"Fusion Protocols"
Uchiha Kai had struck what seemed like a promising deal.
Aya Hyuga—with her piercing Byakugan—had proven herself impressively resourceful. Such a collaboration was rare to come by, and for now, she was undeniably reliable.
It had only taken a few days before she presented a detailed experimental report to him.
During that time, Uchiha Kai had avoided using his own serum—an unstable mixture of his cells and the mysterious white matter. He had been waiting for something more concrete before making a final decision.
"The report is ready," Aya said, looking visibly fatigued, though she still carried herself with her usual composure.
"It's not looking great," she admitted. "We tested on a thousand samples. There are only two consistent outcomes. You'll need to be prepared."
"Two outcomes?" Kai echoed. He took the report from her, frowning slightly as he swatted away a buzzing fly—an annoying presence he had no time to deal with.
Bowing his head, he began reading. What he saw made his brow furrow deeper.
Only two significant results:
20% of samples showed successful fusion.
10% were completely unresponsive.
A staggering 70% experienced severe negative reactions.
No wonder Aya said there were only two real outcomes.
Ten percent could be ignored. But the twenty-percent success rate was massively overshadowed by the seventy percent failure rate. The numbers screamed one thing: this experiment had largely failed.
"What caused this?" Kai asked, his expression darkening. "A failure rate that high—it's insane."
Aya responded calmly. "Because those cells are more advanced than yours. And more importantly, they're not compatible. They were activated by someone else's Mangekyō."
"Someone else's eyes…" Kai muttered.
Now he understood. The cells harvested—likely from another Mangekyō user—couldn't synchronize with his chakra or ocular powers. The incompatibility wasn't just physical; it was spiritual, too.
They weren't from a blood relative. They didn't resonate with his unique chakra signature. After fusion, they rejected his body. Instead of enhancing him, they began attacking him from within.
Higher-grade cells could overwhelm his own, triggering internal rejection. In the best-case scenario, this would mean total blindness. In the worst-case—death.
It was unacceptable.
Ironically, the cells derived from White Zetsu—though also highly advanced—had a higher compatibility rate with his body. The fusion results with them had shown only minor negative reactions.
Kai clenched his fists. He'd come so far. Was this really the wall he was meant to hit?
Just as he was about to toss the report aside, something clicked.
Wait. Both the White Zetsu cells and his own had fused successfully before. What if those fused cells could serve as a bridge?
"You said these cells were incompatible with me directly," Kai began. "But what if I use my previously fused cells as an intermediary?"
Aya blinked, caught off guard. "You mean a secondary fusion? Taking the already stable fusion of your cells and White Zetsu cells and introducing the Mangekyō samples into that mix?"
"Exactly."
Aya thought about it. "There's no precedent, and no current data… but theoretically—it's worth trying."
These Mangekyō cells were too aggressive for direct fusion, but if paired with already-stable hybrid cells containing Kai's DNA, the odds of rejection might be reduced. The white matter might act as a buffer, regulating the aggressive tendencies of the Mangekyō cells.
Aya's eyes lit with cautious excitement. "The serum you gave me—it's purer than what we extracted from Uchiha Osamu. The successful fusion with it is leagues better than this second experiment. If we can layer the fusion again…"
Kai nodded. "Then let's do it. We've already come this far. If we stop now, all of this was for nothing."
Aya didn't hesitate. "I just happened to extract new samples today. We can start immediately. What do we do with the other test batches?"
"Discard them, or mix them in if it's too much trouble. Not worth the time," Kai said flatly.
"Alright. If this fails, it'll be a waste of blood… but the risk is acceptable."
Aya retrieved the stabilized fusion serum from cold storage, thawed it, and began the second-stage experiment. Kai stood back, unable to assist, forced to wait silently.
Flies buzzed in the damp underground lab, irritating him more than usual. Unlike Orochimaru's pristine facilities—funded and hidden by Konoha's black ops—Kai's base was makeshift. The air was still, and somewhere nearby, perhaps, a body hadn't been properly dealt with. Likely Uchiha Yu's.
He sighed and waited.
But then Aya looked up—faster than he expected. Her expression was unreadable, her eyes fixed on the blood sample.
Kai's heart skipped a beat.
"You're ridiculously lucky," she finally said, her voice tinged with disbelief.
"The fusion rate was 77%. And the rest didn't reject—it was more like an ineffective reaction. The Mangekyō cells got absorbed. It's not a failure—just neutralized."
"Seventy-seven?!" Kai's eyes widened. "That's… insane. Are you sure?"
Aya shot him a look. "You can repeat the test if you don't trust me. But the results are solid."
Kai stepped forward, staring into the vessel of blood.
Aya continued, "It seems that once all the components are high-grade—your cells, the white matter, and the Mangekyō-derived cells—they begin resonating. There's a faint but detectable new energy forming in the fusion. They're not just stable—they're attracting each other."
"A new power…" Kai whispered, eyes shining. "This is the real path forward."
He straightened up, tension draining from his shoulders. "What happens if I inject this into myself?"
"There'll be some reaction," Aya said cautiously. "There always is. But since a large portion of the serum carries your genetic signature, your body should adapt far more easily."
Kai nodded slowly. "So this… this is a success."