prisoner before him with anticipation.

He had little regard for so-called demons, but if this really was a Perfect Being—immortal, unafraid of sunlight, and able to survive without eating people—even Sarutobi Hiruzen would be tempted.

And, just as expected, a wondrous transformation began in the prisoner before him.

The Blue Spider Lily and the Demon King's blood had produced an extraordinarily mysterious reaction.

Sarutobi Hiruzen sensed a presence that was neither wholly human nor wholly inhuman emanating from the prisoner.

The body, which had been ordinary and worn, began to writhe slowly. Its rough skin underwent a fresh cycle of renewal, growing fair and resilient.

"Clang!"

Suddenly, the experimental subject's eyes flew open. He broke free of some of the Sealing Jutsu restraining him and slowly rose to his feet.

Sarutobi Hiruzen sized up the subject. There was no doubt that this man had completely evolved into a species more advanced than either demons or humans.

"Splash."

A stream of purple liquid suddenly appeared and struck the subject, soaking his upper body. But he remained motionless, seemingly unconcerned.

"So Wisteria has no effect on him anymore."

Sarutobi Hiruzen nodded. The concentrated extract made from numerous Wisteria flowers was the Demon Slayer Corps' main weapon against demons.

Even Kibutsuji Muzan, though unafraid of it, showed a distinct aversion.

But this Perfect Being showed no reaction at all. He had evidently overcome Wisteria's effects completely.

Sarutobi Hiruzen flipped one hand, and a crimson short sword appeared in it.

In the dim basement, the crimson blade gave off a light like the sun.

"A weapon forged from Scarlet Crimson Iron..."

"It's also known as a Nichirin Sword."

Sarutobi Hiruzen weighed the Nichirin Sword in his hand. It was a fine weapon, one this era had never seen before.

It was also one of the reasons he had left the Demon Slayer Corps and come down from the mountain.

"Even if I don't need it in this world, I might run into troublesome creatures like Dracula in another."

Scarlet Crimson Iron was found only atop high mountains. Sarutobi Hiruzen had secretly taken quite a bit of it, collecting a local specialty from this world.

"Clang!"

A flash of steel streaked through the dim basement.

Without hesitation, Sarutobi Hiruzen swung the short sword forged from Scarlet Crimson Iron and slashed the experimental subject.

The blade sank into flesh. Sarutobi Hiruzen silently assessed the feel of the cut.

"It doesn't feel like human skin."

"After evolving, his skin is tougher—more like cowhide..."

"His physical abilities are just as impressive as a demon's..."

"And he's completely free of the weakness demons have to Nichirin Swords..."

Sarutobi Hiruzen watched the wound on the subject's body heal rapidly, without the slightest impediment.

"Then there's only one last step."

With ease, Sarutobi Hiruzen lifted the weight of a grown man and carried the subject straight outside, into the sunlight.

"SSSS!"

Like fresh snow beneath the sun, the subject's body began to melt away. It seemed he had overcome the weaknesses to Nichirin Swords and Wisteria, but the sun's power was still too much for him.

Sarutobi Hiruzen didn't rush. He simply waited.

Sure enough, after sunlight had melted half the subject's body, a sudden change occurred.

Some mechanism in the subject's body seemed to activate. The sun's effect on him rapidly diminished.

The melting slowed as well. In just a few dozen seconds, the subject overcame his weakness to sunlight.

Watching the subject stand beneath the sun, Sarutobi Hiruzen nodded with satisfaction, then shook his head.

"It's just a shame..."

Sarutobi Hiruzen considered the experiment a success, but not a complete one.

After finishing his evolution, the subject had simply sat there, dazed.

Though conscious, he ignored Sarutobi Hiruzen's attacks. Even as the sunlight ravaged him, he showed no reaction.

"He's lost his mind?"

Seeing this, Sarutobi Hiruzen knew the subject had fallen into the same state Nezuko had during her evolution—and perhaps an even worse one.

Nezuko's family had passed down the practice of Sun Breathing, which had transformed her body.

But the subject before him seemed to have lost even his basic instincts. He was no different from a person in a vegetative state.

As for whether he could recover...

Sarutobi Hiruzen wasn't about to gamble on it, though the protagonist could.

The protagonist had been able to regain his sanity thanks to many factors, including luck, emotions, Breathing Style, and bloodline.

"In any case, until this flaw is completely resolved..."

Sarutobi Hiruzen shook his head.

"I can't risk tampering with the demon bloodline."

"Even if he can recover..."

"There's no guarantee nothing will go wrong during that long period when his mind is unclear."

Sarutobi Hiruzen didn't want to entrust his life to someone else.

"And even if he does recover..."

"Will the new species retain the person's old personality..."

"Or will it have an entirely new soul?"

"There's no way to know."

Sarutobi Hiruzen studied the world's first Perfect Being.

He decided to name him Perfect 1.

"But even so..."

"This experimental subject is enormously significant..."

"After all, going from zero to one is entirely different from going from one to a hundred..."

"Now that the process of creating a Perfect Being has taken us from zero to one..."

"Developing a way to graft the Perfect Being's bloodline without side effects is only a matter of time."

"By then, I may have found an even better way to solve the problem of lifespan..."

Sarutobi Hiruzen sealed Perfect 1 once more.

"Besides, compared with Ninja methods..."

"Even a corpse can be used to kill. A Biological Weapon this perfect is all the more useful."

An immortal body, limbs capable of Thousand Transformations, physical abilities far beyond an ordinary person, potential for further evolution, and a remarkably stable genetic structure.

In Sarutobi Hiruzen's eyes, he was a perfect Biological Weapon.

Far superior to something like the T-Virus.

At the Ubuyashiki Clan's estate,

the Ubuyashiki Clan Head was discussing Demon Slayer Corps matters with Tsugikuni Yoriichi.

Sarutobi Hiruzen arrived without warning.

"Lord Sarutobi..."

The Ubuyashiki Clan Head remained as warm and friendly as ever.

"It's wonderful that you're here."

"Most of the Demon Slayer Corps members have now learned a Breathing Style."

"At last, we have the means to fight the demons."

"Some swordsmen can now slay demons on their own..."

"So Yoriichi and I were discussing how to purge the demons from Kyoto."

"It would be wonderful if you could join us."

Sarutobi Hiruzen replied,

"Purging them will be difficult. The Demon Slayer Corps has only just learned Breathing Styles, and their combat strength is still limited..."

"It would be better to hone your skills first."

"As for the many demons who prey on people..."

"Once Demon King Muzan is killed, the rest of the demons will perish on their own..."

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