The Genjutsu Devil of Konoha

Time skip.

Seijuro was currently with his squad. His clone had gone to take a piss, and they had switched back then. He got what he wanted—currently, he didn't have the seal on him.

Why, you may ask?

Well, he had two Byakugan users in his squad and like six Sharingan users. He was not finna get caught lacking so close to his goals.

He had the chakra—it was sealed away somewhere near Takigakure.

Fugaku seemed to be quite thoughtful. No, poor Seijuro wasn't in any trouble. Seijuro had taken care of the Iwa-nin on his side, and his side had taken care of the Iwa-nin there. One of them might've escaped... but still.

Seijuro's team showed clear proof that they had, indeed, squad-wiped everyone, and since they had two Hyūga and a sensor in their squad, their claim couldn't be denied.

So if an Iwa-nin did manage to sneak in, it would be because of the Uchiha side... which, to be fair, would be a big deal—but considering the Konoha Elders, the backlash for this would be massive.

He already got the report from Takigakure... Iwa was here for the Hero Water.

Luckily, they were able to corner the guy, yet he drank the water and proceeded to beat the ever-loving dogshit out of them.

Before he could kill Fugaku, however, the side effect kicked in—and the man's hair turned white... he aged like 200 years in a second, withering away into ash and nothing more.

The side effect seemed... quite severe.

But the buff in power was no joke. Going from losing the 6 vs 1... to suddenly beating the breaks out of everyone and only losing because he monologued for too long.

Well, he had the report.

Time to report back to Konoha.

"We move at dawn," Fugaku would say, looking at his squad.

Everyone nodded. The order was loud and clear. They wasted too much time here already—so now it was time to skedaddle away.

Seijuro, meanwhile, seemed to be quite thoughtful, though he said nothing.

Fugaku could roughly guess what the boy was thinking.

Considering the tunnels they were making, the Land of Earth was not likely to give up on this. So they'd more than likely attempt something else.

Though that wasn't the boy's thought.

Seijuro was more worried about the seal currently not on his body.

Which, to be fair, Tsunade was aware of.

To her and the Hokage being the only people aware of the seal, it was meant to filter out his chakra. If another chakra tried to influence it, the filter's job was to remove it—alongside forcing his Id to never take control.

It was technically his seal to help take control of his body and force his Id back, so there shouldn't have been anything to worry about.

And thus, later that night, Seijuro left a shadow clone in his bed, while he himself went outside, a Genjutsu cast over him.

He arrived at his destination... entering the trunk of a tree, he released his Genjutsu—not the one on himself, but the one on the seal.

Upon seeing the seal, he smiled... time to become a pseudo-Jinchūriki.

He opened the scroll and removed his shirt so that he was shirtless. All the seals present on his body were now visible to the naked eye.

It was time to absorb some Bijū chakra.

And thus, he began using his seal.

Yūgō Fūin Jin

"Fusion Sealing Array"

(Also known as: The Quiet Beast Ritual or Chakra Osmosis Seal)

🔖 Classification:

Type: Custom Fuinjutsu (Forbidden-tier, Self-Created)

User: Seijuro Kurama (original inventor)

Function: Gradual fusion of Bijū chakra into the user's chakra system

Rank: S-Rank+

Danger Level: Highly restricted

⚙️ Concept & Purpose:

The Yūgō Fūin Jin was not made to control a Tailed Beast.

It was made to synchronize with one.

Instead of using the typical Uzumaki or Konoha sealing systems—designed to suppress, isolate, or violently weaponize Bijū chakra—Seijuro created this seal to act more like a chakra symbiote incubator.

It gently draws the Bijū's chakra into the user's own coils over weeks, months, even years, and rewrites the user's chakra nature to be more potent, more dense, and far more versatile.

💡 How It Works:

Multi-Layered Chakra Absorption Spiral

A complex spiral seal is etched into the user's abdomen or spine, broken into concentric conversion rings.

Each ring functions as a regulator, absorbing only a minute, safe amount of Bijū chakra daily.

Osmosis Conversion Protocol

The absorbed chakra is filtered through micro-seals that match and slowly align the Bijū chakra to the user's unique chakra signature.

Over time, this causes the user's base chakra to mutate, becoming:

Heavier

More responsive to nature transformation

More resistant to spiritual damage

Impressive in quantity

Seijuro began slowly absorbing Bijū chakra into his body, making sure to direct a vast majority of that chakra toward the seals.

As more and more Bijū chakra was absorbed into the boy's body... what seemed to be a Tailed Beast Cloak could be seen enveloping him.

And they whispered back.

Seijuro felt himself losing control over himself—he could feel the beast's will trying to overwrite who he was.

Thank god for those seals present—the seals that made sure his chakra leak couldn't be felt by the outside world.

He currently had four tails.

The power amp was insane—shit felt amazing. So good.

It was like a drug. He wanted more. He wanted so much more from this.

A dark chakra enveloped his body.

Bijū Chakra Mode... Second State.

...

Holy shit...

In this state... he had way more chakra than even 10 Tsunade.

Let's go—might be more than that, he doesn't know. His chakra amount was just increasing and increasing.

He needed to control himself.

"AHHHH!" As Seijuro was able to forcefully remove himself from this state, he groaned, his skin red... Bijū chakra was dangerous.

Poisonous, even.

Seijuro's body would eventually build up a resistance to it... but not now.

Now, it was weak against it.

It would get better...

He thinks.

A/N....1 down.....8 more to go.