Dust sifted from the tunnel ceiling, lanterns swaying on their hooks.
Then the outer alarm tags flared red.
"They're finally here," one of the sensory-nin muttered, voice tight.
Orochimaru was already standing in the central cavern, pale face tilted, golden eyes half-lidded. He didn't need to ask where.
The entire Den could feel it. The air shook like a drumbeat.
Outside, the night split. Kumo's strike force poured through the valley, their formation tight, precise.
At the front marched the Third Raikage himself, cloak snapping around his massive frame, lightning dancing faintly across his shoulders.
His two sons flanked him, A with his body taut and furious like a drawn bow, B with blades on his back and Gyūki's chakra already pulsing faintly in rhythm with his steps.
Behind them, three hundred hardened shinobi advanced as one.
The Den's outer watch-posts lit up in flame and chakra bursts. Kumo smashed them flat in minutes.
Inside, Orochimaru turned to the nearest communication-nin. "Pull the forward squads back into the first chambers. Don't waste them in the open. Mm… let the Raikage come to me."
Orders rippled through the tunnels.
More than two hundred inside were already moving, sealing formations snapping into place, kunai and scrolls pulled from belts.
These weren't ordinary defenders.
Every one of them was handpicked, veterans of six months of brutal attrition, hardened high-chūnin, jōnin, and elite jōnin, included in the greatest concentrations than everywhere else, purposely by Orochimaru. Root among them.
Ryusei felt the surge of enemy chakra as the first shock hit the outer barrier seals.
It was like a wall of thunder pressing down on the Den.
He grinned anyway, narrow eyes slitting further. "So it finally starts."
A louder tremor shook the cavern as the first sealing array shattered.
The light from outside spilled down the tunnel. Kumo had breached the outer layer.
Tsunade stepped up beside Orochimaru, arms crossed, expression grim. "They're not probing this time."
"No," Orochimaru murmured, a faint smile tugging at his lips. "This is the march."
Another crash echoed, closer now. Screams and steel rang down the stone halls.
The Den was about to become a battlefield.
The tunnels shook like a living thing.
Each impact from outside drove cracks down the stone, splintering seals in flashes of light.
Shouts carried in, broken by the roar of exploding tags and the crash of collapsing supports.
Inside the Den, Orochimaru stood at the center of the war cavern, hands folded inside his sleeves.
His golden eyes gleamed faintly, reflecting the torchlight as if he were studying insects through glass.
Around him, squads scrambled into formation.
Root operatives moved in silence, faces blank, while strike-nin laid tags across the walls, weaving seals into choke points.
The ground heaved again.
A line of defenders at the outer tunnel collapsed backward, bodies skidding across the stone floor. Lightning flared in the breach, blinding, followed by the deep boom of a voice.
"Out of the way."
The Third Raikage stepped through smoke and rubble, towering, his body sheathed in light.
Sparks crawled across his arms and shoulders like restless serpents.
His presence alone pressed down on the cavern like a stormcloud.
Behind him, A surged forward, fists crackling, eyes locked on the first target he saw.
B followed with a grin, blades rattling at his back, Gyūki's chakra licking faintly at the edges of his skin.
Behind the three of them, rows of Kumo shinobi pushed into the broken tunnel mouth, their formation tight, killing intent thick in the air.
For a heartbeat, the cavern held still. The Den's defenders tensed. The invaders stared in.
Then Orochimaru moved.
He stepped forward, smooth, almost casual, pale face framed by the fall of his dark hair.
His smile was soft, wrong, his voice calm as if none of the destruction mattered.
"So… you've come here yourself. Raikage-dono."
The Third Raikage's eyes narrowed, the glow of his armor flaring hotter. "You've hidden long enough, snake. Tonight, you don't leave this place."
Orochimaru's smile deepened. "Mm… let us see."
The clash came instantly.
The Raikage surged, lightning flaring brighter, stone fracturing under his feet as he lunged.
Orochimaru's body twisted, retreating just enough, hands already weaving seals as serpents spilled from his sleeves, hissing across the ground.
The cavern erupted.
At the same time, A broke left, slamming into the flank with speed like a thunderbolt.
Defenders flew back, scattered by his raw force.
B swung opposite, blades flashing, a wild rhythm in his steps as he cut into the wall of Konoha jōnin blocking his path.
The two sons carved twin paths through the chamber, straight toward the Den's heart.
That was when Tsunade stepped in.
She came from the side tunnel in a blur, green chakra already pooling around her fists.
Her voice cut sharply through the chaos. "Not one step further."
A snarled and launched straight at her, his fist meeting hers in an impact that split the air like thunder.
The shockwave ripped across the cavern, sending dust and shards raining down.
Killer B laughed, blades sliding into his hands as he circled her flank.
Ryusei was already moving.
He threw himself into the smaller tunnel beside Tsunade, his clones flashing into existence.
They intercepted Kumo squads trying to pour around her, cutting them off before they could swamp her duel.
His chakra burned in his veins, but his grin stayed sharp.
"So this is it," he muttered. "Let's see who cracks first."
The Den had become a battlefield, split into zones.
At the center, Orochimaru and the Third Raikage locked the cavern in a duel of monsters.
To the left, Tsunade clashed with A, her fists lit with healing chakra against his lightning armor.
To the right, B's blades spun like a storm, only Tsunade's reflexes keeping her from being overwhelmed, while Ryusei and his clones cut down the reinforcements that tried to tip the fight.
The decisive battle for the northeast front had begun.
Ryusei quickly realized through his sensing that the enemy was numerous and carried heavier firepower, as they had predicted.
So much so that Orochimaru's seals, traps, and tricks, thanks to terrain advantage and familiarity, would bleed them, but they wouldn't be enough alone.
If Konoha wanted to hold, someone had to tip the balance.
So Ryusei moved. He spread his clones into the chaos, masked and silent, slipping through smoke and broken stone.
His world-class sensing let him map the battlefield instantly, picking out captains, jōnin, and key squads holding the Kumo assault together.
His clones hunted them in pairs, striking fast, vanishing just as quickly.
Confusion spread in the enemy ranks, rippling outward.
But Ryusei was careful. He made sure that, at critical moments, his face was seen by Konoha shinobi.
They needed to know who was disrupting the enemy and saving them so majestically.
Orochimaru had already been generous enough to introduce him earlier to middle-ranks as the main supporting piece with a special mission during this defense, and his right hand for all of this, and Ryusei wasn't about to waste the chance.
Reputation was nearly as important as survival at this time.
He went further, channeling his recently mastered telepathic sensing into Konoha's own formation.
Warnings, position updates, orders, suddenly, squads that had been breaking were moving like a single body again.
Ryusei wasn't just fighting.
He was making everyone fight smarter, harder.
Every reinforcement that arrived whispered his name under their breath.
Even so, his main body never strayed far from Tsunade.
He could still remember that one moment, that accidental strike to her softness, her plumpness that marked her in his mind forever.
There was no chance he would let her be left exposed now.
Kumo noticed. Some Elite Jōnin already shifted toward him, toward her.
They had seen the way Katsuyu's countless tiny bodies littered the field, not only healing wounds but also feeding chakra back into Konoha's side for potentially unlimited offense.
The longer the battle dragged on, the more dangerous it became for them.
If Tsunade wasn't cut down, their numbers and firepower would eventually mean nothing against the constantly recycling force.
Ryusei grinned as he felt the concentration of killing intent bearing down on him.
He knew they would come.
But his eyes flicked toward the Katsuyu fragments hidden near him, humming faintly with stored chakra.
As long as the chakra wasn't the problem, he could keep fighting.
The only way they got him now is if enough of their elites gathered on him to crush him in one blow, instead of coming at him endlessly with attrition in weaker formations.
The more he thought about it, the clearer it became: Kumo had no idea what Tsunade was truly capable of now.
They believed this was the same woman who only healed in the shadows, not the one who could power entire battalions for days.
Maybe she didn't have it during the last war?
Not to mention all those rumors about her neutered ability as a fighter that even most people in Konoha believed.
So there was no way Kumo could have known.
That mismatch with reality could turn fatal.
It was the best opportunity for their side to win right now.
Still, Ryusei didn't let the grin fool him.
Inside, his thoughts were sharp.
One mistake against the Raikage's sons, Tsunade makes, one concentration of too many Elite Kōnin against him at once, and everything would collapse.
His life, Tsunade's, the Den, the entire front.
There was no margin for error.
That was why he stayed at her side.
The enemy would surely update their view and try to focus more and more on her and, hence, himself by extension.
That was why, even in this chaos, he perfectly followed the plan the three of them had carefully devised for this critical, defining moment that comes a few times in shinobi life.
Shield Tsunade from more pressure.
If successful, it was a perfect victory on their record and an enormous reputation boost.
If not, then they could lose their lives here inside those dark tunnels, literally at any second.
The surprising thing about Katsuyu's fragments was that they weren't just something Ryusei had already seen firsthand when one saved his life; they could also conceal both their chakra and physical presence remarkably well while split into those smaller "batteries."
Kumo was discovering that now the hard way.
They were almost impossible to deal with directly, and Tsunade had already produced plenty before the enemy even breached the Den.
'Katsuyu was truly the most versatile and durable summon out of them all...'
So what option was left? Ryusei knew they would figure it out eventually.
To remove such a troublesome summon, the only answer was to kill its caster.
That was why he felt the battle would come down to this: could Konoha's forces exploit Katsuyu's advantage to break the enemy lines fast enough, before enough of Kumo's elites grouped here together to eliminate Tsunade? This was what worried Ryusei the most now.