Uchiha Ignites the King Engine

"Shadow Clone, dispel!"

Poof!

The two shadow clones stationed within the Underground Laboratory dissipated into puffs of white smoke upon the command.

Toji slowly withdrew his gaze and began to tally the day's gains.

As expected of himself.

Even as shadow clones, their progress in research was in no way inferior to his original body, having already achieved a breakthrough at this stage.

"Yin Seal."

He whispered, forming hand seals.

The next moment, a diamond-shaped black mark appeared at the xiphoid process, resembling the timer of an Ultraman. The core for storing chakra had been successfully constructed and was currently slowly absorbing the physical energy that leaked from his body daily.

With only the storage of mental energy and the synthesis of the two into chakra remaining, he would be able to officially activate his chakra reserves.

He was one major step closer to truly rewriting the Yin Seal and making it his own.

This breakthrough was not some useless facade like the previous attempts, but one that possessed genuine, practical energy-storage capabilities.

What did storing physical energy mean?

It meant that while Toji was awake during the day, he could continuously collect the physical energy leaking from his body. When he felt exhausted at night, he could release this accumulated energy at will to replenish his vigor.

It effectively removed "sleep," a human instinct, from his daily routine.

Have you ever seen Konoha at four in the morning?

Toji was about to see it.

The enhancement of his stamina would also increase his available time each day once more.

With his original body and shadow clones, while others only had 24 hours in a day, he had 48 or even 72.

He couldn't finish living it; he simply couldn't finish living it.

Of course, maintaining this near-perpetual motion state came with a price.

The Yin Seal and the research into Reanimation were both frantically draining his energy. The exponentially compounding fatigue surged back like a tide, leaving his mind exhausted.

Toji could clearly sense that the weakest heart within his body was on the verge of necrosis under such continuous, high-intensity strain.

The heart of an ordinary genin had become a consumable item in his hands.

It would never last until the day of natural aging.

It was no wonder ordinary ninjas dared not use the Yin Seal; without some special constitution, using shadow clones would truly kill you.

If shadow clones were this taxing, the advanced Multi Shadow Clone technique was likely something only someone with the multi-layered buffs of Naruto Uzumaki could use as they pleased in the Ninja World.

However, Toji had anticipated this long ago.

Necrosis?

He would just replace it.

After personally cleaning up the traces in the Underground Laboratory, Toji returned to the surface and lay back down on his bed.

He no longer needed to worry about physical energy, as the Yin Seal had already begun to take effect, but the deficit in mental energy was real. He still required sleep to replenish that portion of the loss.

Moreover, unless necessary, due to the human instincts and emotions rooted in his bones, Toji had no intention of completely abandoning "sleep," a process that allowed his body and mind to briefly empty themselves.

Tomorrow, he had to deceive Uchiha Chirori...

He needed to replenish his energy all the more.

Toji closed his eyes.

The following evening.

The setting sun dyed the stone slabs of the Uchiha Ninjutsu Training Ground a warm orange, and the evening breeze carried the faint scent of scorched earth from Fire Style techniques.

In the corridor.

Uchiha Chirori rested her cheek on one hand, her elbow propped on her knee, her purple hair swaying slightly in the breeze.

She tilted her head to look at Toji, who was sitting beside her. "Today's Fire Style training is already over. Toji-kun, is there something special you need to see me about?"

Based on their usual dynamic, Toji never took the initiative to find her outside of ninjutsu training or weekends, let alone with such an unusual expression on his face.

Toji remained silent for a moment; an expression rarely seen on his face—something that could be called "hesitation"—appeared.

He spoke slowly, "Yes... there is something I need to tell you."

"I have a technique I intend to teach you, Chirori."

"A technique?"

The curiosity in Uchiha Chirori's eyes deepened. "What kind of technique is it? Could it be... Medical Ninjutsu?"

In her impression, all of Toji's ninjutsu and research were related to medicine.

"It is not Medical Ninjutsu; it is a Sealing Technique." Toji said, solemnly pulling an ancient-looking scroll from his robes and handing it to Chirori. "It is called the Yin Seal."

Yin Seal!!

Uchiha Chirori's pupils constricted.

As a legendary ninja who had followed Uchiha Madara and Uchiha Izuna through the wars of the chaotic era, she naturally knew of the Yin Seal; it was a technique she had experienced firsthand.

It was the signature ninjutsu of Uzumaki Mito, the wife of her former nemesis Senju Hashirama, and a closely guarded secret of the Uzumaki clan.

She did not know the specific principles or the full extent of its utility.

But she would never forget it.

Once, during battle, Uzumaki Mito had released the Yin Seal, and a volume of chakra so vast it was nearly terrifying had poured forth. High-level ninjutsu were unleashed one after another as if chakra were infinite, and the saturation bombardment had suppressed her—back when she only possessed the Three-Tomoe Sharingan—leaving her in a state of utter humiliation.

Therefore...

Her impression of the Yin Seal was profound.

"Toji, where did you obtain this technique?"

Chirori spoke instinctively, but the moment the words left her lips, she felt her question was laughable.

Anxiety clouds judgment; she had even forgotten such basic common sense.

A secret technique like the Yin Seal—who else could have given it to him but Lady Mito? It couldn't possibly have been stolen or seized. Even Uchiha Madara could never accomplish such a feat within the Senju Compound.

He would be beaten by the husband-and-wife duo.

"Did Lady Mito give this to you?"

She reached out with both hands, her expression solemn, and took the scroll from his grasp.

"Mm." Toji nodded slightly. "To be precise, it was a gift decided upon by both the Hokage and Lady Mito."

"Then you..."

"You must have many questions. Before I answer them, look at the contents of the scroll first."

"Alright."

Uchiha Chirori slowly unfurled the scroll across her knees.

The scroll was quite long, and to keep the end from trailing on the floor, she naturally laid the other side across Toji's lap, lowering her head to study it intently.

The further she read, the more astonished her expression became.

[Yin Seal: Used to accumulate and store chakra; it can also preserve one's appearance and maintain a youthful visage.]

She noticed the preservation of youth first, only then registering the function of storing chakra.

No woman could resist the temptation of retaining her beauty and delaying the aging process.

Moreover, Chirori suddenly recalled Toji mentioning the Zenin clan's innate longevity to her.

Thump, thump—

The air was so quiet it felt stagnant; she could even hear her own heart beating violently. The last time she had felt such a surge of emotion was the moment she awakened her Mangekyou Sharingan.

She realized something, and at the same time, she noticed that in order to read the scroll, she and Toji were sitting far too close.

Her throat felt slightly dry as she spoke softly, "Toji, you..."

"Shh."

Toji pressed a finger to his lips, his voice gentle and soft. "Everything you are thinking right now is correct, but please don't say it out loud yet. The Yin Seal is very difficult to master, and I don't want to put too much pressure on you."

He paused, his deep, magnetic voice ringing slowly against her ear:

"Beyond what you are thinking, I need you to learn it. Afterward, I will conduct some experiments on you to help you completely cure your Bloodline Disease."

Chirori could no longer hear the words that followed.

The phrase—your thoughts are correct—echoed repeatedly in her mind.