Walking through the bars of the cage, Mirai found himself in an even larger, more cavernous space. The darkness receded just enough to reveal the true form of the Nine-Tails—a massive, red-orange kitsune with black fur around its menacing red eyes that stretched up to its ears. Its nine long, swiping tails moved with a restless, ominous energy, each one crackling with latent power.
Scrutinizing the beast, he marveled at its sheer power compared to the other Tailed Beasts he had encountered in the war. Even with its chakra halved, the Nine-Tails's size and chakra were tremendous, a testament to its legendary and feared status.
Suddenly, Mirai leaped into the air, narrowly avoiding the massive, razor-sharp claws of the Nine-Tails. The fox's eyes gleamed with a ferocious, almost malicious satisfaction. Before Mirai could regain his balance, a flurry of the Nine-Tails's gigantic tails came crashing toward him with tremendous force.
In this subconscious plane, projecting his own chakra, means conveying his will and soul. So he can use use all his present abilities and items.
Reacting swiftly, Mirai summoned his unique ability, controlling the Mercury to form a medieval-style shield in front of him. The tails struck the shield with a resounding impact, sending vibrations through his entire body. Despite the shield's protection, the sheer power of the blow sent Mirai hurtling through the air.
He crashed down onto the flooded floor of the mindscape, the water splashing up around him as he skidded to a halt. but he quickly regained his footing, the liquid metal of his Mercury armor shimmering and reforming around him.
The Nine-Tails let out a roar that echoed through the cavernous space, its eyes burning with a mix of rage and amusement. "Do you see, human? Your efforts are futile against my power."
Mirai, undeterred, stood tall, his eyes locked onto the beast with a frown. As he took a scroll from his ninja pouch and unsealed it to reveal an already prepared large amount of Mercury, he spoke with a grim resolve. "One of my flaws, as Minato always criticized," he began, "is that I hold grudges. I'm not as forgiving as he was."
He revealed, "My purpose here isn't as pure as just helping Naruto. It's to unwind. Ever since I returned to Konoha, I've kept my rage bubbling inside me. Now, I have a suitable target capable of taking it."
The Nine-Tails's eyes narrowed, its voice dripping with disdain. "I already noticed it. You reek of negative emotions, but your hatred is still only a grain compared to mine. I am the incarnation and living embodiment of hatred."
Without further warning, the Nine-Tails began forming a [Tailed Beast Ball]. It swallowed the dense sphere of chakra, and moments later, a massive beam of destructive energy shot forth from its mouth, obliterating the area and churning the water into waves.
Mirai reacted swiftly, compressing and solidifying Mercury into a massive, smooth shield. The shield absorbed and redirected the beam upward, where it exploded violently against the roof of the cavernous mindscape. The force of the explosion sent rubble cascading down, but the remaining Mercury swiftly engulfed Mirai, forming a protective cocoon around him. While, the Nine-Tails's tails lashed out, pulverizing the falling debris with brute force.
Those tails lashed out next at Mirai with relentless fury and deadly accuracy, but he was ready. He moved fluidly, magnetizing his body to dart between the swiping tails with a blurred and controlled movement.
With a deft leap, Mirai stepped on one of the massive tails, using it as a springboard to propel himself higher into the air. As he soared, he quickly formed a series of hand seals. The Mercury responded to his command, shaping and hardening into multiple coin-like discs. A current of lightning chakra converged around his arms, charging the discs with immense power.
"[Railgun]" Mirai muttered, unleashing a barrage of electrified Mercury coins. The coins accelerated with incredible speed, raining down on the Nine-Tails like a storm of deadly projectiles.
The beast tried to shield itself with its tails, but the relentless assault was too much. The ground around the Nine-Tails shattered and scorched under the onslaught, the beast's fur singed and smoldering. Roaring in pain and rage, the fox unleashed a powerful force of pressure and destruction, a shockwave that deflected the next wave of attacks and obliterated the surrounding infrastructure.
Despite the destruction, the cage holding the Nine-Tails remained unaffected, its bars standing strong and unyielding.
The Nine-Tails's roar reverberated through the flooded mindscape, pushing Mirai hard against the wall, breaking it with a resounding crash. He fell back into the water, kneeling and taking a moment to catch his breath.
The Nine-Tails stood unsteadily right after, its scorched fur the only sign of the battle. It cursed, its voice a guttural snarl. "You bastard, do you think you can beat me?"
Mirai rose to his feet, his resolve unshaken. "I'll win!" He affirmed, glancing behind him to see Naruto standing far away on the other side of the cage, where the terrain remained untouched by their fierce battle.
Taking out four scrolls similar to the previous ones, he unsealed them, releasing another massive amount of Mercury in a cloud of smoke. The liquid metal danced around him, responding to his precise hand seals.
"[Mercury Golem]" Finished with putting together his technique, the Mercury surged forth like a tsunami, engulfing and merging into a colossal towering silver armored medieval knight. Each hand of the golem held a massive shield and sword.
The Nine-Tails, on its four limbs, froze momentarily at the sight of Mirai's avatar. Memories of battles long past flickered through its mind—Hashirama's [Wood Human] and Madara's [Susanoo]. These recollections sent the beast into a blind rage, and it charged, firing multiple uncompressed [Tailed Beast Ball].
Mirai, who was controlling his metallic avatar from behind the knight's helmet and its visor, had his hands and feet submerged in liquid metal for more meticulous control, controlled the golem to move with fluid precision, each motion an extension of his own. The silver knight stood tall, meeting the destructive orbs head-on with its shield. Each explosion pushed the knight back slightly, creating massive shockwaves and waves that reverberated through the mindscape.
Amidst the rising dust, the Nine-Tails charged on all fours, its massive form barreling toward Mirai with ferocious speed. Without hesitation, Mirai retaliated and directed the mercury knight to meet the beast head-on. The knight's massive sword clashed with the fox's hard tails, creating a typhoon of wind pressure that howled through the underground complex.
Mirai gritted his teeth, pushing the mercury knight forward with all his strength against the steel whips like tails of the fox. But he suddenly found himself halted and stranded, feeling an unexpected, familiar chakra. Before he could react, he was teleported a distance away from the raging beast. As he steadied himself, he noticed the Nine-Tails was forcibly put to sleep, its massive form lying still and its ferocious eyes closed.
Mirai then heard a familiar, gentle voice that provoked many of his emotions. "I sensed a disturbance in the seal, so I came to check. I didn't expect to find you battling the Nine-Tails, Mirai. Still as impulsive as ever, I see."