Perfect 1

Sarutobi Hiruzen stared at the death row inmate before him with a hint of anticipation.

Although he looked down on so-called demons, if it were truly a Perfect Being that was immortal, unafraid of sunlight, and did not need to consume humans to sustain its life.

Even Sarutobi Hiruzen would be tempted.

And sure enough, a certain mysterious transformation began to occur in the test subject before him.

The Blue Spider Lily and the blood of the Demon King produced an incredibly profound chemical reaction.

In Sarutobi Hiruzen's perception, an aura that was neither human nor demon appeared on the body of the death row inmate.

The originally ordinary and aged body began to squirm slowly, its rough skin undergoing a brand-new metabolism, becoming fair and resilient.

"Clang!"

Suddenly, the test subject opened his eyes, actually breaking free from part of the Sealing Jutsu's restraints, and slowly stood up.

Sarutobi Hiruzen examined the test subject; there was no doubt that this guy had completely evolved into a species higher than both demons and humans.

"Hiss."

A stream of purple liquid suddenly appeared, striking the test subject and drenching his upper body, but the subject remained motionless, completely ignoring it.

"So, there is no reaction to Wisteria anymore."

Sarutobi Hiruzen nodded; the flower extract compressed from many Wisteria flowers was the Demon Slayer Corps' primary weapon against demons.

Even if Kibutsuji Muzan did not fear it, he would still show an intense aversion to it.

However, this Perfect Being before him showed no reaction at all, clearly having completely shed the weakness to Wisteria.

Immediately after, Sarutobi Hiruzen flipped his hand, and a short Scarlet Crimson Iron katana appeared in his grasp.

In the dim basement, the scarlet katana emitted a light akin to the sun.

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

"Also known as a Nichirin Sword."

Sarutobi Hiruzen weighed the Nichirin Sword in his hand; this was a good item not found in this era.

It was also one of the reasons Sarutobi Hiruzen left the Demon Slayer Corps and came down the mountain.

"Because even if it's not useful in this world, one never knows when one might encounter troublesome things like Dracula in other worlds."

Scarlet Crimson Iron only appeared on the peaks of high mountains, and Sarutobi Hiruzen had secretly taken quite a bit of it, considering it a collection of this world's specialties.

"Clang!"

In the dim basement, a flash of blade light streaked by.

The short katana made of Scarlet Crimson Iron in Sarutobi Hiruzen's hand slashed into the test subject's body without hesitation.

The sound of the blade entering flesh rang out, and Sarutobi Hiruzen secretly gauged the feel.

"It doesn't feel like human skin."

"The skin after evolution is tough, more like cowhide..."

"The physical constitution is also no less than that of a demon..."

"And it has absolutely no weakness to the Nichirin Sword like a demon does..."

Sarutobi Hiruzen watched the wounds on the test subject's body heal rapidly, showing no signs of hindrance.

"Then, only the final step remains."

Sarutobi Hiruzen easily lifted the weight of the adult man with one hand.

He dragged the test subject directly out into the sunlight.

"Sizzle!"

Just like early snow meeting the sun, the test subject's body began to melt slowly; it seemed the subject had only overcome the weaknesses of the Nichirin Sword and Wisteria.

He was still powerless against the great might of the sun.

But Sarutobi Hiruzen was not in a hurry, instead waiting quietly.

Sure enough, just as the sunlight had rapidly melted half of the test subject's body, a sudden change occurred.

It seemed to have triggered some mechanism in the test subject's body; rapidly, the effect of the sunlight on the subject began to diminish.

The melting reaction also continuously decreased, and in just a few dozen seconds, the test subject had overcome the weakness to sunlight.

Watching the test subject standing tall in the sunlight, Sarutobi Hiruzen nodded in satisfaction, yet shook his head as well.

"It is just a pity..."

Sarutobi Hiruzen noted that this experiment was a success, yet also a failure.

Because after completing the evolution, the test subject just sat there in a daze.

Even though he was conscious, he turned a blind eye to the attacks Sarutobi Hiruzen inflicted upon him; even under the ravages of the sunlight, he showed no reaction.

"Has he lost his original intelligence?"

Seeing this, Sarutobi Hiruzen knew that this test subject had fallen into the same state as Nezuko before.

That was a case of losing memory and consciousness during the evolutionary process, or perhaps even worse.

After all, the generations of Nezuko possessed bodies modified to learn Sun Breathing.

Yet the experimental subject before him seemed to have lost even basic physical instincts, making it no different from a vegetative state.

As for whether it could recover.

Sarutobi Hiruzen stated that while the protagonist could afford to gamble, he certainly could not.

Likewise, the protagonist's ability to regain his consciousness was due to many factors, including destiny, emotion, Breathing Style, and bloodline.

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

Sarutobi Hiruzen shook his head.

"We cannot touch the bloodline of demons for the time being."

"After all, even if it could recover,"

"There is no guarantee that accidents won't happen during that long, drawn-out period of mental instability."

Sarutobi Hiruzen did not want to entrust his life to anyone else.

"And even if it does recover..."

"Whether the newly shaped species retains the original personality,"

"Or develops an entirely new soul,"

"Is impossible to say for sure."

Sarutobi Hiruzen examined the first Perfect Being in the world before him.

He decided to name it Perfect 1.

"However, even so..."

"This experimental subject holds immense significance."

"After all, the difficulty of going from zero to one is completely different from going from one to a hundred."

"With this zero-to-one process of the Perfect Being achieved..."

"It is only a matter of time before we develop a technique to graft the Perfect Being's bloodline without side effects."

"It's just that by then, I might have found an even more perfect way to solve the problem of lifespan."

Sarutobi Hiruzen resealed Perfect 1 using his methods.

"Furthermore, compared to ninja techniques,"

"Even a corpse can be used to kill, let alone such a perfect Biological Weapon."

With an immortal body, limbs that could change into anything, physical capabilities far exceeding ordinary people, the potential for evolution, and a highly stable genetic structure.

In Sarutobi Hiruzen's eyes, it was simply the perfect Biological Weapon.

It was far superior to something like the T-Virus.

At the ancestral estate of the Ubuyashiki Clan, The Ubuyashiki Clan Head was discussing matters regarding the Demon Slayer Corps with Tsukiguni Yoriichi.

Sarutobi Hiruzen arrived unannounced at that moment.

"Lord Sarutobi..."

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

"It is wonderful that you have come."

"Now that the members of the Demon Slayer Corps have basically learned Breathing Styles,"

"We finally have the capital to fight against demons."

"There are already swordsmen capable of slaying demons on their own..."

"So Yoriichi and I were discussing the matter of purging the demons in the Kyoto region."

"It would be best if you could participate as well."

Hearing this, Sarutobi Hiruzen said, "A full purge would be difficult, as the Demon Slayer Corps has only just learned Breathing Styles and their combat power is still limited..."

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

"As for the vast number of man-eating demons..."

"As long as we kill the Demon King Muzan, those demons will perish on their own."