Eternal Mangekyo

"Ah, so you recognized me." The young man smiled and raised a finger to his lips. "Keep it quiet. If you scare Hidden Leaf Village into paralysis, I won't get to have my morning tea."

"Well, well... what an unexpected windfall..."

Kakuzu looked utterly thrilled, the light in his eyes trembling nonstop. "580 Million Ryo... that's what your head is worth! The Five Great Nations jointly funded it, and every Exchange Station in the shinobi world has pledged to honor it!"

"Good. That's exactly the reaction I was hoping for. But..." The young man curled his lip in mild dissatisfaction. "My head is only worth this much? Looks like even if I carried my own head to Bochi, I still wouldn't be able to trade it for the sage arts in his possession."

This young man was none other than Uchiha Shin'yu.

Back then, after Uchiha Kagami turned into a tree, he returned to the base and transplanted his younger brother's Mangekyo Sharingan under Uchiha Madara's guidance.

The process had been rather complicated. The path to eternity was far from simple.

It was known that after awakening the Mangekyo Sharingan, every use of Eye Power or ocular techniques generated a special kind of Yin Release Chakra within the mind. This strange energy could make its wielder stronger and greatly increase their Mental Energy. However, as Yin Release Chakra accumulated, it also damaged the optic nerves and gradually eroded every cell in the body, causing the wielder to grow weaker by the day.

Over time, the result was clear: Mental Energy steadily increased while physical energy gradually weakened. This was the so-called excess yin and deficient yang.

Once enough Yin Release energy had accumulated in the mind, transplanting the Mangekyo Sharingan of a blood-related relative would allow that energy to slowly merge with the new eyes. Bloodlines fused, genes reshaped, and the innately incomplete sequence was restored to completion. After sufficient time, a complete transformation would follow.

That was the path to eternity.

Once successful, not only would the eyes undergo complete evolution and see their basic attributes and ocular techniques greatly enhanced—unlocking full forms of Susanoo, for example—but they would also fuse all the Eye Power from the other pair of eyes, becoming an Eternal Mangekyo Sharingan that would never go blind.

According to Madara's experience, successful fusion required one crucial condition: the optimal moment for transplantation.

It was the instant when the original eyes went completely blind—the same instant when the Yin Release energy in the mind reached its peak.

In the past, Shin'yu had always erased the Mangekyo Sharingan's negative effects by turning back time, restoring himself to an unharmed state. But doing so also erased the newly generated Yin Release energy in his mind.

Therefore, Shin'yu had to relentlessly drain his Eye Power until both eyes had gone completely blind before he could transplant Kagami's Sharingan.

For an entire month, he constantly restrained the urge to turn back time. It was no different from suppressing an instinct. At the same time, he used ocular techniques without regard for the cost, squandering his Eye Power like a nouveau riche. He even used Susanoo to pour himself tea.

At last, after nearly insane expenditure of Eye Power, he went blind.

Yet unlike what he had expected, his body did not weaken much, nor did he develop the so-called coughing-blood symptoms.

Still, everything remained within controllable limits. He decisively removed Kagami's Mangekyo Sharingan from the nutrient solution and completed the transplant surgery.

Everything proceeded according to plan.

In just three short months, he completed the fusion and opened those eternal eyes.

Those eyes shone crimson like Vermilion Jade. A Trefoil of Ink-colored patterns had appeared amid the original Magic Array markings. They were exquisite and magnificent, dazzling like Glazed Tile, with faint purple light glimmering amid the scarlet.

Even Uchiha Hikari, standing nearby, covered her little mouth and cried, "Beautiful."

By the usual process for Mangekyo fusion, this meant success.

But Uchiha Kagami's eyes were no ordinary Mangekyo.

They were a pair of eyes that had perfectly fused with Hashirama's genes and inherited pure Yang Release Chakra.

Though he had completed the Yin Release fusion, the Yang Release fusion remained an unknown and lengthy process.

Every day, Shin'yu experienced something new: his physical body, already at the pinnacle of perfection, was still slowly growing stronger day by day!

The eyes of a blood relative had opened a path for bloodline fusion. Through that path, the Yang Release genes originally contained within those eyes were also merging with every cell in Shin'yu's body. This was reconstruction at the genetic level, and the sequence ratios were nothing short of perfect!

The process was painless, but if Shin'yu used his Eye Power, the fusion would fall into prolonged stagnation and would not slowly resume until months later.

For that reason, to avoid unconsciously consuming Eye Power, he simply covered his eyes and allowed the yin and yang powers to fuse naturally without any interference, gradually completing the process of strengthening his body.

Given enough time, he would gain the Yang Release power Kagami had once displayed—and it would come without any side effects, without backlash, entirely belonging to Uchiha Shin'yu.

Black Satin wrapped around his eyes, and he wore it for six years.

During that time, as long as he did not deliberately interfere, Shin'yu's body would continue to evolve at a slow pace. He grew stronger bit by bit even while eating and drinking. This subtle evolution penetrated every cell, extracting ever-denser Yang Release Chakra.

This was not someone else's Yang Release Chakra, but Yang Release Chakra actively produced by his body after genetic alteration.

The progress was slow, but the accumulated results were terrifying.

Shin'yu vaguely felt that he was about to break through the bottleneck.

"Tap, tap, tap..."

Across the table, Kakuzu set down his cup, his hand trembling incessantly from excitement.

"Don't be in such a hurry to make a move. If we're going to fight, let's go outside. I rather like this place," Shin'yu said softly.

"Fine." Kakuzu narrowed his eyes, a miserable green gleam leaking through the slits. "A prey that knows it is about to die yet remains so calm... you're the first."

Shin'yu found it rather amusing. "Kakuzu, aren't you curious why the Five Great Nations jointly put a bounty on me—and why it's so high?"

"Does a lion care whether the sheep it eats today is the lead ram?" Kakuzu asked indifferently.

"Or it could be Satan..." Shin'yu muttered softly.

"What?"

"Nothing."

"Hmph. I only care about the bounty. Nothing else matters." Kakuzu's words brimmed with confidence. "I already possess an immortal body. Even a Kage can be killed at my leisure!"

A "heh heh heh" laugh emerged from beneath his mask.

So the Five Great Shinobi Villages had tacitly kept the information about my battle with Hashirama hidden...

Shin'yu asked, "So I can take it that you've abandoned your original target and decided to hunt me instead?"

"Hm?" Kakuzu immediately became suspicious. "How did you know I had another target?"

He had indeed come to Hidden Leaf Village for another target: Hidden Leaf Village's current Third Hokage, Sarutobi Hiruzen.

Back then, the First Shinobi World War had inflicted enormous losses upon every major nation. Four leaders—the Second Hokage, Second Raikage, Second Water Shadow, and Second Earth Shadow—had all perished one after another during the First Shinobi World War, along with countless elite shinobi who were buried on the battlefield.

Since every major nation had suffered massive losses in combat strength and lost its foremost leader, the First Shinobi World War gradually subsided. After the war, the nations tacitly entered into a truce agreement, and the world entered a period of peaceful development.

And this Sarutobi Hiruzen had taken office three years ago. After passing through layers of voting, he had been personally appointed by the Feudal Lord as Hidden Leaf Village's Third Hokage.

"Of course." Shin'yu chuckled and lowered his voice. "Because I was the one who issued that bounty."

"What?!" Kakuzu froze slightly, his gaze instantly turning alert. "No wonder. Someone offered 90 million ryo for the head of a newly appointed Hokage! You have a grudge against him?"

Shin'yu could not hold back his laughter.

"Kakuzu, I like how straightforward you are. My target is you!"