Cautious Eyes: An Uchiha's Path

Aya Hyuga's experimental procedures required a vast and secure facility, and Uchiha Kai wholeheartedly agreed. Undertaking such high-risk procedures made sense only if the potential gains justified it—and in this case, they certainly did. Still, there were safer, more orthodox methods available. So why take the risk?

Regardless, Kai had already spoken with the Hyuga clan and secured temporary permission for Aya Hyuga to remain in the Uchiha sector. While she wasn't fond of the oppressive underground lab's dim lighting, Kai arranged for her to use a private medical room at the Konoha Military Police headquarters. The Uchiha Police Force compound was spacious and well-guarded. Even if Kei didn't always remain on-site, Kenta Imai was there to ensure Aya was treated with dignity and safety.

As for Uchiha Osamu's fusion process, Kai could only wait. Neither he nor Aya stayed overnight, but Uchiha Fugaku had posted trusted operatives to monitor the subject. They were instructed to collect biological data with caution, and all findings would be transparently reported to both Kei and Fugaku.

Despite publicly granting Kai the authority to oversee the Mangekyō experiment, Fugaku remained attentive. After all, these eyes weren't just any Sharingan—they had the potential to rival the Mangekyō of Uchiha Madara himself.

The only concern was Kai's crude method—surgically implanting two sets of Mangekyō Sharingan into a single host. Fugaku refrained from criticizing him openly. He had promised Kai his support and intended to keep that promise. Still, part of him secretly hoped the experiment would fail. That would avoid the political and ethical storm brewing beneath the surface.

Kai, of course, had no idea what Fugaku was thinking. He only knew that the fusion process was progressing at an agonizingly slow pace. Aya conducted daily Byakugan inspections, but even after a full week, there were no signs of cellular synchronization between the eyes. If Kai hadn't noticed a faint chakra resonance forming in the ocular sockets, he might have terminated the trial.

"It seems I have no choice but to stimulate the fusion with Mangekyō chakra itself," Kai muttered. "This delay is intolerable. Maybe our procedure was too primitive. We're relying on instinct alone."

Since Uchiha Osamu's consciousness had been suppressed, his body couldn't actively guide the fusion—only his cellular memory could.

According to their estimates, the fusion could take six months or more—far too long. In that time, the Nine-Tails could break free, or worse.

Fortunately, Kai had already considered refining his own chakra foundation to reduce Mangekyō strain. Aya had completed preliminary studies on medical ninjutsu involving cellular fusion, and she now had some actionable data.

"Based on your DNA samples and the donor tissue you gave me, the overall compatibility rate is merely acceptable," Aya said bluntly, scanning her clipboard. "Out of over a thousand in vitro simulations, only 10% showed any positive reaction. Full cellular fusion occurred in around 40% of those cases. But the rate of autoimmune rejection—backlash—is around 28%."

Kai frowned. "Not great. Is there any way to suppress the phagocytic response or reduce rejection rates?"

"Possibly," Aya replied. "We could attempt in vitro fusion and then reinject the compatible cells. It's inefficient, and your body may still reject them—but it's safer."

Kai sighed. "A human body has trillions of cells. How many could we realistically process this way?"

"It would take years," she admitted. "But if we use blood as a carrier, it might improve integration—although the rejection risk increases. Still, once your immune system adapts to the first injection, the next rounds should become progressively easier."

"Fine. Let's try one injection per week," Kai decided. "Monitor me closely."

Aya nodded. "I will. But don't misunderstand this for compassion. You're the only person who can help me escape my fate within the Hyuga clan. Our agreement stands: helping you means helping myself."

Kai glanced at her, then gave a wry smile. She was done playing mind games—now she relied on honest exchange. He respected that.

Her assistance had already proven valuable, and Kai was considering how to reward her when the time was right. Perhaps he'd eventually share secrets of the Ōtsutsuki—like the pathway leading to the moon. Perhaps he'd even fabricate an ancient artifact to "prove" the Hyuga clan's lunar heritage. But those revelations could wait until his power surpassed even the Tenseigan's significance.

He gave her a nod, and so their first round of experimentation officially began.

Elsewhere in Konoha, within the Hokage's office, a storm was brewing.

Sarutobi Hiruzen sat with his old advisors—Koharu Utatane, Homura Mitokado, and Shimura Danzo. The village's power core for decades, these four had shaped Konoha's policies in both war and peace.

"Orochimaru's gone too far this time," Danzo growled, slamming a report onto the desk. "My men only discovered his hidden lab by accident. If we hadn't, we'd still be in the dark."

"And who do you think encouraged him to pursue this line of research?" Hiruzen retorted coldly. "Wasn't it your shadow ops who funded his earliest human trials?"

"Enough!" Koharu snapped. "Hiruzen is no longer Hokage, Danzo. Blame won't solve anything."

"Correct," Homura added. "Right now, we must deal with the aftermath of Orochimaru's actions—and begin planning for the Fourth Hokage's succession. And more urgently… the Uchiha situation."