Just as Son Goku completed the second fusion, the rest of his shadow clones popped out of existence in puffs of smoke.
The suddenness of it took him by surprise. He immediately attempted the Kage Bunshin no Jutsu again, but each new clone materialized only for an instant before similarly dissipating.
After Goku dispelled his fused state, he could create shadow clones normally again. But the moment he re-entered the twice-fused form, the technique failed. After several attempts, he pieced together the reason.
A shadow clone shares an intrinsic, mystical link with its creator.
All sensory input and physical strain experienced by a clone are transmitted back to the user upon its dispersal.
For instance, sending multiple clones to train to exhaustion could overwhelm the original body with debilitating fatigue when they vanished.
The reverse principle also applied. Goku's double-fused state pushed his power far beyond his normal limits.
Through that profound connection, that overwhelming energy also affected the structural integrity of any other shadow clones he tried to create.
While his main body could withstand the strain, the clones could not, becoming instantly unstable. In this heightened state, maintaining additional clones was impossible.
Though it was a minor limitation, Goku was far from disappointed.
The power he now commanded made him a formidable force even among peers of similar standing. Should he ever face a superior foe, he possessed a decisive trump card. In the perilous world of Dragon Ball, this was a crucial new layer of security.
Returning to Naruto's apartment, he found the women still deeply engrossed in their chakra refinement.
Not wishing to disturb them, he turned his own focus to studying the two forbidden jutsu he had memorized: the Kekkei Kakusei no Jutsu and the Kimera no Jutsu.
---
The next morning, Naruto had already left early for the Academy. After breakfast, Goku led the group to the Hokage's office. While the women were all quick studies, self-directed learning in ninjutsu would only take them so far.
They needed a proper instructor, and the Sandaime Hokage was the most suitable candidate available.
"You want me to teach them?" Hiruzen looked at Goku in surprise, then gave a weary smile. "With a husband as formidable as you, do they truly require my instruction? Besides, in the wake of yesterday's… Uchiha incident, my time is scarcely my own."
"My expertise lies in taijutsu and raw power, not the finer points of ninjutsu theory. That's where I need your help," Goku stated plainly. "And I won't ask for it for free. Consider it a favor owed. If you ever face a genuine crisis, I'll lend my strength once."
Hiruzen's eyes sharpened immediately. A single favor from a being of this caliber was akin to a priceless safeguard. How could he refuse? "In that case, I will make the necessary arrangements to instruct them. You have my word."
And so, the women began their formal ninjutsu training under the Sandaime's tutelage.
Goku sat in for a short while, but finding the pace too slow, he created a single shadow clone to remain with them—serving as both a protector and a student, killing two birds with one stone.
The real Goku then slipped away to wander the streets of Konoha.
The village was abuzz.
"Have you heard? The entire Uchiha clan… apparently wiped out by one of their own, Uchiha Itachi…"
"Impossible! That's Konoha's strongest clan! How could one man… and we're only learning of it now?"
"It's true. I passed their compound this morning—the whole place is sealed off by ANBU."
"Uchiha Itachi… that genius on par with Shisui?"
"That's the one. I heard he's already been branded an S-rank missing-nin…"
Whispers and shocked exclamations followed Goku wherever he went. So, the news has broken.
Konoha won't be quiet for a while, he mused with a faint smile, paying the gossip little mind. He made his way to the secluded training grounds in the Konoha hinterlands and entered his World Ring.
Inside, he created not dozens, but tens of thousands of shadow clones. Their collective task: to deconstruct, analyze, and master the two forbidden jutsu.
As the saying goes, many hands make light work. In a little over ten minutes, the research was complete.
The combined intellect of thousands of Gokus had not only fully mastered the techniques but successfully synthesized them into a new, refined form of ninjutsu.
Satisfied, he dispelled the clones and took out the pair of eyes he had retrieved from Uchiha Fugaku. "I never planned on swapping my own eyes, but that Rinne Tensei technique… that's something I need." His expression was resolute.
Without fanfare or hesitation, he raised his right hand, fingers like claws, and with brutal efficiency, gouged out his own right eye.
Blood welled, but Goku didn't so much as grunt. He swiftly inserted one of the Sharingan into the vacant socket.
The moment the foreign orb was placed, the blood vessels in Goku's socket writhed and connected with startling speed.
In mere seconds, his right eye had settled, vision restored. With his nigh-immortal, regenerative constitution, regrowing a lost limb was trivial; integrating a new eye was effortless.
He repeated the process with his left eye.
With a thought, his eyes blazed crimson. Three tomoe slowly spun into view—the perfected Three-Tomoe Sharingan of Uchiha Fugaku.
Goku looked around. The flutter of a distant bird's wing appeared as a languid, detailed dance. "The dynamic visual tracking is impressive," he noted with a satisfied nod. Then, he began channeling his own monstrous, ocean-like spiritual energy into the transplanted doujutsu…
The three tomoe began to spin rapidly. What were genetic curses or evolutionary rules in the face of such absolute, overwhelming power?
Under the torrent of Goku's spiritual force, all limitations were rendered meaningless. The tomoe morphed, merging into a complex six-pointed star pattern… which then rippled and warped, forming concentric, wave-like circles in both irises…
The sclera flushed red once more, and at the very center of the rippling pattern, a stark black six-pointed star materialized. The transformation stabilized in this final, majestic form.
Goku took out a small hand mirror—who knew which of the women it belonged to—wiped the traces of blood from the corners of his eyes, and examined his reflection.
The eyes staring back were a breathtaking fusion of Mangekyō intricacy and Rinnegan grandeur. A smile spread across his face.
"They say the Rinnegan is the Sharingan's final evolution… but it seems mine has evolved one step beyond even that. A most welcome surprise."
"Now… let's test their power."
He exited the World Ring and used Instant Transmission to arrive at a desolate, mountainous region far from any settlement. Gazing at a distant peak, he murmured, "Amaterasu."
Whoosh!
Black flames, darker than the void between stars, erupted and enveloped the entire mountain. In the span of a breath, the several-hundred-meter peak was utterly consumed, reduced to nothing.
Yet the flames did not die; they raged on, burning relentlessly into the earth, swiftly carving out a crater hundreds of meters wide and dozens deep.
Left unchecked, they gave the terrifying impression they might burn through the world itself.
The Amaterasu unleashed by Son Goku and the one used by Itachi existed on different planes of reality—there was simply no comparison. The strength of the user defines the strength of the technique: an immutable law.
"A fine pair of eyes indeed," Goku said, his voice low with approval. A strange ripple emanated from his left eye, and the all-consuming black flames vanished as mysteriously as they had appeared.
"In this form… I shall call you Shingan. The Eyes of God."