Naruto and his clones each took a separate passageway leading away from the main cavern. The tunnels were man-made and lit by fluorescent lighting; they interconnected in a seemingly random pattern that reminded Naruto of the second test in the Chūnin exam. His search was systematic. As he picked off any stragglers who had not been in the main cavern, he mentally crossed out the passageways he had already checked.
This room was empty. This tunnel was a dead-end. This room was also empty. And here was a dead-end. And another.
Naruto could feel his heart growing heavier and his focus giving way to a darker, lurking emotion. He was starting to wonder how high the tunnels ran, when with a jolt, one of his shadow clone's memories flooded his mind: Someone had sneaked up on it. It continued as one after the other, his clones were taken out. Right before his his last clone disappeared, Naruto saw in its memories a blur of movement—and then he was standing alone in the tunnel.
He heard it before he saw it: The subtle, almost indiscernible whistling of metal flying through air. Spinning around, Naruto brought up his tantō just in time to knock away what looked like several long needles—senbon. They were followed by a kick that spiraled down at him, which he blocked with his forearm before thrusting his tantō forward. His assailant leaned back, allowing the blade to swing harmlessly above his chest. Then, using Naruto's arm as a springboard, he flipped backwards through the air.
Taking in the ninja before him, Naruto realized two things in quick succession. One was that he wore the typical white mask of a hunter-nin from the Hidden Mist. The second was his right hand, which was swollen and grey in color: It was poisoned. In a flash, he saw in his mind's eye one of Mayu's poisonous birds swooping down and pecking at a dark figure.
He had been mentally preparing himself for a fight with one of the three S-ranked missing-nin. He knew nothing about this ninja, or about what kind of circumstances had brought a Kiri hunter-nin all the way to Gatō's hideout.
None of that mattered.
Sending a stream of wind chakra down his blade, Naruto struck.
...
As the chief toad of Mount Myōboku, while Gamabunta's giant size could dwarf even mountains, it had no bearing on his speed. With Jiraiya perched on his head, the chief's long tongue lashed out at a punishing pace, causing the earth to quake with every blow.
Their opponent, however, was a freak even by Akatsuki's standards. Gamabunta's initial attack had ripped the man's body apart in two, only for the two halves to re-join themselves using the same thick tendrils that had connected his arm to his body. Now, Kakuzu's entire body had darkened in color, and Gamabunta's attacks were no longer having as much of an effect.
Evading another blow that sent tremors through the ground, Kakuzu suddenly threw himself into the air. Black tendrils from his arms bulleted straight towards Jiraiya, and before he could react, the threads wrapped themselves around his feet. The surface below him gave way, and he was hurled off the chief toad's head. Wasting no time, Kakuzu arched back and unleashed a massive blast of searing fire in his direction.
Jiraiya didn't have to look back to know that the others, along with Hidan, were fighting behind him; if he didn't block the fireball, it was powerful enough to consume them all. It seemed that Kakuzu felt little sense of camaraderie for his fellow partner.
"Bunta!"
In response to his cry, Gamabunta's body swelled up. Just as the toad expelled a torrent of water towards the fireball, Jiraiya blew out: "Fūton: Gufū (Wind Release: Twister)!"
A tornado twisted around the torrent, producing a cyclone that collided into the fireball. Even then, it wasn't strong enough to dispel it, splitting it instead into two walls of fire that veered off in different directions—one disappeared into the fog of the marshlands, and the other slammed into the mountainside.
"Kakuzu, you bastard!" He heard Hidan howl. "You almost hit me!"
...
A deadly rain of icicles slammed into the ground where Naruto had been standing a split second before. As the fluorescent lights flickered above them, dust rained down from the ceiling and spidery cracks appeared in the tunnel walls.
The hunter-nin was as small in stature as Naruto, and he had a suspicion that their ages weren't too far apart. However, he had never before met someone his age who could keep up with him in speed—let alone push him to this extent. Moreover, even though the hunter-nin only had the use of his left hand, this did not seem to deter from his ability to perform seals in the slightest.
Nonetheless, judging from the sounds of battle coming from outside, Naruto did not have much more time to waste. He had to finish this quickly, before anyone else got hurt.
The two exchanged several more blows, neither giving way—when Naruto's tantō glanced against the swollen hand of the hunter-nin, who visibly jerked in pain. Seizing the chance, he directed a roundhouse kick at the other male which made contact, the impact sending his body spinning through the air. Electricity surged painfully about his feet, and Naruto and three of his shadow clones shot forward, a tantō raised in each hand, ready to impale the hunter-nin in from all directions –
And then all of a sudden, coming in through the far end of the tunnel, a seething column of fire spiraled towards them, consuming everything in its path.
There wasn't enough time. Naruto's momentum was carrying him forward, straight into the path of the fire. Did he know any jutsu that was powerful enough to counter it? Already, he could hear the roar and feel the heat on his face, but frantically, his mind raced through a dozen different things he could do –
"Hyōton: Hyōgan Dōmu (Ice Release: Ice Rock Dome)!"
The air around Naruto crackled, and everything around him was consumed in fire.
...
Things were not looking good.
Shirakumo was already dead; he had succumbed to a bizarre jutsu that connected Hidan's body to his. The jōnin's body lay crumpled on the ground, blood still seeping from the hole in his chest.
Panting, Rai flipped back and warily regarded the missing-nin, who currently wore an expression of utter ecstasy. He had known it, but Hidan was strong. Overwhelmingly strong. He had grown stronger since their time in Yugakure.
Even Sai seemed to understand the trouble they were in; he hadn't cracked a single insult since the battle had begun.
"Isn't it about time you made yourself useful?" Sai panted.
Well, it'd been a good run.
"I don't see you doing anything either," Rai snapped back.
Hidan kissed an amulet that hung around his neck and his black and white skin returned to its original color. Rai shot a look back up at Gatō's hideout, but it was quiet. He had to assume Naruto was still searching for Mayu and Tazuna. In the meantime, it was their job to keep Hidan busy.
Ink birds began to dive in Kamikaze-style, exploding around Hidan. Rai drew his kunai blades from his back, the chains connecting the dual blades clanking dully.
That day in Yugakure, Rai had been knocked out before he could do anything. Naruto had gotten most of the glory then, as he usually did, and Rai had sworn to himself that he would get his revenge.
Hidan had grown stronger, but he hadn't spent the past few years idly either.
...
The fireball that had consumed the tunnel sputtered away into nothing, and Naruto stared up at the dome of ice that protected both him and the hunter-nin. If he wasn't mistaken, it had just saved his life. But why?
As he watched, the dome disappeared, and Naruto lowered his gaze. The hunter-nin, panting in exertion, stood well within his reach.
The fireball had been the final blow; the tunnel ceiling had collapsed in, and amidst the rubble, they now stood exposed to the outside air. The sun had set while he was inside the hideout, and he found himself awash in the glow of moonlight. The shouts of battle echoed in the distance; the earth rumbled from the movements of Jiraiya's toad summon.
For the first time, the hunter-nin spoke. "The girl...was she one of yours?" His voice was higher than Naruto had expected.
"She did that to your hand." It wasn't a question.
"…Yes."
"Where is she?"
The hunter-nin didn't respond, and in his silence, Naruto knew. In that moment, as though he had been doused in ice cold water, everything became clear.
Powering his feet with chakra, he thrust his tantō forward. The hunter-nin jerked back in surprise—a fraction too late. The blade cleaved straight through his swollen arm. Yellow pus and dark blood burst out as the severed limb fell away, splattering Naruto's face. Staggering back, the hunter-nin let out a piercing scream and as though heeding his call, a blast of icy air began emanating from his body. His scream morphed into the sound of crackling frost, and before he knew it, Naruto found himself trapped in another dome. This time, it was made out of mirrored ice.
The sky grew thick with grey clouds and the moonlight faded. It began to snow.