Reborn in Jujutsu Kaisen as a Zenin

Twenty-five years of patient infiltration culminated in this moment. The assassin moved with practiced silence through the Zenin compound, his cursed energy perfectly suppressed after decades of refinement.

His position as a servant had finally granted him access to this most crucial target – the boy who had humiliated the Gojo clan's heir.

Indra's quarters stood unguarded, just as expected. The boy's arrogance in refusing protection would be his undoing. Or so the assassin thought.

Moonlight filtered through paper screens, illuminating Indra's sleeping form. The child lay perfectly still, his breathing deep and regular.

The assassin's cursed technique manifested – a blade of pure energy designed to bypass standard defenses.

He struck.

The blade never reached its target. Instead, it met an invisible barrier of crimson energy that the assassin's decades of experience hadn't detected.

There was no resistance, no clash of techniques. The aura simply... unmade him.

Indra didn't even stir as the assassin's body burst apart, painting his quarters with gore. His Gentle Death technique had protected him automatically, without conscious thought.

In the morning, servants would find only bloodstains and fragments.

A message written in the clearest possible terms: guards weren't refused out of arrogance, but because they were unnecessary.

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Indra opened his eyes to the familiar sight of bloodstained walls. The morning sun cast interesting patterns through the red splatter, a sight that had greeted him four times now since his victory over Satoru.

He rose unhurriedly, noting how his cursed energy had maintained decent efficiency through the night.

The Reaper's Cloak, as others had begun calling it, had performed exactly as intended – maintaining just its lethal properties while sleeping, two other attributes temporarily suspended to conserve energy.

"The Gojo clan grows predictable," he mused, stepping carefully around the mess. Their attempt wasn't meant to succeed – merely to gather data.

How does his defense function during sleep? Can it be overwhelmed? Does it require conscious control?

Questions now answered at the cost of another expendable piece. Though this one had been cleverer than most, managing to maintain his cover for twenty-five years. Almost impressive.

A servant's startled gasp at his door drew his attention. "Young master! The blood-"

"Have it cleaned," he interrupted calmly. "And inform my father that the Gojo clan's latest inquiry has been... addressed."

The news spread through the compound usual speed. Another assassination attempt, another failure - as to be expected.

In his study, Naobito received the report with a sharp smile. The Gojo clan's attempts to understand his son's technique were becoming almost routine.

Each failure adding to the Zenin clan's prestige, each dead assassin a testament to their heir's power.

Kisara, arriving for her morning training, noted the servants' hurried cleaning of Indra's quarters without comment.

This dance had become familiar – the Gojo clan's probing, Indra's effortless defense, the political messages encoded in each failed attempt.

"They're growing desperate," she observed as they began their practice. "Four attempts in such a short time suggests they're struggling to understand your technique."

"Let them waste resources," Indra replied, supervising her Divine Dogs manifestation. "Each failure only has them lose valuable information gatherers hidden within the shadows of the clan."

"Though I wonder," Kisara continued, "if these attempts are sanctioned by the clan head himself. They don't fit his... image."

Indra watched her progress with his usual focus. "Haruto Gojo is many things, but he's not foolish enough to waste decades-placed spies on information gathering that the Six Eyes couldn't achieve."

"Then who-"

"Is it not obvious? The clan elders, of course. Old coots who always need to have things their way." Indra stated. "Their pride demanding answers, even if their heir and clan head seem to have accepted the outcome."

"Your Divine Dogs' manifestation has stabilized," Indra observed, watching the shikigami move with fluid precision.

"And Jade Frog's tracking abilities are nearly perfected. It's time to attempt something more challenging."

Kisara's eyes widened slightly. "Nue?"

"Yes. Your cursed energy control has developed sufficiently these past years. The aerial combat capabilities Nue offers would significantly expand your options." He paused, studying her reaction.

"As always, if the ritual becomes too dangerous, I'll terminate it immediately."

Indra's technique as is to be expected could simply dissolve the shadow before it could harm her – a safety net that had allowed her to develop her technique without the usual risks Ten Shadows users faced.

"The previous users' notes suggest Nue is particularly aggressive during the taming ritual," Kisara noted, already preparing her cursed energy. "Its lightning attribute makes it especially dangerous."

"Begin when ready," Indra replied without concern.

"Before we begin," Kisara said, considering the open training ground, "wouldn't it be wiser to conduct the ritual in an enclosed space?

Nue's lightning abilities could draw unwanted attention and it would be easier for me if the shadow couldn't make use of its flight."

"A practical idea," Indra agreed. "There's a suitable cave system nearby. The stone walls will contain both the visual and auditory elements of the ritual."

They made their way to the cave entrance – a natural formation that the Zenin clan had long used for various training purposes.

Its depths would provide both privacy and containment needed.

The cave's darkness deepened as Kisara began the ritual, her cursed energy drawing shadows toward a central point. 

First came the static – tiny electrical charges that made the air itself feel alive. Then the low rumble of contained thunder, echoing off cave walls.

Nue's manifestation began with a crack of lightning that illuminated every crevice of the cave.

Unlike in open air, its electrical display had nowhere to dissipate, creating a web of purple-white energy that danced across the stone surfaces.

The shikigami took form – more compact than its open-air manifestation would be, but no less deadly. 

Nue's first lightning strike hit empty stone as Kisara moved with efficiency. Divine Dogs manifested instantly, their forms flowing from the shadows to flank the chimeric beast.

In the confined space, Nue's massive form worked against it – each movement restricted by low ceiling and close walls.

The cursed tool sword Indra drawn as she charged and coordinated with her dogs. 

Divine Dogs herded Nue into an even tighter corner, their synchronized attacks leaving the lightning beast no room to maneuver.

A flash of what seemed almost like confusion crossed Nue's features – its natural combat style, designed for open aerial combat, rendered nearly useless in these stone confines.

Kisara pressed her advantage, sword and shikigami working in concert to further restrict Nue's movement until the powerful beast found itself completely immobilized.

Kisara struck quickly with her sword, taking advantage of Nue's trapped position. The blade cut clean through its neck.

As Nue died, its power flowed into her Ten Shadows technique, completing the taming ritual.

Now she could summon Nue whenever needed, the once-wild shikigami bound to her will through combat and death.

Watching this, Indra considered Mahoraga. The Mighty General of the Ten Shadows. The killing of the Shikagami is... not easy.

There is the theoretical possibility of having Piercing Ox - once tamed to build up enough power to kill him, but that was not guarenteed.

Since the time necessary for that build up requires constant maintenance of its manifestation which he doubts Kisara is able to do with her control and cursed energy reserves, high as they may be.

Yet, Kisara needs him to be truly someone worth noting. The rest of the Shadows though powerful and versatile would have her have a more supportive position rather a destructive force on the battlefield which he desires.

That leaves one option - he needs to alter the laws of the domination ritual to include himself as a cursed tool. 

It will not be simple. It is one of the techniques smiled upon by Heaven, just like the Limitless. And this time he would alter it far more fundementally than he did infinity, so the cost would most definitely be extensive.

He needs to consider this. What kind of Binding Vow would be viable without weakening himself.

"Good work," Indra stated simply, watching as Kisara tested her connection with Nue. "The confined space strategy proved effective. Remember it for future taming rituals."

Kisara nodded, her cursed energy steadily maintaining control over her new shikigami. Three powerful shadows now – each tamed through increasingly efficient methods.

Her growth was proceeding exactly as planned.

"We'll begin incorporating Nue into your regular training tomorrow," Indra continued.

"For now, focus on establishing a stable connection. Understand its capabilities fully before attempting complex techniques."

Finishing his words, Indra turned to leave. Time was a resource he couldn't waste, not with what was coming.

The Mad Brain - Kenjaku would not rest until Sukuna returned. The King of Curses, the first Son of Heaven, whose birth a thousand years ago marked the beginning of this era.

Satoru Gojo, the second, blessed with Heaven's own sight and absolute defense. And now himself, the third – the one who sets his path to determine how this millennium's story would end.

Three Sons of Heaven, Three Brothers in the sight of the above, each marking a crucial point in jujutsu history.

The Destroyer who began it all, the Observer who is supposed to see all, and the Conqueror who wills to shape its conclusion.

The Conquerer of the Millennium's End.

That is who he will be.

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(Author note: Hello everyone! I hope you all enjoyed the chapter!

Yeah, I'm basically gonna go with this concept of "Sons of Heaven."

I find it fitting with the whole "Honoured One" narrative.

They of course aren't literally sons of Heaven, but its just that they are at birth above just so many people, its like - I don't even know how to properly describe it.

I personally consider this whole thing from Sukuna to his death, a single Era, one ruled by the presence of the Evil King.

Since still Sukuna just by existing, drives Uraume to prepare for his return, Kenjaku to plan to bring him back so that he can be the central point till the Merger happens.

So yeah, I hope you all enjoyed it, and I hope to see you all later,

Bye!)