From what Hyuga Kagami remembered, when Toneri Ōtsutsuki transplanted his eyes on the Moon, he went through a fairly long adaptation period before successfully evolving the Tenseigan.
Because of that, Kagami had deliberately delayed activating his own Tenseigan plan.
But the situation had changed.
Although he couldn't tell exactly what the village was planning, one thing was certain—danger was closing in.
Seizing an opportunity during a solo patrol, Hyuga Kagami arrived at a remote spot in the desert that he had chosen long ago.
After carefully surveying the area with his Byakugan and confirming that no one else was nearby, he immediately formed hand seals and summoned the One-Eyed Viper Orochimaru had left behind to keep watch over him.
Poof—
In a puff of smoke, the One-Eyed Viper lazily slithered onto the sand in front of Kagami and spat out a scroll from its mouth.
As expected, the scroll containing the gene fluid had always been stored inside the snake.
This was a necessary precaution. Only by keeping it in the One-Eyed Viper's body could Kagami retrieve the precious gene fluid anytime, anywhere using the Summoning Jutsu.
As for whether Orochimaru might intercept it—there was little need to worry.
Long ago, Kagami had already begun storing all sorts of miscellaneous experimental materials inside the snake. Orochimaru had secretly checked a few times, but after finding nothing of value, he gradually stopped paying attention.
Moreover, Orochimaru had only just defected. At this moment, he was likely entangled with Jiraiya and wouldn't have the time or energy to worry about Kagami anytime soon.
Taking the gene fluid out of the scroll, Hyuga Kagami's expression turned grave.
Genetic-level evolution carried far too many unknowns.
The fluid before him could either become the key to changing his fate—or a lethal poison that would end his life.
Without live testing, there was no data. Kagami couldn't even estimate the probability of success. But he had run out of time.
This was a gamble he had to take.
Whether he could seize control of his own destiny, live with dignity, and escape a life of being manipulated by others—all of it depended on this single vial.
Without further hesitation, Hyuga Kagami hardened his resolve and injected the gene fluid into his body.
"Ah—!"
Almost instantly, a scream of agony tore from his throat.
Pain.
Bone-freezing pain.
Heart-rending pain.
Having lived as a shinobi for so many years, Kagami believed his tolerance for pain was already high—that pain could no longer shake him.
Only now did he realize how wrong he was.
Slowly, he felt the chakra inside his body begin to dissipate.
"This is bad!"
The situation had completely slipped out of his control. Using the last of his remaining chakra, Kagami forcibly released the Summoning Jutsu, sending the One-Eyed Viper away.
The moment the snake vanished, the final traces of his chakra evaporated.
Immediately afterward, his body felt as if it were collapsing. His flesh and blood seemed to be melting away.
"Why is this happening?!"
Filled with unwillingness, Hyuga Kagami's vision went black, and he collapsed unconscious in the desert.
---
After an unknown amount of time, Hyuga Kagami slowly opened his eyes and realized he was back inside the outpost.
The captain, Mitsui Chuichi, stood at his bedside, staring at him coldly.
"What happened?" Mitsui demanded. "Why did you collapse in the desert?"
Kagami's mind was still foggy. He replied vaguely, "I… I don't know either…"
Mitsui frowned. "Were you attacked? By whom? Sand shinobi?"
Hyuga Kagami shook his head. "No. No one attacked me. Something went wrong with my body. I… I think I'm sick."
Shinobi getting sick was hardly unusual in the ninja world. Kekkei genkai users, in particular, were prone to strange and severe genetic illnesses—Kimimaro and Itachi Uchiha were classic examples.
Seeing Kagami's weakened state, Mitsui still had doubts, but he didn't continue pressing him.
After Mitsui left, Hyuga Kagami finally began carefully examining his own body.
The violent reaction after injecting the gene fluid had far exceeded his expectations. It gave him an entirely new understanding of just how dangerous activating special genetic sequences truly was.
"In the end… I survived."
Letting out a long breath, Kagami felt waves of lingering fear wash over him.
Though he didn't know the exact figures, based on personal experience alone, he was certain that surviving the activation and recombination of special genetic sequences was an event with an extremely low probability.
He had clearly felt his body on the verge of complete collapse—like being torn apart into countless pieces and forcibly stitched back together.
It was pure despair.
At the same time, it made him painfully aware of how shallow his understanding of genetics still was.
Once he calmed down, Kagami began analyzing the process based on what he had experienced.
Earlier, his body's near-collapse was clearly a reaction to the activation of dormant genetic sequences. In other words, for every missing activated sequence, his body had to undergo a full activation-and-recombination cycle.
He had been missing sixteen sequences.
Which meant that, in the desert, he had endured sixteen consecutive rounds of genetic activation and recombination.
Each one was a trip to the edge of hell.
That he had survived sixteen in a row could only be described as sheer luck.
Now, with all thirty-three special genetic sequences fully activated, Kagami could feel that his body was completely different from before—and the transformation was still ongoing.
The most obvious change was his chakra.
It was growing continuously, as if there were no limit.
Getting out of bed, Hyuga Kagami slowly walked to the mirror.
Lifting his goggles, he saw that his once-pale pupils had become almost translucent, as though the stars themselves were contained within them, shimmering with an otherworldly light.
"So beautiful…"
Even Kagami himself couldn't help but be entranced.
But as he leaned closer to examine them, a violent wave of dizziness suddenly struck. At the same time, a sharp, piercing pain flared in his pupils.
Only after a long while did the dizziness and pain slowly fade.
Leaning against the wall, Kagami steadied himself. He understood now—during the adaptation period, he couldn't use his eyes at all, not even for basic observation.
He closed his eyes and lowered his goggles once more.
Lying back down on the bed, Hyuga Kagami fell into deep thought.
The Tenseigan was still evolving.
Setting the future aside, in his current state, he was actually weaker than before.
This was no time to celebrate.
First, he had to survive this dangerous adaptation period.