Night never really came in the underground.
Not in the sanctuary beneath Uzushio.
The cavern pulsed with seal-light — soft glows of chakra-infused ink along the stone walls, coded in ancient Uzumaki script. It was a tomb, a library, and a forge all at once.
Naruto stood barefoot on the seal circle, breathing slowly. His skin glistened from training, not sweat. His body no longer fatigued from exhaustion — it had adapted.
Kurama stirred inside.
"It's almost complete."
Naruto didn't reply.
He looked down at his palm.
A sphere of chakra hovered — raw, unstable.
The early form of Rasengringu.
Three months he'd spent studying every property of the Rasengan. He'd broken it down into motion, torque, chakra density, chakra nature compatibility, and control layers. Then he broke it further.
The core remained — spiraling chakra compressed without shape.
But Naruto wanted more.
He wanted a technique that didn't just destroy.
He wanted one that erased.
So he rebuilt it — with rings.
Seven chakra rings. Each one tied to an element.
Wind spun the core.
Fire heated the outermost ring.
Lightning surged between them.
Earth grounded it.
Water compressed it further.
Yin and Yang formed a stabilizing shell.
It didn't spin.
It hovered, orbiting itself like a moon caught in its own gravity.
He called it Rasengringu.
The Spiral of Collapse.
The first time he released it, it cracked the bedrock for fifty meters in every direction.
The second time, he realized it could be weaponized in silence.
No hand signs. No flash. No surge.
Just pressure.
Unseen. Unheard.
Kurama saw it happen and fell silent for ten minutes.
"That thing," the fox finally whispered. "That's not a jutsu. That's chakra re-imagined."
Naruto nodded.
"It's just the beginning."
He began working on flight next.
Not the floating chakra techniques of Cloud shinobi.
Not gliding.
True flight.
He didn't copy anyone.
He studied chakra pressure zones beneath the feet.
He combined his sage control with gravitational disruption seals — forgotten theories buried in Uzumaki scrolls, originally meant for aerial surveillance anchors.
He made it better.
He fused wind chakra with magnetic counterforce, creating an equilibrium zone beneath each foot.
It took weeks.
Dozens of failures.
A fractured ankle.
But by the end of it—
He was standing in midair.
Silent.
Still.
Watching the world below him, no longer tied to its dirt.
Kurama laughed.
"Now you're cheating."
Naruto didn't.
Because this wasn't cheating.
This was war.
He perfected five more techniques.
Each one carved from necessity.
Higan no Tate — a flame barrier that inverted physical force and redirected it with equal momentum.
Kuro-Fuuka — Black Wind Clone. A clone made of wind and flame, that detonated with a vacuum effect on death.
Yoru Keiyaku — Night Contract. A sealing array that locked a user in place through chakra recognition — a trap jutsu disguised as a shadow.
Jougan Tenkai — Spiral Eye Unfolding. A visual seal that recorded movement like a camera, then could replay it in real-time to adjust his reflex timing mid-battle.
And the final one…
He called it Tsumi Sajin — Sin Dust.
A micro-particle chakra field that shredded chakra signatures from a wide radius, rendering even sensory shinobi blind.
Kurama warned him, "This isn't a shinobi art anymore."
Naruto responded: "It's survival."
Along the cavern walls were scrolls labeled by village: Cloud, Stone, Mist, Sand, Leaf.
From each, he had drawn something.
A technique.
A formula.
A lesson in how the world fought.
He didn't use them.
He rewrote them.
He wasn't just building strength.
He was building an ideology.
One where peace wasn't asked for — it was engineered.
And for that, the world would have to bleed.
By the end of the second year, Naruto stood before a new seal.
The one that would store his most volatile creations — a vault of chakra constructs and incomplete jutsu meant only for war.
He didn't fear losing control anymore.
Because he understood something they had all missed:
Fear wasn't weakness.
It was raw power with no leash.
And he had built the leash himself.