As the last trace of color vanished from his left eye, the black flames of destruction began to blaze and spread across the endless Sea of the Underworld.
Even the Sea of the Underworld, capable of cleansing and corroding everything, could not resist the advance of Amaterasu's black flames.
Amaterasu could unleash black flames over a vast area, burning its target completely, and the flames would persist, spreading until the target was utterly consumed.
Although in the original story it never killed anyone, its overwhelming power was undeniable.
Yuki Seisui's target was this entire Sea of the Underworld.
The Sea of the Underworld would persist until the black flames had finished burning it completely.
Ordinary objects or ninja would be incinerated in moments by the black flames, but the Sea of the Underworld was different. Being a Mangekyo Sharingan ability itself, it existed on a similar tier of power as Amaterasu in certain respects.
The black flames consumed the waters, transforming them into rising mist.
Previously, in Uchiha Haru's experiments, the corrosive properties of the waters had already been tested.
No matter what form it took, the waters retained their corrosive nature.
Amaterasu spread endlessly across the Sea of the Underworld, sending countless steam plumes into the sky.
Konan, hovering in midair, watched Seisui unleash the black flames across the ocean. Alarm bells rang in her mind—she tried to evade—but the flames spread far too fast.
Her speed felt almost stagnant against the advancing black flames. What was in her sight had not yet been completely engulfed, but in mere moments, the arena's infinite space began to heat up, and the steam crept ever closer.
Seisui rode the waves, propelling himself forward with the Sea of the Underworld beneath him.
Though he controlled both the Sea of the Underworld and the Amaterasu flames, he was not invulnerable.
Fortunately, even with his left eye fully blind, his control over the Sea of the Underworld remained absolute.
The flames spread quickly, but he moved faster still.
As he fled, pained screams reached him from the distance.
Seisui didn't look back—three shadow clones had already vanished when touched by the rising mist.
Konan's cries could only mean that the corrosive steam from the blackened waters had begun to eat away at her.
Though the Sea of the Underworld burned and evaporated, the total substance remained. The water dispersed, forming another state: the Yomi mist.
The mist retained the same corrosive properties as the Sea of the Underworld, even more insidious and hidden.
Seisui continued to flee.
Minato, observing from a god's-eye view, winced at the sight of Konan's legs being corroded away, bone and all.
After all, she was their shared junior—a student of Jiraiya-sensei and the only female among his students.
Uchiha Haru had been excluded. Though Jiraiya treated all equally, Haru was never truly his student.
The true students numbered five: Minato, Seisui, Konan, Nagato, and Yahiko.
"Poor girl," Minato muttered, his spirit unable to bear watching.
He appeared behind Seisui, leveraging his god-like perspective.
Konan climbed higher, evading the corrosive mist, while Seisui, sensing the roaring wind around the waves, muttered to himself:
"Did I… go a bit too far?"
The projection of Minato nodded beside him.
Seisui couldn't see or hear Minato, but he knew his friend would always be near. And Minato knew the remark was for him.
Perhaps that was the silent understanding shared between men.
=======
Meanwhile, Konan had ceased struggling.
The arena offered no resistance, no boundaries—just an infinite vertical void.
She glanced at her dwindling chakra and at the mist below, bitterly twitching her lips. Her pure white wings fell away as shredded paper.
She herself became a free-falling body.
The corrosive Yomi mist showed no mercy.
The instant she touched it, her legs were gone, leaving only white bones. A second later, the bones too disintegrated under the corrosive power.
"It's over," Seisui murmured.
Sensing the arena's space beginning to dissolve, he understood—Konan was gone.
He did not speak further.
As the arena faded, the conjured Sea of the Underworld returned to its original dimension.
It hadn't come back empty-handed—the black flames of Amaterasu burned along with it.
In a void, countless spheres floated. One of the mid-sized alternate dimensions trembled suddenly.
This was a world enveloped entirely by waters. Only this water existed; the entire realm was a vast Sea of the Underworld.
The conjured Sea of the Underworld appeared above this space, descending with the black flames of Amaterasu.
To Seisui, Minato, and Konan, the infinite Sea of the Underworld seemed immeasurable. In this space, it was a mere droplet.
Falling into the real Sea of the Underworld, it was like a grain of sand plummeting into a desert.
No waves stirred.
Yet even such a seemingly insignificant "grain of sand" carried Amaterasu flames.
Seisui's aim was absolute: to incinerate the Sea of the Underworld completely. Amaterasu would see to it.
As the airborne "Sea of the Underworld" fell, the flames spread even faster, engulfing the unconjured waters.
The water vapor, formed from evaporation, rose, condensed, and fell as rain, cycling endlessly under the black flames.
Seisui did not know the details.
As Konan perished, Seisui regained full awareness. His previously blind left eye restored to normal.
Konan, revived by the arena's rules, bounced slightly, heart still racing, glancing at her pale legs.
They had just been gone.
Though aware of the arena's rules, every resurrection felt dreamlike, surreal.
Life and death interwoven in fleeting moments left her strangely exhilarated.
A smile graced her face. Each "death" brought new insights, new sensations of life.