Seven days had passed since the chaotic night of the ambush.
The atmosphere in the Konoha camp had shifted dramatically. The frantic desperation of the triage wards had been replaced by the orderly, if somewhat dull, routine of a long-term occupation.
Tsunade had departed three days ago, taking the convoy of critical patients—including Nawaki—back to the safety of the village. With her went the immediate pressure on Ren's shoulders.
Replacing her command was Kato Dan. The blue-haired Jonin had arrived with five hundred fresh troops and a full corps of medical ninja. With the staffing shortage resolved, Ren was no longer required to pull double shifts. For the first time in weeks, he had time to breathe.
And time to teach.
"Focus, Mikoto. Don't force the chakra; guide it."
In a quiet corner of the camp, under the shade of a large rock formation, Ren sat cross-legged across from Mikoto Uchiha. Between them lay a shallow basin of water with a half-dead fish floating on its side.
Mikoto frowned, beads of sweat forming on her forehead. Her hands hovered over the fish, glowing with a flickering green light.
"It's difficult," Mikoto murmured. "My chakra wants to be sharp. It wants to burn. Turning it into something soothing... it feels like trying to hold water in a sieve."
"That's the Uchiha nature," Ren corrected gently. "Our chakra is naturally potent and inclined toward Yin Release. Medical ninjutsu requires Yang Release—physical vitality. You have to actively suppress the 'edge' of your chakra."
Mikoto took a deep breath, closing her eyes. She slowed her flow. The flickering green light stabilized, becoming a steady, soft hum.
In the basin, the fish's gills twitched. Then, with a splash, it righted itself and swam vigorously around the bowl.
"I did it!" Mikoto beamed, her usual composed demeanor breaking into genuine excitement.
"Good," Ren nodded. "Most Uchiha take weeks to grasp the conversion. You have a knack for control."
Mikoto wiped her hands, looking at him with admiration. "I want to be useful, Ren. If I can heal, I can support you and the clan better."
"You're doing great," Ren encouraged her. "Keep practicing. Once you can keep one alive for an hour, we'll move to cellular activation."
Once Mikoto left to practice, Ren turned his attention to the small work table he had set up in his tent.
Scattered across the surface were scraps of parchment, vials of ink mixed with chakra-conductive dust, and a few failed prototypes.
He sat down, his expression shifting from teacher to researcher.
'Seven days,' Ren thought, checking his internal status.
[Quincy Compatibility: 69%]
'Progress is steady. But today... today is about the tag.'
He picked up a blank scroll, his mind drifting back to a conversation he had with his mother, Kaori, just two days prior while they were changing bandages in the ward.
[Flashback – Chapter 13]
"Mom," Ren whispered, moving to the next patient. "About my idea. The Healing Tag."
Kaori didn't stop working, her hands glowing green. "What about it?"
"Why hasn't anyone done it?" Ren asked, genuinely puzzled. "We have Explosive Tags. We have Sealing Tags. Why don't we have a tag that just releases a burst of Yang Chakra to close wounds? It would solve this shortage instantly. Tsunade wouldn't have to run around like a headless chicken."
Kaori sighed, wiping sweat from her forehead with her sleeve.
"It's not that simple, Ren. Think about the nature of chakra."
She pointed to an Explosive Tag on a nearby guard's pouch.
"Explosive Tags use Fire or Lightning nature. Those energies are volatile. They want to expand. They want to destroy. You just stuff them in the paper and put a weak lock on them. When the lock breaks, boom. Easy."
She then pointed to the gentle green glow on Ren's hands.
"Yang Release—medical chakra—is different. It's life energy. It's fluid. It requires Intent."
"Intent?"
"To heal a wound, you have to tell the cells what to do," Kaori explained, knitting a deep gash on a patient's leg. "You have to guide the flesh to reconnect. If you just seal raw Yang chakra into paper and release it... it won't heal. It will just disperse into the air as green mist. Or worse, it might cause tumors by stimulating cells randomly."
Ren paused. That made sense. Explosions are chaotic. Healing is orderly. Paper couldn't 'think'. It couldn't guide the chakra.
"So," Ren murmured, "the difficulty isn't storage. It's Programming."
"Exactly," Kaori nodded. "You would need a sealing script so complex it acts like a brain. It would need to tell the chakra: 'Find damaged tissue. Stimulate mitosis. Stop when healed.' No Seal Master has ever figured out a formula that small and cheap."
[Present Time]
Ren stared at the blank paper.
To a normal ninja, writing a "brain" into a piece of paper was impossible. The complexity of the script would require a scroll five meters long, making it useless in battle.
But Ren had a cheat.
He closed his eyes, centering himself. When he opened them, his right eye shifted. It wasn't the Sharingan. It was something deeper, a manifestation of his transmigrated soul's mental power.
[Omoikane: Active]
His right eye wasn't for simple tasks like healing a cut. It was a super-computer.
Ren looked at the ink. Omoikane began to simulate millions of chakra pathways instantly. It visualized the biological process of healing—platelet activation, fibrin generation, tissue knitting. It broke these biological processes down into mathematical algorithms.
'I don't need a five-meter scroll,' Ren analyzed, his eye spinning with data. 'I need to compress the instructions into a high-density fractural seal.'
His brush touched the paper.
He didn't just write; he downloaded the code from his mind onto the paper. The kanji were microscopic, layered on top of each other in a multidimensional array.
'But the chakra will still want to disperse,' Ren realized. 'The script gives the order, but the energy needs a shape.'
He engaged his Quincy ability.
'Reishi Manipulation.'
Ren didn't just pour chakra into the ink; he pulled the invisible Reishi from the air, weaving it into the ink as he wrote. He created a rigid spiritual "skeleton" within the seal. This structure would hold the Yang chakra in a specific shape—a medical matrix—even after it left the paper.
He finished the final stroke.
The tag didn't just glow; it pulsed with a heartbeat.
"Done."
Ren picked up a kunai and, without hesitation, sliced a shallow three-inch cut across his left forearm. Blood welled up.
He picked up the prototype tag and slapped it onto the wound. He channeled a spark of chakra to activate it.
Hummmm.
There was no explosion. No mist. The tag dissolved into a cohesive, rectangular patch of green light. The light didn't float away; it adhered to the skin, driven by the "Intent" Omoikane had programmed into it and held together by the Quincy Reishi structure.
It scanned the damage. It executed the repair code.
In three seconds, the light faded.
Ren wiped the ash away. The cut was gone. Not even a scar remained.
"Success."
Ren leaned back, exhaling sharply. The combination of his unique mental processing power (Omoikane) to write the "brain," and the Quincy ability to build the "body" of the jutsu, had solved a problem that had stumped sealing masters for decades.
'With this, the Uchiha don't just have weapons,' Ren thought, a cold, calculating smile touching his lips. 'We have the monopoly on life. And I have the patent.'
Just as he was contemplating the political storm this piece of paper would cause, the tent flap opened.
"Ren," his father's voice cut through his thoughts.
Ren immediately covered the prototype tag with a blank scroll. "Dad?"
Satoshi stepped in, looking serious. He was fully geared up.
"Kato Dan has summoned the squad leaders. There's movement on the border again. You're requested at the command tent."
Ren stood up, the researcher vanishing, replaced by the soldier.
"Understood."