[Scroll of Sealing]

A secret chamber deep inside the Hokage's office in Konoha.

The air was stifling and oppressive. The only light came from the flickering candles on the walls, which illuminated the enormous scroll on the stone platform in the center.

Hiruzen Sarutobi personally brought Orochimaru here and solemnly undid the seal on the scroll.

"Orochimaru, remember: every jutsu in here could have disastrous consequences."

"Research is fine, but you must never misuse them."

"Furthermore, this scroll must not be taken from this room."

The Third's voice was imbued with unquestionable authority.

"Yes, sensei."

Orochimaru bowed slightly, though his eyes had already been drawn to the ancient scroll spread open before him.

After Hiruzen Sarutobi left, the stone door to the secret chamber slowly closed, cutting off everything outside.

Only then did Orochimaru straighten and walk over to the stone platform, his gaze falling on the scroll.

This was Konoha's secret treasure, the Scroll of Sealing, which recorded countless forbidden jutsu...

He took a deep breath, suppressed his excitement, and began to examine it carefully.

The first jutsu to catch his eye was the Multi Shadow Clone Technique.

"Hmm... Its principles are much the same as the Shadow Clone Technique, except that a single set of Hand Seals can create hundreds or even thousands of clones."

Orochimaru skimmed a few lines and quickly lost interest.

A jutsu that relied on an enormous reserve of Chakra to produce a large number of clones lacked technical sophistication and held little value for him.

He continued reading.

The Flying Thunder God Technique.

The pinnacle of Space-Time Ninjutsu, this forbidden jutsu had been invented by the Second and brought to even greater heights by the Fourth Hokage.

It used markers to achieve Instant Transmission, making it quite impressive.

But Orochimaru merely skimmed past it.

The Flying Thunder God Technique was certainly worth studying, but it wasn't what interested him most.

Mutually Multiplying Explosive Tags.

A forbidden jutsu that summoned large numbers of Explosive Tags and set off an endless chain of explosions.

Its power was astonishing, but at its core, it was still just an application of Explosive Tags. It wasn't revolutionary.

Orochimaru's gaze moved quickly over one powerful and bizarre forbidden jutsu after another.

His expression remained calm until...

Impure World Reincarnation!

Those four characters made him stop.

He carefully read the description of the jutsu.

The instructions were quite clear:

First, a living person was needed as a vessel for the soul's arrival.

Second, a certain amount of bodily tissue belonging to the deceased to be summoned was required—for example, blood or hair—to serve as a "coordinate" linking to the dead person's soul.

Third, perform the Hand Seals and cast the jutsu, forcibly summoning the deceased's Chakra (soul) from the Pure Land to the World of the Living and binding it to the vessel.

The jutsu was complete.

The pages even included detailed instructions for the Hand Seals, along with precautions for the ritual.

"So that's all there is to it..."

Orochimaru studied the notes, sinking into deep thought.

In principle, the jutsu wasn't particularly complicated.

Its core could be broken down into two parts:

The first was the "search" mechanism.

Using the deceased's living tissue as a unique "keyword," it precisely located the target's Chakra information in the database of the world of the dead known as the Pure Land.

The second was "summoning and possession."

A specific jutsu forcibly pulled the located Chakra (soul) from the Pure Land back into the real world and attached it to a prepared vessel, completing the "reincarnation."

"Interesting...

"Unfortunately, this jutsu is probably still only a prototype."

Orochimaru murmured, shaking his head with some regret.

He had already wondered about this. Given the Second Tobirama Senju's character and pragmatism, if Impure World Reincarnation had truly been perfected to the point where it could summon powerful people at will, how could he have not used it during the First Shinobi World War?

If he had summoned the First Hashirama Senju and Madara Uchiha, the entire Ninja World would have been crushed beneath Konoha's heel.

It seemed the jutsu was still only a prototype...

Orochimaru's eyes glimmered with thought.

In any case, he considered it far more valuable to study than anything he had seen so far.

"This will be my next research project."

Orochimaru nodded. The Impure World Reincarnation jutsu might touch upon the true nature of Chakra as a form of energy.

Ordinary Five Elements jutsu, whether Fire Style, Water Style, or Lightning Style, essentially used changes in the properties of one's Chakra to imitate the "characteristics" of natural phenomena such as flames, water, and lightning.

For example, the Fire Style: Fireball Jutsu didn't produce flames made of plasma in the true sense of the word. Instead, it released a mass of Chakra energy endowed with the properties of fire, such as high temperature and combustion.

At its core, it was still Chakra.

That was also why the Karma of the Ōtsutsuki Clan and certain special Sealing Jutsu could absorb these jutsu.

Because they absorbed the Chakra that made up the jutsu itself.

In theory, performing these Five Elements jutsu required only two steps:

First, change the Chakra's properties, giving it a specific attribute.

Second, change its form, shaping the Chakra with that attribute into the desired form, such as a fireball, a water dragon, or a spear.

His teacher, the Third Hiruzen Sarutobi, was renowned as the "Professor of Ninjutsu" because he had mastered changes in Chakra's properties and form to an extraordinary degree.

For the Third, there wasn't much difference between using Fire Dragon Bullet and Water Dragon Bullet, or Fireball and Wind Cutter Technique. They were all just different combinations of attributes and forms manipulated through Chakra.

Yet this still remained on the level of "using" Chakra as a form of energy.

It was like how humans had learned to use fire to keep warm, provide light, roast food, and even forge metal, but that didn't mean they understood the chemical nature of "combustion."

Ninjutsu itself was a technological black box. Users didn't need to understand how it worked; they only needed to use Hand Seals to guide Chakra along specific pathways in the body and activate the corresponding jutsu.

Put simply, it was much like a handgun. You didn't need to understand how one worked; you just had to pull the trigger.

These jutsu never truly delved into the core question of what Chakra actually was.

But Impure World Reincarnation...

It directly connected with the so-called Pure Land and summoned the dead's Chakra (soul).

And the summoned dead could use all their abilities at full strength, even activating their Kekkei Genkai.

This could no longer be explained by simple changes in Chakra's properties and form.

It might already have touched upon the mysterious realms between Chakra and the soul, life and death.

That was the fundamental knowledge Orochimaru truly longed to explore!

But...

Orochimaru's brow furrowed slightly.

The Scroll of Sealing only recorded the "instructions" for using Impure World Reincarnation.

As for how the Second had developed the jutsu...

What was its theoretical basis? What attempts and failures had occurred along the way?

The related research notes and experimental data...

There was nothing!

"Only instructions for using it, but no development process or detailed explanation of its principles..."

He was somewhat disappointed.

Without theoretical foundations or research records, it would be extremely difficult to reverse-engineer the complete principles from a mere set of instructions.

"Where would the Second's research records be kept?"

Orochimaru's gaze flickered.

Tobirama Senju.

The name immediately brought someone else to mind.

The Senju Clan's... Tsunade!

Perhaps the Senju Clan's estate still held the Second's research materials on Impure World Reincarnation.