February 19th, around noon.
Hyuga Yu and Kakuzu arrived at Numazu, the capital of the Land of Rivers.
As a buffer zone between the Land of Fire and the Land of Wind, the Land of Rivers served a strategic function in balancing the power of the two great shinobi nations. Much of its territory consisted of undeveloped natural landscapes, where dense vegetation and complex terrain provided excellent natural cover.
To put it bluntly, it was a total backwater.
Though designated as the capital, it was actually just a small city utilizing a highly traditional Japanese castle-within-a-castle layout. The already modest city was divided into an inner and outer section. The outer town presented a dilapidated, swampy sight, surrounding a relatively short district of low, sprawling wooden buildings. From the city gates, one could easily look straight into the center of the inner town to see the towering tenshu where the nobility of the Land of Rivers resided.
After entering the city, Yu found a mediocre but reasonably clean inn to stay at.
Of course, during the interval spent waiting for Kakuzu's intelligence to arrive before they set out to hunt Hiruko, he didn't idle around.
Yu continued his research into his newly acquired jutsu.
And the subject of his research happened to be Kakuzu.
At this moment, inside the spartan inn room, Kakuzu wore an expression of complete resignation. He placed one hand on the table and, at Yu's request, undid the stitches on his palm. Bundles of black Earth Grudge Fear threads sprouted from the opening, presenting themselves to Yu, who was currently pulling an assortment of bottles, jars, a microscope, and experimental equipment from a storage scroll.
Sprouting Earth Grudge Fear threads was a simple task for Kakuzu. He could alter their length and shape at will, allowing him to handle any situation...
However, on some level, those threads were practically a part of Kakuzu's own body. Now... watching a part of himself being treated as experimental material—constantly sliced up, dipped into strangely colored solutions, observed under a microscope, with the findings recorded in a notebook—Kakuzu's mood became incredibly bizarre. He felt a strange sensation, akin to a starving man during a famine who had no choice but to chop off his own hand and deep-fry it.
He turned his head, his glowing green eyes fixated on Yu, who was so immersed in his scientific world that he seemed entirely oblivious to how bizarre his actions were. Kakuzu asked in a muffled voice, "What exactly are you doing?"
"The part of Earth Grudge Fear on your own palm is already under your control. By all accounts, you should already be able to do exactly what I do. Why do you still need to use... mine?"
Without even looking up, Yu quickly jotted down a set of matching data regarding the connection between Earth Grudge Fear blood vessels and the tail vessels of a lab mouse in a notebook he had obtained from Konan. Taking a brief moment to respond, he said, "It's a control experiment."
"From the perspective of Yang Release, Earth Grudge Fear is essentially a highly controllable extracellular matrix and vascular tissue engineering system. Theoretically, it can modify the circulatory system at will, which is the root cause of an 'immortal body' like yours."
Kakuzu didn't understand the jargon, but he was curious. "What does that mean?"
Yu set down his notebook, glanced at him, and patiently explained, "To put it simply, with this ability, you can use other people's body organs and tissues to replace your own at will."
"Mr. Kakuzu, your current body shouldn't be your original one, right?"
Hearing this, Kakuzu froze slightly. He had never really given the matter much thought. After pondering for a moment, he replied, "When injured, I have indeed taken the bodies of my enemies to sew myself back together."
"Is that supposed to be strange?"
Yu stared at the data in his notebook, a flash of excitement gleaming in his eyes as he chuckled. "No, it's not strange. To you, it's an everyday occurrence. But if these findings were introduced to the medical community, they would trigger a magnitude-10 earthquake across the entire field!"
"That exaggerated?"
Yu nodded. "Because it means Earth Grudge Fear can match with any cell, blood type, tissue, or organ without causing any transplant rejection. In medicine, we call such a thing..."
"A panacea."
Kakuzu remained somewhat puzzled. Looking at Yu, he asked, "Then what use is this to you?"
Yu pondered for a moment, estimating, "My primary research topic right now is exploring a method to perfectly fuse genetic lineages to achieve my goal."
"Hiruko's Chimera Technique is crucial. Theoretically speaking, it should be a form of genetic chimerism technology capable of breaking species boundaries to fuse the cells and genes of different organisms."
"But looking at the manifestation of this jutsu, there is an unavoidable problem that simply cannot be bypassed..."
"Rejection."
"Even when the Uchiha clan was still around, Hiruko didn't choose to capture a pure Uchiha. Instead, he targeted Kakashi Hatake, an ordinary person who had received a transplanted Sharingan. It's highly likely that this was the reason."
"Fusing multiple Kekkei Genkai and lineages carries severe rejection risks. Even someone like Hiruko can only complete the Chimera Technique's fusion by carefully selecting shinobi of equivalent bloodline potency."
"But if this severe rejection can be resolved, then the Chimera Technique will possess infinite possibilities!"
Kakuzu only half-understood, asking, "Are you saying Earth Grudge Fear can solve this problem?"
Yu shook his head. "It can only solve a part of it."
"From the standpoint of synthetic biology, the Chimera Technique is responsible for the gene editing and stem cell technology aspect, whereas Earth Grudge Fear only addresses vascularization and tissue engineering. In other words, even if Earth Grudge Fear is integrated into this system, it only guarantees the forced fusion of different bodily organs under multiple Kekkei Genkai."
"In terms of its manifestation, it's equivalent to combining five people into one."
"The root genetic rejection has not been solved, and the continuity of the nervous system as well as telomere depletion cannot be properly addressed either."
Yu pinched his chin in thought. "To solve the first problem, I need a massive algorithm and processing system capable of integrating target gene fragments from a vast genetic library into a baseline genome, designing an orderly gene circuit that expresses without interfering with each other."
"Solving the second problem requires establishing a perfect biological energy storage system and device to counter the wear and tear caused by cellular overexpression."
"Solving the third problem requires methods involving the soul and consciousness to achieve absolute control over the new body."
Kakuzu could follow along slightly at first, but as Yu laid out the theoretical framework, though Kakuzu recognized every individual word, when put together, he couldn't grasp a single sentence.
Thus, Kakuzu frowned deeply, as if trying to banish the chaotic jargon buzzing in his brain, and asked directly, "So, who else do you need to kidnap?"
Yu already had the answer prepared. Without hesitation, he replied, "Aside from Hiruko's Chimera Technique, Sasori of the Red Sand's Core of Living Flesh technology, and Orochimaru's Living Corpse Reincarnation... theoretically, all of them can be applied to this grand model."
"However," Yu shook his head, "Sunagakure's Sasori of the Red Sand is even harder to track down than Hiruko. Relying on the same methods used to find Hiruko to locate Sasori is virtually impossible. Besides, I don't know much about the materials needed for mechanical engineering."
"The matter regarding the core... we'll worry about it later."
At this point, Yu first looked down at a set of data in his notebook, then lifted his head to look back at Kakuzu, asking with a slight hint of embarrassment, "Mr. Kakuzu, would you mind lending me your Fire Release heart for a moment?"
Hearing this, Kakuzu instantly became guarded. He retracted his palm, shifting his posture almost imperceptibly to slide his chair back a couple of inches. "What are you planning to do?"
"Just verifying an idea."
Yu watched the lab mouse, which now sported a black tail, running anxiously around its cage. He then glanced down at the cyan flame tattoo formed by Earth Grudge Fear on the back of his own hand, his eyes narrowing slightly. "Based on the inherent characteristics of Earth Grudge Fear, I suddenly discovered an intriguing function."
Kakuzu fell silent for a moment, staring intently at Yu for a long while. Finally, he grunted, "You have to find me an excellent Fire Release heart as a replacement, and..."
"This... will cost extra!"
With those words, Kakuzu raised his hands and formed hand signs. An Earth Grudge Fear mask monster wearing a red, canine-faced mask leapt from his back, landing firmly on the open floor of the room.
Kakuzu raised his palm and shattered the mask. Soon after, he reached inside and pulled out a fresh, vividly beating heart.
"Thank you." Yu extended his right hand, took the heart, and gently closed his eyes.
Then, under Kakuzu's intent gaze, the cyan flame patterns on the back of Yu's right hand lit up faintly. Cyan silk-like threads extended from his palm.
The threads wrapped the heart into a cocoon, which then sank inch by inch into Yu's palm. At the same time, individual cyan Earth Grudge Fear blood vessels belonging to Yu wrapped around this living Fire Release heart, moving rapidly through his body—from palm to arm, arm to chest cavity, and finally settling into the right side of his chest.
"Secret Technique: Earth Grudge Fear - Suture!"
Spurring Earth Grudge Fear with Yang Release chakra, Yu swiftly stitched the Fire Release heart into his right chest in a rather rudimentary fashion.
Immediately after, Yu heard a heartbeat echoing from the right side of his chest, completely distinct from the 309-beats-per-second frequency of his own cyan gem-like heart on the left!
Thump! Thump!
Thump! Thump!
Before long, cyan Earth Grudge Fear vessels rapidly connected to the heart, swiftly establishing a new circulatory system within the right side of Yu's body.
As this brand-new organ and circulatory network integrated, Yu gradually felt the Yang Release Tenseigan chakra within him undergo a subtle transformation with every pulse of the heart.
The brilliant cyan hue of the Yang Release chakra began to shift delicately, faintly intertwining with streaks of fiery red. The moment the two colored chakras made contact, a pure golden light, dazzling like the sun, flashed across the interior of Yu's body!
Yu snapped his eyes open!
His pitch-black eyes were instantly dyed a brilliant gold, and a blazing fire resembling molten gold seemed to burn at the center of his deep golden pupils!
A noble, magnificent, and divine aura of majesty suddenly radiated from Yu as those golden eyes shone brightly!
"This is..."
Kakuzu's pupils shrank slightly as he witnessed the inexplicable change occurring in his budget employer. Though he didn't know exactly what had happened, he had a premonition—in that brief split second, Hyuga Yu had somehow grown even stronger!
However, the golden eyes that had manifested within Yu's otherwise ordinary eyes lasted for only a few seconds before showing signs of melting. It was as though his physical eyes could not withstand such a terrifyingly absolute, supreme power!
Or perhaps, they were clearing the way to allow a pair of eyes truly compatible with Yu to grow...
Yu immediately halted the evolution process of the Tenseigan chakra inside his body!
Instantly, his vision blurred.
Having endured the influx of Tenseigan chakra for a mere few seconds, the lenses of his ordinary eyes suffered severe thermal burns, altering their shape and severely degrading his vision.
At the same time, a sudden mass of spiritual energy flooded Yu's mind. After converting this spiritual energy back into chakra, he instantly mastered a B-rank Fire Release jutsu known as Fire Release: Intelligent Hard Work, without any prior training.
"Phew..."
Yu let out a soft breath, rubbing his eyes as they reverted to their normal black color. Once his vision cleared slightly, he slowly raised his hand. In his palm, a ball of intense, high-temperature flame danced to life at his command!
This was undeniably the exact level of Fire Release chakra control that could only be achieved after completing the training for both nature transformation and shape transformation!
Simultaneously, this was the unique effect inherent to Earth Grudge Fear itself—it could assimilate stolen chakra natures, enabling the user to master basic ninjutsu of all five elemental attributes, and achieve a state near immortality by replacing hearts.
By integrating this Fire Release heart, Yu had acquired the Fire attribute, which he previously lacked alongside his Wind, Yin, and Yang attributes.
The moment Yu obtained the Fire attribute and swiftly mastered its control, the Fire factors were spontaneously driven by his Yang Release to fuse with his body and Caged Bird chakra. This unlocked a brand-new, Tenseigan-derived ability rooted in his own Yang Release: [Fire Release: Radiant Sun Fire].
And if Yu could push this jutsu a step further, completing the simultaneous fusion of the Fire, Wind, and Yang attributes, the name of the technique would become—
[Golden Wheel Rebirth Explosion]!
At this moment, Kakuzu stared with profound uncertainty at Yu, who was manipulating the flames dancing between his palms. He simply could not erase the brief scene he had just witnessed from his mind. He immediately questioned Yu, "That just now... what was it?"
"What was what?" Yu raised his head, looking back in confusion.
With a grave expression, Kakuzu scrutinized Yu's eyes, asking uncertainly, "That... golden-eyed form..."
Hearing this, Yu couldn't help but feel a bit amused, realizing that Kakuzu had deeply misunderstood his ability. The golden eyes transformation only looked intimidating; in reality, it was purely a side effect caused by an excessive surge of Yang Release and Fire Release Tenseigan chakra, which had caused his eyeballs to overload and verge on melting.
However, Yu chose not to explain this point. Instead, he adopted a solemn expression and bluffed calmly, "Don't worry about it."
"It's just a little trick I prepared to ensure the success of our upcoming operation to capture Hiruko."
Hearing this, Kakuzu couldn't help but look askance, a subtle... shift occurring in the way he viewed Yu.
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