Kenji extracted a portion of Hashirama cells from the tank and carried them to his workspace.
"Alright, let's put all that research to use."
He'd spent a long time analyzing the structure of his Swift Release core, breaking down every aspect of its design. The sealing array, the chakra circulation pathways, the conversion mechanism. He'd documented everything, creating blueprints he could adapt for other bloodline abilities.
Now came the test. Could the same principles work for Wood Release?
He started with the sealing array. Using specialized tools, he carved microscopic patterns into a diamond-shaped crystal core, each line infused with chakra to activate the seal once complete. The design was identical to the Swift Release core, a modified Four Symbols Seal that created a stable containment field for the bloodline cells.
The hardest part was integrating the Hashirama cells themselves.
Unlike Swift Release, which required only a small tissue sample, Wood Release needed significantly more biological material to function properly. The cells had to maintain their incredible vitality while being sealed, which meant the containment array had to be both powerful enough to restrict them and permeable enough to allow energy exchange.
Too much restriction and the cells would die. Too little and they might grow uncontrollably even before being installed in a puppet.
It took three attempts before he got the balance right.
The finished core looked deceptively simple. A rhomboid crystal about the size of a large marble. From the outside, you couldn't tell it contained Hashirama cells at all. The sealing work had been flawless.
"One down," he muttered, turning his attention to the puppet body waiting on his workbench.
He'd pre-assembled this one days ago. The frame was standard construction, chakra-conductive metal reinforced with specialized alloys. The synthetic skin was his latest formula, more durable than previous versions and better at mimicking human tissue. The internal chakra pathway network had been laid out with the same precision he'd used on the Swift Release puppet.
Everything was ready. All that remained was installing the core.
He opened the puppet's chest cavity and carefully placed the Wood Release core inside the designated socket. It clicked into place. Then came the tedious part: connecting each chakra pathway to the core, ensuring perfect alignment so energy could flow without interruption.
After twenty minutes of careful work, he finished the last connection and closed the chest cavity. The puppet lay motionless on the bench, inert until he activated it with his technique.
"Now for the moment of truth," he said. "Let's see if this thing explodes."
He picked up the puppet and carried it toward the back of his workshop, into a special chamber he'd constructed specifically for high-risk testing.
The room was small, maybe four meters on each side. The walls had been reinforced with Earth Release techniques, making them thick enough to withstand explosive tags. On top of that, he'd inscribed multiple layers of sealing formulas across every surface. Containment seals, suppression seals, barrier seals. If something went wrong in here, the damage would be contained.
"Better safe than sorry," he muttered, setting the puppet in the center of the room. "Blowing up my workshop would be a pain in the ass to rebuild."
He retreated to the doorway, positioned himself so he could slam the reinforced door shut if needed, and formed hand seals.
"Mind Clone Switch Technique."
His consciousness left his body and slammed into the puppet core.
The sensation was overwhelming. The Hashirama cells were incredibly active, far more so than any other bloodline he'd worked with. Wood Release chakra flooded the sealed space inside the core, filling it with raw power.
The sealing array held. There was no sign of the chakra rampage he'd been worried about.
Moving quickly, because he didn't want to push his luck, he stepped backward out of the testing chamber. His real body was still standing in the doorway. He slammed the door shut and sealed it, then returned his full attention to the puppet's perspective.
Even with the door closed, he could still sense everything the puppet experienced through their mental link. No need to stay in the danger zone personally.
Satisfied with the precautions, he decided to test the puppet's capabilities.
His hands, the puppet's hands, blurred through seals.
"Wood Release: Wood Locking Wall!"
The technique was one of the basics from the scrolls Danzō had provided. Since anyone without Wood Release couldn't use them anyway, he had been generous with sharing.
Chakra poured out of the puppet core and into the surrounding environment. The ground trembled. Cracks appeared in the reinforced floor as thick wooden pillars erupted upward, growing at incredible speed. They curved and twisted, interlocking with each other to form an arched barrier that stood solid in front of the puppet.
The barrier looked exactly like it was supposed to according to the scroll's descriptions.
"Yes!" Kenji felt a surge of triumph. Months of research, weeks of preparation, and it had actually... The puppet exploded.
Well, not literally exploded. But it might as well have.
Without any warning, the chakra inside the puppet went berserk. The entire internal chakra network lit up like someone had dumped gasoline on a fire. Energy surged through every pathway simultaneously, far beyond what the system was designed to handle.
Then the transformation started.
Thin branches burst from the puppet's surface. They erupted through the synthetic skin like needles punching through fabric, dozens of them, then hundreds. The branches grew at a horrifying rate, thickening and multiplying and spreading across the puppet's body like a cancerous growth.
Within seconds the puppet was completely covered. The wood kept growing, swelling outward, consuming the entire frame. The puppet's limbs distorted as wooden structures forced their way through joints and seams. Metal creaked and snapped. The constructed chakra pathways shattered under the pressure.
The growth didn't stop until the chakra inside the core was completely exhausted.
What remained looked like a twisted mass of wooden matter, vaguely puppet-shaped, but mostly just... weird. Warped and broken and nothing like what he'd built.
"Fuck."
Kenji immediately released the Mind Clone Switch Technique. His consciousness snapped back to his real body.
Yet, at that moment, a trace of chakra had followed him back.
His heart jumped into his throat.
In the past, when he'd controlled puppets with bloodline cores, tiny amounts of residual chakra would remain in him afterward. Those traces had been harmless, even beneficial, gradually allowing him to understand and eventually use aspects of those bloodlines himself. Swift Release and Transparent Release had both worked that way.
But this was...
He'd just watched Wood Release chakra turn a puppet into a mangled mess of twisted wood. If the same thing happened to his real flesh, blood and bones...
"Calm down," he told himself.
He closed his eyes and focused inward, searching for the strand of Wood Release chakra with his sensory abilities. It took a moment to find because it was so faint.
He watched it carefully, ready to try purging it if it showed any signs of going berserk.
But nothing happened.
The Wood Release chakra just drifted. It circulated naturally through his system, no different from his own chakra. After a few minutes, it began to blend into his body, gradually dispersing until he couldn't sense it anymore.
Just like the Transparent Release and Swift Release chakra before it.
"Okay. That amount isn't enough to cause problems. I'm fine."
Once he was certain the Wood Release puppet showed no further changes, he formed hand seals and created a shadow clone. No way was he walking into that testing chamber personally until he knew it was safe.
"Check it out," he ordered.
The clone nodded and unsealed the reinforced door. It stepped inside. But the puppet just sat there. The clone used its kunai to cut into the wooden mass. At the center, buried deep inside, it found the puppet core. The core itself was intact, the sealing array still functional. But everything around it had been destroyed.
---
"So that's what happened," Kenji said quietly. "That's why all those test subjects who got injected with Hashirama cells ended up as twisted masses of wood. It's not just that the cells transform organic matter. The Wood Release chakra itself is corrosive. It destroys everything it touches indiscriminately."
That was the key problem. The chakra didn't just affect living tissue. It attacked any material in its path, growing, spreading and consuming until nothing remained but wood. The victims in the experiments hadn't died from simple cellular transformation. They'd been torn apart from the inside as wood erupted through their bodies.
"To solve this problem, there are two approaches," he muttered, thinking it through. "First option: weaken the Hashirama cells. Dilute them until the Wood Release chakra is milder and more controllable. That would prevent the berserk growth problem."
It was the safe solution. Mix the Hashirama cells with ordinary cells, let them adapt over time, eventually producing a stable but weaker version of Wood Release. Exactly what had happened with Yamato in the original timeline.
"The problem is, that tanks the power. Yamato's Wood Release was useful for construction and restraint, but combat-wise? It was barely stronger than regular elemental jutsu. Not what I'm going for."
Still, he didn't dismiss the idea entirely. A weakened Wood Release puppet could serve as proof of progress for Danzō. The old man had invested a lot of resources into this project. He'd want to see results. Giving him a functional but limited prototype would keep him happy and willing to continue providing materials.
Plus it would be easier to maintain the fiction that Kenji was still working on the "real" version. Keep Danzō invested, keep the supplies flowing, and use those resources to fund his own research.
"Yeah, that works as a backup plan."
Which brought him back to the core problem: how do you contain Hashirama-level Wood Release chakra without it destroying everything?
"Regular materials can't handle the corrosion. Even chakra metal gets torn apart. So do I need to make the entire puppet from pure chakra metal? Would that even work?"
That approach had problems. Pure chakra metal was expensive beyond belief. He'd burn through Danzō's entire budget making one puppet, and there was no guarantee it would actually resist the Wood Release chakra. The test he'd just run suggested even reinforced alloys couldn't handle it.
His clone shifted position, and something caught his attention.
The wooden structures covering the puppet's surface. They'd been generated directly by Wood Release chakra. The clone reached out and touched one of the branches.
It was hard, dense, and solid.
An idea was forming.
"Regular materials can't withstand the corrosion. But what if I use materials that the Wood Release chakra itself created?"
Wood Release chakra generated wooden structures. Those structures were products of the chakra, byproducts of its transformation ability. Which meant they might not be seen as "foreign matter" by the chakra.
If he used wood created by Wood Release chakra as the base material for the puppet, maybe it could withstand further exposure to that same chakra. Maybe the two would form a symbiotic relationship instead of the chakra destroying the structure.
"It's worth testing."
He ordered his clone to carefully dismantle the wooden structures covering the puppet's surface. Cut them away from the ruined frame, sort them by size and density, preserve them properly. He'd process those materials using his standard puppet-making techniques, craft a new frame from Wood Release-generated wood, and try again.