Chapter 228 – Fusion Surgery
The experiment had to begin—sooner was always better.
If not for the uncertainty of when exactly the Hyūga clan would release Ayaka, Kei would have started the procedure on his own long ago. The fusion period for the Eternal Mangekyō Sharingan was lengthy, and Kei didn't want to waste a single moment.
After delegating his current tasks to Imai Kenta and Uchiha Kawa, Kei brought Hyūga Ayaka down into the underground laboratory.
The lab was quieter than usual. With Kakashi needing reinforcements, several personnel had been reassigned. Still, the defensive measures in this area were airtight. Kei and Fugaku had long since ensured that no outsider would stumble into their most secret facility.
They entered the chamber where Uchiha Shuu and Uchiha Yuu were kept. The brothers remained submerged in nutrient fluid inside their life-support pods, looking for all the world as if they were peacefully asleep.
Kei and Ayaka drained the pods and carefully laid the brothers out on operating tables. Ayaka then attached an array of monitors and stabilizers to Shuu's body.
When everything was ready, she asked quietly:
"Do I remove Yuu's eyes directly?"
"Yes. Extract them carefully—make sure the eyes remain intact. Once it's done… end him." Kei's voice was steady.
Yuu's body had served its purpose. His continued survival had meaning only as a container for the Mangekyō. His consciousness had been erased long ago. In truth, the man had already died.
Kei had, in his own way, honored their deal. He had left Yuu's lover and family untouched. Allowing the man to linger in this hollow existence was a cruelty. Death would be a mercy. And soon enough, his brother Shuu would follow him.
Ayaka gave a silent nod. Without another word, her hands lit with the soft glow of green chakra as she pressed them over Yuu's eye sockets.
The extraction was quick. She didn't even need to activate her Byakugan. In less than five minutes, she held in her hands a pair of crimson eyes, patterns swirling ominously across their surface. Even severed from their host, they radiated a suffocating aura—staring too long threatened to pull one's mind into their depths.
Ayaka's face tightened. These eyes felt… wrong. The thought of the power they contained, wielded by someone in full control, was terrifying.
Taking a breath, she shifted her glowing hand down to Yuu's artery. His body convulsed once, then fell still. No breath. No heartbeat.
Kei didn't bother to glance at the corpse. His gaze stayed locked on the eyes. Yet, another thought intruded.
The fusion of the Eternal Mangekyō worked by one pair devouring the other's ocular power. But… would the donor's abilities remain, or be erased?
He recalled how Sasuke, even after receiving Itachi's eyes, never displayed Tsukuyomi. Amaterasu persisted, but only through some strange "transference seal."
If so, then retaining the absorbed techniques wasn't guaranteed. Kei frowned. Ultimately, though, it didn't matter. These eyes weren't his. If the donor's powers were lost in the process, then so be it—he still profited.
A shame about Yuu's Susanoo-enhancement, perhaps. But it wasn't truly compatible with him anyway.
"My own Susanoo is already progressing," Kei murmured to himself. At his current stage, his Mangekyō could sustain the second form, while his base Sharingan could barely hold the first. It was enough, for now.
And besides, Shuu's eyes promised plenty. When forced to awaken his Mangekyō, under the trauma of his brother's fate, Shuu's eyes had manifested two techniques:
Amaterasu, the black flames of inescapable destruction.
And another ability Kei had never heard of before—Kagutsuchi-no-Mikoto's counterpart: Homura-no-Mikoto.
While Kagutsuchi granted control over Amaterasu's shape and form, Homura amplified it—magnifying its heat, range, and sheer destructive power.
Kei could imagine the devastation. Where Itachi once scorched half a forest with Amaterasu, Shuu's ability could have incinerated the whole woodland, perhaps more.
"Let Fugaku handle that kind of fire," Kei thought dryly.
Turning to Ayaka, he said, "Now comes the transplant. It'll be difficult—the fusion of two Mangekyō is no simple eye swap. Are you ready?"
Ayaka's expression remained calm, though her voice was measured.
"I'll do everything I can. But don't expect perfection. I've attempted this only a handful of times… and succeeded once."
She wasn't lying. Her experience with ocular fusion was extremely limited.
Though Kei had briefed her beforehand, Hyūga Ayaka rarely had real opportunities for practice.
Kei nodded. He understood her limitations, but there wasn't much he could do about it. Ayaka's primary focus had always been on genetics and cellular research. That she could even assist in a transplant like this was already valuable.
"Then let's begin." Kei's Sharingan spun open as he added calmly, "I'll support you. I've studied the Uchiha ocular transplantation arts, but a procedure like this… I wouldn't dare attempt it alone."
"I understand." Ayaka's tone was even as she moved to Shuu's side, carrying Yuu's freshly removed Mangekyō eyes.
The fusion was far trickier than a mere transplant. Kei had once considered using a Transference Seal—extracting Yuu's ocular power and sealing it into Shuu's eyes. But as his status grew, Kei gained access to old clan records.
It had been attempted before. The results were failures.
The seal could transfer fragments of ocular power, even abilities—but never true fusion. Worse, the seal itself became an obstacle, preventing the natural devouring process. And if the seal was undone, the stored power could leak or even explode.
Even with brothers as donors, the risks were unacceptably high. Kei had no intention of gambling with his prize.
This was also one of the reasons Fugaku had chosen compromise after Kei revealed his Mangekyō. It wasn't only that Fugaku might lose in a fight—it was that Kei's eyes were completely incompatible with his own. Even if Fugaku stole them, he could never evolve them.
As for a simple transplant? Pointless.
Mangekyō power resides in the eyes, while the body is only a vessel. If swapping eyes alone worked, Madara and Izuna would both have gained Eternal Mangekyō. The two brothers could've fought Hashirama side by side with twin avatars, and history would have taken a different course.
The same logic applied to Itachi and Sasuke. If a swap alone worked, after Sasuke awakened his Mangekyō, Itachi could have revealed the truth, they'd exchange eyes, and the whole tragic mess would have been avoided.
…Though Itachi's death wish would never have changed. The sins he bore were already too heavy—death was the only release.
As for his current condition, Kei no longer kept track.
The last time they spoke, Kei had deliberately told him things from a perspective the boy couldn't yet grasp. Since then, he hadn't seen him. Fugaku certainly wasn't inclined to bring up his eldest son, and Kei had no interest in asking.
Better not to see him at all. As long as Kei stood in his way, the boy could never stir up any waves.
Brainwashing Itachi had never been Kei's choice. For him, it was better to solve problems at their root rather than merely treat the symptoms.