A few more months passed. The snow of the Warring States Period melted completely, and fresh green growth spread across the branches as all things came back to life.
In the dilapidated laboratory hidden beneath the Dragon Vein, Yue Uchiha was making his final deductions, studying the notes on the "Spring of Returning Light" left behind by Grandma Chiri.
The floor was covered in dense calculations and diagrams of chakra flow, with a few drained white mice scattered nearby.
The so-called "Spring of Returning Light" was, in essence, neither a mysterious curse nor a sacrifice.
It was simply an extremely crude and forceful "high-pressure pump."
Put simply, the Tomoe Sharingan was like a container holding water, and ocular power was the water.
When Uchiha clan members fought using the Tomoe Sharingan, the water flowed out to attack their enemies.
While they rested, their bodies slowly produced new water through their souls to replenish it.
But the Mangekyo Sharingan was different.
There was a big hole in the bottom of its container, and the water was too pure—the quality of ocular power it required was too high for the soul to replenish.
Once awakened, no matter how much you rested, water would keep leaking through that hole, impossible to replace, until the container ran dry. That was blindness.
The Spring of Returning Light worked by forcibly crushing other clan members' containers, then pouring all the water inside—even the shards of the containers—through pipes, or rather, a formation, and into the Mangekyo.
But because the water was impure and there were too many shards, the Mangekyo's user inevitably suffered mental damage.
As for how well it worked?
Although the water was impure, there was plenty of it—just enough to let the Mangekyo Sharingan be used.
However, the power of its ocular techniques was ultimately weaker than that of a Mangekyo's natural abilities. For instance, it couldn't use the complete Susanoo, and in a clash with a true Mangekyo Sharingan, the user would be at a disadvantage in terms of mental strength.
Still, being able to use it at all was the best news.
The principle behind it was actually quite simple.
And based on that principle, Yue had made improvements.
Over the past few months of research, Yue had drawn on his theoretical memories of Tsunade's Strength of a Hundred Technique and Yin Seal from a later era. At last, he had found a relatively perfect alternative.
Put simply, it was like building a reservoir—or a battery.
Tsunade's Yin Seal stored excess chakra in her forehead bit by bit, accumulating it over time so it could be released in a burst at a critical moment.
Yue's improved "simplified Spring of Returning Light formula" worked on the same principle.
It gathered naturally replenished ocular power—the "water" produced by the Tomoe Sharingan through rest—and stored it. Then, when the Mangekyo was activated, that reserve could be used to replenish it.
The water might not be as pure as the "pure water" the Mangekyo came with, but its effects were about the same as the ocular power replenished by the Spring of Returning Light. No, they were probably better, since this ocular power came from his own soul.
In other words, Tsunade's Yin Seal stored chakra, while Yue's seal stored ocular power.
"Just as I thought, I'm a genius." Yue smiled confidently.
In his future plans, this battery could theoretically be arranged in parallel or in series—in other words, multiple people could act as batteries and supply power to a single person.
So he had optimized the structure on that basis, leaving room for modules that could be added later.
It was his last little attachment to his past life as an architect.
The concept still needed to be tested in Rōran. For now, he just wanted to leave this era as quickly as possible.
Then he walked over to Hikari, gently cupped her little face, and looked into her clear black-and-white eyes.
"Keep your eyes on me. I'm going to use my own body for an experiment. If it works, our Mangekyo Sharingan will never run out of ocular power again."
At Yue's words, a rare hint of nervousness flickered in Uchiha Hikari's usually vacant eyes.
She obediently took half a step back, but her hands clenched the hem of her clothes without thinking. She stared fixedly at Yue.
Yue took a deep breath, picked up the special brush beside him, and dipped it into ink mixed with his blood and special medicinal herbs. He began drawing intricate Sealing Jutsu across his forehead, around his eyes, and down his cheeks.
The black symbols flowed like slender snakes before converging at the center of his brow.
"I'm calling this formula the 'Ming Seal.'"
Yue sat cross-legged and formed an extremely unusual Hand Seal.
"Seal!"
At Yue's low shout, the black symbols on his face glowed with a faint blue chakra light. Like countless rivers flowing into the sea, they rapidly contracted toward the center of his brow and gathered there.
"Ugh!"
Yue let out a muffled groan.
Forcibly altering the flow of his mental energy and ocular power brought a tearing pain deep inside his brain.
But the pain lasted only a few seconds before receding like a tide.
Once all the black symbols had disappeared into his brow, a tiny, faint, dark-purple diamond-shaped mark remained.
The mark was now fully automated, able to store the "water"—the ocular power he produced while resting.
Judging by the results, it had worked.
But Yue didn't stop. He abruptly opened his right eye, and his Mangekyo began to spin as its ocular power drained rapidly. The dark-purple diamond-shaped mark began to glow.
When the time was right, Yue quickly formed a Hand Seal.
"Release!"
The reservoir he had just built opened its floodgates!
A surge of pure ocular power, belonging entirely to him, rushed through specific pathways and poured into his left eye, which had long been completely blind and dull.
Under Hikari's astonished gaze, the gray haze of death in Yue's left eye was swept away in an instant.
A crimson hue spread over the white of his eye. Three black Tomoe slowly appeared, then spun together like meshing gears, forming the deep, mysterious pattern of the Star Dice!
The Mangekyo Sharingan in his left eye had regained its light!
Meanwhile, his right eye quickly dimmed. Its ocular power had not returned to normal, and it looked as if it might go dark at any moment.
Clutching his newly restored left eye, Yue couldn't help but burst into laughter.
Though both his eyes were still in terrible shape, with this formula they had completely escaped the curse of blindness. It was like having the beginnings of a sustainable "Eternal Mangekyo"!
"Yue... your eye is shining again."
Hikari stared blankly at the eye glowing crimson once more. Her tightly clenched hand finally relaxed, and she let out a long breath.
"Come on, little girl. Your turn."
In high spirits, Yue pulled Hikari in front of him, washed the brush in warm water, and dipped it into the special ink again.
"Once I fix your eyes too, we can go home."
Hikari let Yue draw across her fair little face.
When the cool tip of the brush touched the corner of her eye, she asked softly, "Home... where is that? There's no place for us among the Uchiha anymore."
"Who said we're going back to the Uchiha?"
Yue expertly finished the final stroke of the seal, then placed both hands against Hikari's temples and guided her chakra toward the center of her brow. "The place we're going has no Elders and no endless killing. It has a towering steel city, all the grilled fish you can eat, and... absolute freedom."
As the seal took shape, a small diamond-shaped mark appeared on Hikari's brow as well.
"Just get plenty of rest, and it'll store ocular power. When you want to use your Mangekyo, just copy my hand sign and release the seal."
Hikari blinked her adorable eyes.
"All right. Pack up. We'll rest for the night and go home tomorrow."
Yue stood and stretched his limbs. The last of his attachment to the Warring States Period had vanished with Chiri's passing.
Tomorrow, it would be time to leave.
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