He was given like three weeks to take a break and recover, so he was planning on using that time for his experiment.
He had gotten plenty of Bijū chakra from the One-Tail. The beast probably didn't notice it, since its chakra healed afterward and all—probably thought the reason it felt weaker was due to the boy's seal and all, not because he was draining it dry of its chakra.
So, Seijuro made a shadow clone, used Kyōka Suigetsu on it, while his real self slipped away. He had shit to do and experiments to run, so he would use this time wisely.
In terms of strength, he should be at elite Jōnin level—Kage level if he started using Bijū chakra.
Hm. Entering First Stage Mode for the Seven-Tails' chakra, Seijuro proceeded to fly... yes, fly toward his destination.
Flying was a new feeling. Hm. He liked it. It felt natural, as if another piece of him had returned—as if he was never meant to be bound to the earth like this. The shackles of this planet were never meant to bind him.
He flew for a long time.
He got roughly six kilometers away from the battlefield—more closely, from the Konoha camp.
From there, he found a spot in the forest. Using Earth Style, he created a hole in the floor. Using Doton once more, he crafted himself an underground base.
Once inside, he began adding the final details to make it feel more like a scientific base.
After taking out his storage scroll, he began adding the bare essentials—you know, like torches, water, and so on.
The shit, really.
Eventually, he managed it.
The room lit up.
A hidden lab. Modest, but efficient. The walls were lined with scroll-sealed tools, vials, diagrams of Jinchūriki physiology, and sketched calculations.
Seijuro stepped in, placing a satchel on the counter.
Inside: a vial of Shukaku's chakra, a small jar of Shukaku-infused sand, a blood sample from Bunpuku, and a sample of Tsunade's blood—the last acquired during a recent medical exchange, not theft. (Okay, semi-theft. But she'd be fine. Probably.)
He pulled on sterile gloves, activated a cooling barrier, and got to work.
HOUR ONE: THE SQUIRREL
A wild squirrel, snatched from the surrounding forest—chirpy, innocent, stupidly curious.
Seijuro placed a diluted trace of Shukaku's chakra near its skin. The results were... explosive.
The chakra immediately overwhelmed the creature's system, its eyes going wild, body tensing unnaturally as if something ancient had tried to crawl inside a frame far too weak to handle it.
It took ten seconds before the squirrel exploded into a thousand little pieces. Its tiny little body was unable to wield so much power.
Well, that was good to know.
"...Noted."
He did try several more vials, but no luck there. He did manage to create a powerful squirrel, though—its power could rival a Genin.
That was something. He might release it back into the wild—no... the squirrel shall stay with him for further study.
Might try breeding and see how that works.
Oh well, next test.
On a side note... the squirrel used Magnet Release...
HOUR TWO: BUNPUKU'S CELLS VS. SHUKAKU CHAKRA
Under the microscope, Bunpuku's blood cells pulsed erratically.
When Shukaku's chakra was introduced, the cells ballooned in size, the membranes destabilizing under pressure. More than half ruptured. The rest seemed to adapt—but sluggishly. Like the body had been forced to make peace with the beast over decades.
There was no harmony at all. The Bijū chakra just seemed to want to take control. He continued to study it under his microscope. Hm... he would need more advanced tech for this shit.
Well, maybe it was time... for Aizen Sōsuke to strike again. Hm. He would need to hunt someone with a bounty, kill them, and use that money to buy some quality material.
Maybe build himself a spy network.
Now for his third test.
He gazed at the differences in the cells. With Shukaku chakra mixed in, the Wind and Earth elements seemed to be blending very well, as if becoming the Jinchūriki of the One-Tail immediately gave someone Magnet Release.
It was either that, or repeated contact with Shukaku's chakra did that... or, since when Shukaku took over, his chakra basically flooded the user's system, the user's system learned to take a piece of that shit.
Think of like the Yuji, Sukuna situation.
Either way, this resulted in Magnet Release.
HOUR THREE: TSUNADE'S CELLS VS. SHUKAKU CHAKRA
Now this was different.
He introduced the same chakra to her cells and observed.
No rupture. No instability.
Instead, her cells flared with vitality—absorbing, adapting, and stabilizing the energy with shocking efficiency. Not only did her cells hold firm, but they began to pulse in rhythm with the chakra's fluctuations.
Stronger mitochondria activity. Accelerated regeneration potential. Chakra flow control even under foreign influence.
"...Senju DNA. Hah. That explains Hashirama," Seijuro muttered, scribbling down notes. "Natural compatibility with Bijū chakra... good to know."
Though, he did notice... some pushback, as if her cells weren't the best for this. Hm. Maybe she couldn't be the Nine-Tails' Jinchūriki.
Oh well.
Speaking of which...
He tested his own cells to observe mitosis—for research purposes.
Hm... okay. So, using that seal, although not to the same extent as Tsunade, he was now a bit older than he actually was.
Roughly a day or two older.
It was either the seal, or the Bijū chakra doing so much damage to his cells.
Hm. He needed a way to fix that.
Under the microscope, he began analyzing Nawaki's cells. Maybe he could find some shit there.
HOURS FOUR TO FIVE: PREPARATION FOR INFUSION
Now came the real work.
Seijuro drew a clean circle on the floor using ink made from crushed chakra-suppressing minerals. Inside the circle: a sealing matrix designed to regulate the flow of foreign chakra and prevent rejection.
He removed his shirt, exposing the intricate pattern of seal arrays on his torso—old, custom work layered like armor beneath the skin.
He took the seal with Shukaku's chakra on it and sighed a bit.
Before—without another thought—the very next second... he began sealing all of that chakra into himself.
The pain was... divine.
The chakra roared through his network like molten glass, screaming against his bones, threatening to tear his coils apart.
He gritted his teeth, forcing his chakra to sync with the incoming wave, letting the seal guide the fusion instead of brute-forcing it.
Every vein in his body lit up.
"Fuck, this shit hurts," he groaned... the seal on his stomach began to spin around. What seemed to be nine little stars appeared, imprinted into it.
Two of those stars seemed to be filled out.
"Two Bijū down... eight more to go," he said to himself.
He needed to test this new power of his.
...He would need a test drive for those new powers.