The nights following Amanai's initial training session fell into a predictable pattern. Amanai would arrive after sunset, drill Muzan on basic shinobi skills for several hours, then leave before dawn. The curriculum covered fundamental combat techniques: how to throw shuriken with accuracy, proper kunai grip for both stabbing and throwing, basic taijutsu stances and strikes designed to disable rather than kill.
What Amanai conspicuously avoided teaching was ninjutsu. He'd demonstrated the twelve hand seals on that first night and never mentioned them again. No explanation of how to convert chakra into elemental techniques, no discussion of specific jutsu, nothing beyond the basic theory. The omission was deliberate and Muzan understood why. Ninjutsu represented the Uchiha clan's real power and they wouldn't share that knowledge with someone whose loyalty remained unproven.
Muzan spent the daylight hours confined to his tent, using the time to explore his transformed body's capabilities in greater detail. The transformations he'd used in combat against the Kamizuru shinobi had been instinctive responses driven by survival needs, but now he approached them methodically.
He discovered he could manipulate his flesh with surprising precision. His arms could stretch and thin into whip-like appendages covered in bone protrusions sharp enough to cut through wood when he tested them against the tent's support poles. The extended limbs were pink and distorted, their structure more organic than mechanical, but they responded to his will with perfect control. Alternatively, he could compress and harden the flesh of his forearms into blade-like structures that resembled white bone with a cutting edge along one side. Each transformation consumed a small amount of chakra when initiated but required no additional energy to maintain afterward.
The transformations were all variations on the same fundamental ability to reshape his body's structure according to his will. After considering various options, he settled on thinking of this core power as biokinesis. The term was clinical but accurate. He was manipulating biological tissue at a level that shouldn't be possible for any normal organism.
The examination also revealed something else. His transformed structure bore similarities to what he remembered of the ancient tree from the ritual that had changed him. The tree had possessed multiple cores and distributed consciousness across its entire mass. If that parallel held true, it suggested he might be able to create other beings like himself by introducing his cells into normal humans.
Muzan immediately decided not to test that theory. Creating more demons when he barely understood his own condition would be reckless. He needed knowledge and control before experimenting with abilities that could have unpredictable consequences.
The hunger in his chest continued to build steadily with each passing day. Every transformation and every use of his regeneration depleted his chakra reserves, and the depletion triggered cellular demands for replenishment through feeding. He'd managed to suppress the worst of the urges so far but he knew he would need to feed again soon. The question was how to do it without exposing his nature to the watching Uchiha.
On the fifth night after his training began, Amanai arrived at his tent with a different expression than usual. His face was set in hard lines and his posture carried tension that suggested something significant had changed.
"No training tonight," Amanai said as he stepped inside. "The camp is mobilizing. We're moving to the frontlines."
Muzan looked up from where he'd been sitting. "The frontlines?"
"This was always a reserve force," Amanai explained. "We just received orders to deploy. There's a major engagement developing near the border between the Land of Fire and the Land of Rivers. The Senju broke through our eastern defenses and they're threatening to cut our supply lines. If we don't reinforce the position now, the entire theater collapses."
He crossed his arms over his chest. "We leave in three hours. The march will take all night and we should reach the battlefield area by dawn. Pack whatever supplies you need."
"What will my assignment be?" Muzan asked.
"Given your sunlight limitation, you're being assigned to my squad permanently," Amanai said. "We handle reconnaissance, sabotage, and assassination operations that typically occur during darkness. You'll be able to operate without the sun being an immediate problem. Stay close to me and Toshiro during operations and follow orders precisely. If you attempt to flee, I have authorization to execute you. If you perform well in combat, you might start earning some actual trust from the clan leadership."
He paused and his expression hardened further. "The Senju aren't training exercises or bandits. They're among the strongest shinobi in the world and they've been fighting this war as long as we have. They'll kill you without hesitation if you give them an opening. One mistake in combat and you're dead before you realize what happened."
"Understood," Muzan said.
"Do you really understand?" Amanai's eyes narrowed. "You've absorbed training quickly over the past few days but there's a difference between learning techniques in a safe environment and using them when someone's actively trying to kill you. Combat is chaotic and brutal. People die in seconds. You need to be ready for that reality."
Muzan met his gaze without responding. What could he say that would be convincing? He'd already killed and eaten five shinobi in brutal close combat. He understood exactly how violent and messy fighting could be. But admitting that would raise questions he couldn't afford to answer.
Amanai studied his face for another moment, then nodded. "Three hours. Be ready to move."
He turned and left the tent, pulling the flap closed behind him.
Muzan sat in the darkness after Amanai departed and considered his options. He could leave right now if he chose to. He'd learned enough about the geography during his training sessions to know he was currently in the Land of Fire. The Land of Iron lay to the north and west, probably a week's travel on foot. With his enhanced speed and endurance, he could cover that distance in half the time if he pushed himself.
But leaving now felt wrong for reasons he couldn't fully articulate. The Uchiha had kept him under constant surveillance and clearly didn't trust him completely, but they'd also provided shelter during his vulnerable daylight hours and taught him fundamental skills for surviving in this world. The training had been basic but valuable. Walking away without reciprocating in some way would leave an obligation unfulfilled.
He would fight with them in this coming battle. Repay the debt of their instruction with his combat abilities. Then once the engagement ended and his obligation was satisfied, he would leave and make his way back to the Land of Iron. The plan was straightforward enough.
Muzan stood and began checking the equipment the Uchiha had provided him. The clothing was standard issue for the clan: dark blue shirt and pants designed for ease of movement, basic armor plates strapped to his forearms and shins for protection against slashing attacks, and a weapons pouch secured to his right thigh containing kunai and shuriken. He tested how the armor fit and made minor adjustments to the straps until everything felt secure.
The three hours passed more quickly than he expected. Outside his tent, the sounds of the camp transformed from its usual nighttime quiet to organized chaos. Voices called out orders. Equipment clanged as it was packed and loaded. Fires that had been burning low were extinguished completely, plunging the area into near-total darkness broken only by a few shielded lanterns.
When Muzan emerged from his tent, he found the entire camp in motion. Nearly thirty shinobi were forming into organized groups, each person performing final checks on their weapons and gear. The atmosphere was focused and tense, everyone moving with purpose toward a specific objective.
Toshiro appeared beside him, materializing from the shadows with the flickering movement Muzan had come to recognize as a basic speed technique. "This is your first real battle, right?"
"Yes," Muzan confirmed.
"You're lucky you won't be on the main frontline where the Senju and Uchiha clash directly," Toshiro said. "But assassination and sabotage missions carry their own risks. Enemy shinobi on those operations are usually elite specialists. Stay behind Amanai-san and me during engagements. Don't try to be impressive or take unnecessary risks. Just follow orders, stay alive, and learn from watching us work."
"Understood."
Amanai approached wearing full combat loadout that included additional armor plates across his chest and back, multiple weapons pouches strapped to both thighs, and a longer sword secured diagonally across his back where he could draw it quickly with his right hand. His expression was completely neutral now, all traces of his earlier intensity replaced by professional calm.
"Form up," Amanai ordered.
Muzan joined the formation, positioning himself in the third rank between two other Uchiha shinobi who acknowledged him with brief nods. Everyone stood in precise rows and columns, maintaining enough space to move freely but staying close enough for rapid communication.
A figure appeared at the front of the formation and Muzan recognized Lord Urashi stepping onto a raised platform constructed from stacked supply crates. The clan leader wore full battle armor marked with the Uchiha crest, and his presence commanded immediate attention from everyone assembled.
"Uchiha!" Urashi's voice carried across the camp with authority. "The Senju have broken through our eastern defensive line and are advancing toward our supply routes. If those routes are severed, our forces already engaged further north will be cut off and destroyed. We cannot allow that to happen."
He paused and activated his Sharingan, the red glow of his eyes visible even from a distance in the darkness. "We march to the frontlines tonight to reinforce our clan members already fighting there. We will drive the Senju back and restore our defensive perimeter. Show them why the Uchiha clan is feared across every nation. Show them the strength that has made us one of the most powerful shinobi forces in history!"
The assembled shinobi responded as one, their voices merging into a single word that echoed through the trees: "Uchiha!"
Urashi nodded once. "Move out!"
The formation began advancing immediately, breaking into smaller groups that spread out as they entered the forest. The movement was controlled and professional, each squad maintaining its own spacing while staying close enough to support adjacent units if needed. Despite the number of people moving through the undergrowth, the sound was minimal. Feet found purchase on solid ground automatically and branches were moved aside silently.
Muzan stayed close to Amanai and Toshiro as instructed, matching their pace and mimicking their careful placement of each step. His enhanced senses picked up details the others might have missed: the subtle shift in air currents as bodies moved past, the faint scent of weapon oil and nervous sweat, the controlled breathing of shinobi preparing mentally for combat.
The march continued through the night at a steady pace that covered ground quickly without exhausting the shinobi before they reached their destination. Muzan's transformed body didn't tire from the exertion but he maintained the appearance of normal endurance to avoid drawing attention.
As they moved deeper into the forest, Muzan's thoughts turned to what waited ahead. He was about to enter a real battle between two powerful shinobi clans who'd been fighting for generations. People would die, probably in large numbers. He would be expected to kill Senju shinobi if they encountered them.
The prospect didn't disturb him as much as it probably should have. He'd already killed five people and consumed their flesh. Adding more deaths to that total wouldn't change what he'd become. And if killing enemy shinobi satisfied his obligation to the Uchiha while also providing opportunities to feed and replenish his chakra, that would solve multiple problems simultaneously.
The hunger stirred in his chest at the thought of fresh blood and flesh. He forced it down and focused on maintaining his pace with the formation.
Dawn was still several hours away when they finally stopped. Ahead, the forest opened onto cleared terrain where Muzan could see the signs of recent combat: scorched earth from fire techniques, craters from earth manipulation, trees split and toppled from explosive tags.
The battlefield was close now. And with it, the test of whether Muzan could maintain his cover while fighting alongside the Uchiha against their ancient enemies.