According to records, the nature transformations of a ninja's chakra are divided into five basic types: Fire, Wind, Lightning, Earth, and Water. In addition, there are two hidden attributes: Yang Release and Yin Release.
When two chakra nature transformations can be fused together and combined with either Yin or Yang attributes, a new type of release technique is formed, known as a Kekkei Genkai (Bloodline Limit).
For example, Wood Release is formed from Water, Earth, and Yang; Ice Release from Wind, Water, and Yang; Storm Release from Lightning, Water, and Yin; and Boil Release from Water, Fire, and Yin.
Since the establishment of the shinobi village system, there has been only one recorded case of a ninja successfully fusing a new Bloodline Limit, and even then, there are no detailed descriptions—only that this individual came from the Hidden Mist Village.
Once successfully created, this new release technique is recorded in the ninja's genes and can be passed down to their offspring through blood inheritance.
Additionally, if a ninja has a physical organ that differs from the norm and grants them unique abilities, it is also classified as a Bloodline Limit. Examples include the Uchiha Clan's Sharingan, the Hyuga Clan's Byakugan, and the Kaguya Clan's Shikotsumyaku (Dead Bone Pulse).
Meanwhile, secret techniques (Hiden) are highly confidential jutsu developed by specific clans or groups through special means and passed down through generations.
In theory, most people can learn secret techniques, as they do not require a special bloodline or innate talent. Instead, they simply integrate Yin and Yang Release into their chakra for practical use.
For example, the Nara Clan of Konoha combines their chakra with Yin Release to develop the Shadow Imitation Technique.
The Akimichi Clan's Multi-Size Technique is created by combining their chakra with Yang Release.
Other secret techniques focus on mastering a single chakra nature transformation to an extreme level, such as the Raikage's Lightning Release-enhanced taijutsu.
Yue closed the book.
These records were different from what he had read before—specifically, the explicit mention of Yin and Yang Release.
However, since Minato had provided these materials, they were undoubtedly credible. This meant that the information Yue had previously accessed through public channels had been censored—likely a protective measure taken by villages and clans to safeguard their Bloodline Limits and secret techniques.
According to this book, there was currently no known method in the shinobi world to directly detect whether a ninja possessed Yin or Yang Release within their body. It could only be determined through bloodline inheritance, long-term training, and observation.
Based on Yue's understanding of Yin and Yang, he believed that Yang Release focused on the body and form, whereas Yin Release emphasized the mind and intent.
For instance, Wood Release and Ice Release could solidify chakra into tangible substances like wood and ice, whereas Storm Release and Boil Release could not form solid structures for attacks.
Yue speculated that the Uzumaki Clan, known for their immense vitality and chakra reserves, likely possessed a natural affinity for Yang Release. However, further investigation was needed to confirm this.
At this point, Yue felt a pressing need to acquire a microscope. Relying solely on these incomplete books wouldn't get him anywhere.
Since he had already decided to stay home and keep Kushina company, his activities were limited to reading, refining chakra, and researching sealing techniques and the Kagura Mind's Eye.
But other matters needed to be addressed as well.
One particular detail stood out to Yue: once a Bloodline Limit was successfully fused, it could be genetically passed down, becoming an inherited bloodline power. This greatly intrigued the gene master in him.
However, obtaining a microscope was problematic. Outside of hospitals and certain research departments, almost no one owned one, given that people in this world lacked scientific knowledge and awareness.
Moreover, a microscope could easily be associated with human experimentation—an issue made all the more sensitive by Orochimaru's infamous past. If Yue were to ask Minato for one, explaining his reasons would be a real headache.
Yue neither wanted nor was good at handling such matters.
Just as he was struggling with this dilemma, a sudden realization hit him.
"Have I let my brain rust these past few years? If I don't have one… why not just make one myself?"
With that thought, Yue immediately drafted a list of necessary materials.
Even though a rudimentary microscope would only allow him to observe cells and not delve deeper into their internal structures, progress had to be made step by step. Nothing could be accomplished in one go.
Once the list was ready, Yue took enough money with him, informed Kushina, and headed out.
After visiting several shops, he finally found lenses that met his requirements. The other materials were relatively easy to gather.
Hurrying back home, he sat at his small desk and spent some time assembling everything. Soon, a simple microscope was completed.
He then pulled the curtains shut, borrowed a flashlight from Minato and Kushina's room to focus light, and turned his attention to the next issue: the sample.
Yue found a glass slide and bit off a piece of flesh from his own finger, placing it on the slide. (Subcutaneous tissue cells are the most intact.)
Since blood cells consisted of multiple types and most were anucleate, he decided to examine subcutaneous tissue cells first.
He carefully placed the slide under the microscope.
To Yue, cells were one of the most mysterious aspects of the universe. He had no idea how the first cell was created—perhaps that question would never have an answer.
But what he could do was observe them up close. The deeper he studied them, the more fascinated he became by these seemingly tiny yet profoundly complex building blocks of life.
Under the microscope, Yue noticed something astonishing—his detached subcutaneous tissue cells displayed an extraordinarily high level of activity! He could even see the cytoplasm frantically moving, exchanging materials at a visible rate!
This was unbelievable!
The microscope's magnification only enlarged the cell nuclei to about the size of a sesame seed, so the cells themselves weren't much bigger.
But even with such a limited view, he could clearly see the intracellular material exchange—something that, based on his prior experience, should have been impossible!
Human cells shouldn't be this active.
This meant that his body's cells were vastly different from those of his previous life. To him, his current body felt like a volcano—brimming with boundless energy.
After observing for a while, Yue lifted his eyes from the microscope, deep in thought…
He realized that he lacked sufficient samples to determine whether all people in the shinobi world exhibited such cellular properties or if this trait was unique to himself or the Uzumaki Clan.
However, acquiring samples would be tricky—he couldn't just sneak up on someone in the street and cut off a piece of their flesh…
And he definitely couldn't experiment on Minato or Kushina. While it wouldn't cause any harm, explaining it would be a nightmare.
After thinking for a while, Yue set his sights on two people—he figured they wouldn't be a problem.
Uchiha Itachi and Kurenai Yuhi.
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