Inside the volcano, the artificially excavated cavern had descended into chaos.
The space was massive, carved deep into the volcanic rock over years of work. Various experimental devices were scattered throughout. Glass containers held specimens floating in preservation fluid. Several researchers in white coats ran between workstations.
Along the walls, iron chains held captured beasts in place. A three-headed dog snarled and thrashed against its bonds. Something that looked like a cross between a bear and a lizard clawed at the stone floor. The creatures sensed danger and were trying to escape.
At the center of the cavern sat a massive tank, easily five meters tall and three meters wide. Inside, green nutrient fluid bubbled and churned. And floating in that fluid was something that shouldn't exist. The creature had a bloated, vaguely humanoid body covered in purple-gray skin. Two thick tentacles extended from each side of its abdomen, each one nearly two meters long and covered in sucker-like mouths. Its head was misshapen, eyes positioned asymmetrically across the skull. As it stirred, the nutrient fluid began to glow.
Then its eyes snapped open.
"ROOOOAAAAAR!"
The roar shook the entire cavern. Loose equipment crashed to the floor. Cracks spider-webbed across the tank's glass. And a surge of violent, chaotic chakra exploded outward, washing over everything in the chamber.
"No! We can't control it!" one researcher shouted.
The creature's tentacles smashed through the glass. Nutrient fluid gushed out across the floor as the thing pulled itself free from its containment. It was even larger than it had looked in the tank, standing nearly four meters tall when fully upright.
"Run!" another researcher screamed.
They bolted for the cave entrance, white coats flapping behind them as they ran. But the creature moved with horrifying speed for something so large. One of its tentacles shot out like a spear, crossing the distance in a heartbeat.
SQUELCH!
It went straight through a researcher's chest, emerging from his back. The man had maybe a second to look down at the tentacle protruding from his torso before it yanked him backward. His scream cut off abruptly as the creature's body opened like a mouth and swallowed him whole.
"Honoka! Seal it! Start the sealing technique now!!" the surviving researchers shouted desperately.
A red-haired girl crouched beneath the tank platform formed hand seals with shaking fingers. She was maybe fifteen or sixteen years old, wearing a torn lab coat over what looked like civilian clothes. Her hands moved through the sequence rapidly.
Golden light erupted from beneath her feet. Sealing formula spread outward in complex geometric patterns, glowing characters rising from the stone floor and reaching toward the creature like chains. The formations wrapped around its limbs and torso, attempting to bind it in place.
Around her, more screams echoed through the cavern. Another researcher got caught by a tentacle. This time the creature didn't bother pulling him in, just slammed him against the wall hard enough to leave a red smear. A third person tripped while running and the monster crushed him underfoot.
"Honoka, do something! Stop it!"
But the creature was adapting. The moment the sealing chains made contact with its body, they began to dissolve. The golden light dimmed and flickered. The thing was absorbing the chakra directly, feeding on the very technique meant to restrain it.
"I can't hold it!" Honoka cried out. "It's too strong!"
The sealing formations grew thinner and weaker with each passing second. Then, with a sound like breaking glass, they shattered completely. The golden sealing exploded into glittering fragments that rained down across the cavern floor.
Within thirty seconds, nearly every researcher in the chamber had been killed. Some eaten, crushed, or simply torn apart. Blood painted the walls and pooled on the stone. The captured beasts in their chains had gone silent, cowering as far from the creature as their bonds allowed.
Only Honoka remained alive.
The creature turned toward her. Both tentacles drew back.
She stumbled backward, her heel catching on a piece of debris. She hit the ground. Looking up at the monster looming over her, she knew she was about to die.
The tentacles shot forward.
She closed her eyes, tears streaming down her face. She didn't want to see it coming.
But the expected pain never arrived.
Instead, wind rushed past her face as she was pulled away at incredible speed.
"I made it just in time."
Honoka slowly opened her eyes and looked up.
The man holding her had short blonde hair and sharp features. He looked maybe early twenties.
Her face immediately flushed red. Even in the middle of a life-or-death situation, her brain decided this was the perfect time to notice how attractive her rescuer was.
Kenji had grown used to this reaction over the years. In his previous life he'd been unremarkable, the kind of person who blended into crowds. But the Yamanaka clan apparently had excellent genetics. Combined with years of ninja training keeping him in peak physical condition, he'd ended up considerably better looking than your average shinobi. And rescuing someone from certain death tended to trigger a predictable response, regardless of how cliché the scenario was.
"ROOOAAAAR!"
The creature roared again, furious that its prey had been stolen. Both tentacles lashed out toward Kenji simultaneously.
He shifted his weight and blurred to the side. The tentacles slammed into the spot where they'd been standing, cracking the stone. He landed ten meters away, still holding Honoka, and took a moment to properly observe the creature.
This had to be the Summoning Island from the filler arc. Also called the Forgotten Island, a place where researchers had been conducting illegal experiments on ninja beasts. And this thing was their failed masterpiece, the so-called Ultimate Summoning Beast that could absorb other creatures' abilities.
Emphasis on "failed."
"It's the Ultimate Summoning Beast we created," Honoka said quietly from his arms. "It can devour other ninja beasts and absorb their chakra and abilities..."
"I figured," Kenji replied, studying the creature's movements. "But I can tell it's not complete yet. Something's off about its chakra flow. And more importantly... it's ugly. Even if it were strong, I wouldn't want it."
He set Honoka down behind a large piece of equipment.
"Stay there."
His hands moved through seals.
Iron sand erupted from the volcanic rock walls, drawn by his magnetic chakra. The particles swarmed together in front of him, compressing into a solid barrier maybe three meters tall and two meters wide. The surface hardened until it resembled polished metal.
BOOM!
Both tentacles slammed into the shield simultaneously. The impact was massive. But the iron sand held firm, absorbing and distributing the energy across its structure. The creature roared in frustration and struck again, achieving the same result.
"Iron Sand Drizzle!"
The shield exploded outward. The iron sand separated into thousands of tiny projectiles. They filled the air, converging on the creature from every angle.
The thing tried to dodge but there were too many projectiles coming from too many directions. They tore into its body, punching through the thick skin and shredding the flesh beneath. The creature's roar turned into a shriek as explosions rippled across its form wherever the iron sand made impact.
BOOM! BOOM! BOOM!
Smoke and dust filled the cavern, obscuring the creature from view.
"Is it dead?" Honoka asked nervously, peering around the equipment she was hiding behind.
"No," Kenji said, his chakra sensing locked onto the target.
When the smoke cleared, the creature's condition became visible. Its bloated body was riddled with holes, blood leaking from dozens of wounds. Half its head had been blown apart, revealing the skull beneath. But it was still moving, still trying to stand up.
He was preparing to finish it when the creature's abdomen suddenly split open vertically. A tearing sound filled the cavern as something new emerged from inside the original body.
The new form resembled a gigantic fly, maybe three meters long with a bulbous abdomen. That abdomen bore a massive mouth filled with rows of teeth. Its head was wrapped in thin tentacles that writhed constantly. Translucent wings buzzed on its back.
It just keeps getting worse. If someone summoned this thing in battle, the enemy would probably die from shock before the fight even started.
The fly-creature's tentacles shot toward him. He dodged, pulling a kunai from his pouch and hurling it at the creature as he moved. The blade embedded itself in the volcanic rock wall behind the monster.
1 second...
His left arm grabbed Honoka again, pulling her close. His right hand formed the Rasengan, blue chakra spinning and compressing into a perfect sphere.
2 seconds...
Space bent, and he was beside the kunai, directly behind the creature. He slammed the Rasengan into the mouth on its abdomen.
"ROOOOAAAAAR!"
The creature's shriek was piercing. The Rasengan tore into its body, the spinning chakra drilling deep and shredding internal structure. The force of the impact launched the thing backward, sending it crashing through the metal gate at the rear of the cavern.
It tumbled through the opening and plummeted toward the lava pool at the volcano's core.
"Is it finally dead?" Honoka asked, staring at the glowing red pool below.
"Probably not," Kenji said calmly.
As if to prove his point, the creature suddenly sprouted large membranous wings from its back. They spread wide, catching the updraft from the lava's heat. The thing banked sharply and flew back toward the cave entrance, heading straight for them.
Kenji's chakra flared. Magnet Release energy poured out of him in waves, and iron sand responded to his call. It poured from the walls, the floor, the ceiling, converging in front of him at incredible speed. The particles compressed under enormous magnetic pressure, forming into a solid cylinder maybe half a meter in diameter and a meter long.
"Magnet Release: Iron Sand Cannon!"
BOOM!
The iron sand projectile vanished from sight in an instant, accelerated by multiple overlapping magnetic fields. Its velocity peaked at seven times the speed of sound. The air itself couldn't get out of the way fast enough, creating a miniature sonic boom that shook the cavern. Friction with the atmosphere heated the projectile's surface to glowing red, turning it into a stream of superheated metallic plasma.
The principle was simple, just an electromagnetic railgun translated into ninjutsu. Magnet Release provided the magnetic fields. Iron sand provided the projectile. Physics handled the rest.
SPLAT!
The red-hot projectile struck the creature's head. The skull exploded like an overripe fruit, chunks of bone and brain matter spraying across the cavern. The body went limp immediately, wings collapsing as it began to fall again.
"Magnet Release: Iron Sand Wings!"
Iron sand flowed from Kenji's back, shaping itself into two large wings that stretched maybe three meters from tip to tip. They bore him and Honoka upward, carrying them out of the cave and into the air above the lava pool. He hovered there, watching the creature plummet toward the molten rock below.
Just to be sure.
More iron sand poured from the surrounding walls, gathering in the air above the falling creature. It compressed and shaped itself into a massive pyramid maybe two meters tall, with a sharp point at its base.
He lifted his hand and the pyramid shot downward like a dropped anvil. It struck the creature's ruined head, driving the body down faster and punching it deep into the lava.
HISSSSSS!
The sound of flesh burning was horrible. The creature's scream grew weaker and weaker until it finally dissolved into smoke, disappearing completely into the bubbling molten rock.