The journey back to Sound Village was agony.
Sasuke's eyes burned constantly. The Byakugan's structure fighting with his natural Uchiha genetics. Not rejection—but incompatibility.
By the second day, his vision was blurring. By the third, blood leaked from his eyes constantly.
Team Taka met him at the village entrance. Suigetsu took one look at him and grimaced.
"You look like shit."
"Medical wing," Sasuke managed. "Now."
Kabuto took one look at him and immediately began diagnostic jutsu.
"Your ocular chakra network is severely inflamed," Kabuto reported, professional mask firmly in place. "The Byakugan structure is trying to integrate but your Uchiha genetics are resisting. Not full rejection, but close."
"Fix it."
"I can't fix genetic incompatibility, Sasuke. Your body needs to adapt naturally." Kabuto prepared medical supplies. "This will take time. Possibly weeks."
"How long exactly?"
"Based on cellular analysis? Two weeks minimum. Possibly a month." Kabuto injected something—pain medication. "The Hashirama cells are helping. They're accelerating the adaptation process. Without them, this could take six months or kill you outright."
"Two weeks," Sasuke repeated, lying back on the medical bed. "Fine."
"You'll need to stop using your Mangekyo entirely. No Sharingan either. Complete rest for the ocular system."
"That's not—"
"Not negotiable." Kabuto's tone was firm. "You asked me to help. This is how. Rest, or go blind. Your choice."
Sasuke closed his eyes. In darkness, at least the pain lessened slightly.
"Two weeks," he muttered. "Then I continue."
The adaptation process was worse than the Hashirama cell integration.
His eyes constantly felt wrong. Like something foreign was embedded in his skull, trying to become part of him but not quite fitting. The Byakugan's chakra structure slowly, painfully, merging with his Mangekyo pattern.
Orochimaru visited on day five.
"Kabuto tells me you're suffering."
"I'm adapting." Sasuke kept his eyes closed.
"There's a difference." Orochimaru sat beside the bed. "You absorbed a completely different bloodline family. The consequences were predictable."
"But worth it." Sasuke's hand clenched the bedsheet. "Once integration completes, I'll have access to Byakugan abilities through my Mangekyo."
"Theoretically."
"Not theoretically. I felt it. Brief moment during absorption—I could feel my degree of vision increasing." Sasuke's voice was strained but certain. "Once my body fully adapts, I'll be able to manifest those abilities."
"Assuming the adaptation succeeds and doesn't destroy your eyes."
"It will succeed. Hashirama's cells are designed for genetic integration. They'll bridge the gap between Uchiha and Hyuga bloodlines." Sasuke finally opened his eyes—the both were bloodshot, with a faint lavender hue. "How much does Kabuto estimate my chances?"
"Seventy percent for successful integration. Twenty percent for partial integration with permanent damage. Ten percent for complete failure and blindness in that eye."
"Acceptable odds."
Orochimaru smiled. "You've thought this through."
"I think everything through." Sasuke closed his eyes again.
"Cold calculation."
"It's all that matters."
On day eight, the constant burning finally began to subside. The pain was still there, but duller. More manageable.
Kabuto's scans showed progress. "The Byakugan structure is stabilizing. Your Uchiha genetics are finally accepting the foreign chakra patterns. Integration is at approximately sixty percent."
"When can I use my eyes again?"
"Give it another week. Let it complete fully." Kabuto made notes. "Rushing this could undo all the progress."
Sasuke forced himself to wait. Every day felt like wasted time. But he needed the Byakugan absorption to succeed. It was proof of concept—that his Mangekyo could collect any dojutsu, not just Sharingan.
Day fourteen. Sasuke opened his eyes.
No pain. The constant burning was gone.
He sat up slowly. Tested his vision. Normal sight. No blurring. No blood.
Kabuto entered for the morning check-up. "How do you feel?"
"Normal."
"Good. That means integration completed successfully." Kabuto ran diagnostic jutsu. "Your ocular chakra network has stabilized. The Byakugan structure is now permanently merged with your Mangeky"
"Show me."
Kabuto pulled out a chakra scan. Sasuke's eyes displayed as complex networks with two overlapping patterns—the Mangekyo spiral and something new. Byakugan's 360-degree network, compressed and integrated into the vortex design.
"Can I use it?"
"Try. But carefully. Start with just activating the Mangekyo. Don't push for Byakugan manifestation immediately."
Sasuke activated his Mangekyo. The spiral pattern glowed red.
No pain. Just... power. Clean, controlled power.
Then he pushed chakra differently. Remembered that brief moment during absorption. The 360-degree vision.
His perception exploded outward.
He could see behind him. Through the walls. Kabuto's chakra network in perfect detail—every chakra point, every pathway, every node.
But it was incomplete. Weaker than true Byakugan. Maybe thirty percent effectiveness at best. Like a diluted version.
He deactivated it. The vision returned to normal.
"It works," Sasuke said. "But it's weak."
"You absorbed one Byakugan," Kabuto pointed out. "One set of genetics. Naturally it would be incomplete. The manifestation is a fraction of full Byakugan capability."
"How many would I need for full effectiveness?"
"Impossible to say with certainty. Ten? Twenty? The more you absorb, the stronger the collective structure becomes." Kabuto made notes. "But each absorption will require adaptation time."
"How long for subsequent absorptions?"
"Your body has adapted to Byakugan genetics now. Future integrations should be faster." Kabuto estimated. "Maybe three to five days per absorption. Possibly less as your system becomes more efficient at processing foreign dojutsu."
Sasuke stood. Tested his balance. Everything felt stable. Normal.
"Then I continue hunting. Multiple Byakugan users. Build up the full capability."
"Orochimaru-sama predicted you'd say that." Kabuto handed him a folder. "He's already prepared a target list."
Of course he had.