The rented merchant ship cut through the choppy, dark waters of the northern sea. Kei stood at the bow, the salt spray whipping against his black cloak. Kakashi and Haru stood silently behind him.
All three were dressed in the heavy, light-absorbing uniforms of the Avengers Alliance, their faces hidden behind mocking porcelain masks. To the civilian sailors manning the ship, the three shinobi standing motionless on the deck looked like silent ghosts.
With his vision perfectly restored, Kei knew the clock was ticking on his blind disguise. The moment the residual pigment faded from his eyes, the Hyuga elders would realize he was cured. He needed Kage-level power before that happened.
After finalizing his tactical decision to use the Box of Ultimate Bliss to force the Zero-Tails into an evolution, Kei had immediately drafted Kakashi for the extraction mission. While the exact coordinates of Hōzuki Castle were highly classified and unknown to the general public, Kei's new security clearance as a Special Jonin granted him access to the village's deep navigational archives.
"Is it true?" Kakashi asked quietly, stepping up beside Kei. His visible eye was fixed on the horizon, but his voice was heavy with complex emotion. "Has your sight truly been restored?"
Kei had only informed the captain of the successful surgery moments before they boarded the ship. Kakashi was still struggling to process the implications.
"It has," Kei smiled beneath his mask. "Shouldn't you be congratulating me, Captain?"
Kakashi remained silent for a long moment, choosing to focus on the mission details. "You claim you need a massive concentration of negative emotion to force the Zero-Tails to evolve. Are you certain this specific penitentiary holds enough raw despair to trigger the evolution?"
Having fought the Zero-Tails during the Shinnō incident, Kakashi intimately understood the dark mechanics of the beast. But he still couldn't fathom why Kei was risking an international incident by attacking a maximum-security black site.
Kei didn't answer directly. "Kakashi, how well do you know your pre-Warring States history? Are you aware that long before the Great Villages were founded, the Land of Grass was the undisputed, dominant military superpower of the continent?"
"I am aware of the historical texts," Kakashi nodded slowly. "But Kusagakure is a fractured, third-rate power today."
"The Grass Village only possessed that absolute supremacy because they controlled a weapon of mass destruction," Kei explained smoothly. "An ancient artifact known as the Box of Ultimate Bliss. That artifact is the sole objective of this excursion."
Due to its central geographical location, the Land of Grass was constantly trampled during the Shinobi World Wars. Decimated by the crossfire of the Great Nations, the Grass Village leadership was obsessed with restoring their ancient, mythic glory.
According to their oldest records, the Box of Ultimate Bliss was an artifact forged during the era of the Sage of Six Paths. The legends claimed the Box could grant any wish to the one who opened it, and that the ancient Grass ancestors had used it to nearly conquer the world.
When the Five Great Villages were established and the Tailed Beasts were distributed, the Grass Village's power collapsed. They were forced to the political fringes. But the radical factions within Kusagakure still fanatically believed that if they could unlock the Box, they could wipe the Great Nations off the map.
"But the intelligence reports state the artifact was lost centuries ago," Kakashi countered. He had meticulously reviewed the ANBU dossiers on Kusagakure before the mission.
"The intelligence reports are a deliberate, brilliantly executed lie," Kei chuckled. "The Grass Village never lost the Box. They simply buried it to prevent the Great Nations from stealing it."
Kei turned to look at Kakashi. "And the current Warden of Hōzuki Castle, a man named Mui, is the leader of the Grass Village's radical faction. He has been secretly funneling the chakra of his prisoners into the artifact for years, attempting to break the seal."
"If we do not intervene tonight, Mui will eventually succeed in opening the Box. Given the radical faction's fanatical desire for revenge... what do you think their first move will be, Kakashi?"
Kakashi's eye narrowed. "Total war. And Konoha would absolutely be one of their primary targets."
"Exactly," Kei said, placing a heavy hand on Kakashi's shoulder. "We are going to infiltrate that prison and completely drain the artifact of its power. If you look at the reality... are we not executing a preemptive strike to save the Leaf Village from a catastrophic war?"
Kakashi stared at the masked doctor, a profound sense of exhaustion washing over him. Kei always did this. He always managed to twist his dark, selfish ambitions into an airtight, undeniable moral goal.
It was glaringly obvious that Kei only wanted the Box to feed his own personal monster. Yet, he had flawlessly framed the heist as a heroic mission to protect Konoha, making it psychologically impossible for Kakashi to refuse.
Seeing the resignation in Kakashi's posture, Kei smiled beneath his mask. Recruiting the Copy Ninja into the Avengers was the greatest tactical maneuver he had ever executed. Shinobi who were enslaved by the Will of Fire were so wonderfully easy to use.
Kakashi sighed. "Even if the logic holds... are you certain you want to gorge the Zero-Tails on that much dark chakra? It is a highly corrosive, unstable energy."
"You must understand a fundamental truth of this world, Kakashi," Kei said, his voice dropping into a serious, lecturing tone. "Power itself is neither good nor evil. It is entirely neutral. The only thing that determines the morality of a weapon is the hand that wields it."
"Furthermore, if the legendary Tailed Beasts can be subjugated and controlled by human hosts... a bastardized parasite like the Zero-Tails is entirely manageable."
While the ancient legends claimed the Box of Ultimate Bliss was a divine artifact that granted wishes, Kei knew the horrific truth. The Box did not grant wishes. It was a prison.
Opening the Box released a demonic, winged monstrosity known as Satori. The beast was a biological nightmare, capable of perfectly reading the fear and killing intent of its enemies, making it virtually untouchable in combat. The ancient Grass ancestors hadn't conquered the world with wishes; they had nearly conquered it by unleashing Satori to slaughter their enemies.
Because the seal required a staggering, astronomical volume of chakra to open, the Grass Village had secretly hidden the Box beneath Hōzuki Castle, allowing Warden Mui to slowly siphon the lifeforce of the thousands of prisoners to feed the lock.
"Power itself is neutral..." Kakashi muttered, turning the philosophy over in his mind. He couldn't easily refute the logic. The village's ultimate weapon, the Nine-Tails, was currently sealed inside an innocent child. If Kakashi claimed that dark power was inherently evil, he would be condemning his sensei's son.
As the ship sailed further north, a thick, unnatural fog began to roll across the water, reducing visibility to zero.
After navigating blindly through the dense mist for an hour, the dark, jagged silhouette of an isolated island finally broke through the gloom. Hōzuki Castle. The Blood Prison.
"This is a zero-footprint infiltration," Kei commanded as the ship dropped anchor a mile offshore. "We must secure the artifact and initiate the chakra drain before the Warden realizes his vault has been breached."
Kei formed a single seal, simultaneously activating his newly restored Byakugan and expanding his sensory web to its absolute maximum limit. He leaped silently off the bow of the ship, landing lightly on the surface of the freezing water. Kakashi and Haru landed seamlessly behind him.
The island was crawling with hidden sentries and perimeter traps. But against the absolute, 360-degree x-ray vision of the Byakugan combined with Kei's sensory radar, the defenses were entirely useless.
Utilizing the heavy fog for visual cover, the trio moved like phantoms, effortlessly weaving through the blind spots in the patrol routes. They didn't need a map. The sprawling, gothic architecture of the Blood Prison dominated the center of the island, a massive fortress of black stone.
They bypassed the outer walls and slipped into the prison's lower levels. The moment they crossed the threshold, the air grew freezing cold. A heavy, suffocating aura of pure misery and despair permeated the stone.
Faint, echoing screams of prisoners being tortured drifted down the long, torch-lit corridors.
Because the Grass Village arrogantly assumed their external perimeter was impenetrable, the internal security patrols were surprisingly light. The trio advanced deeper into the fortress with terrifying speed.
As they moved, Haru kept her medical ledger open, rapidly sketching the layout of the prison blocks, the design of the heavy steel doors, and noting the patrol timings. She was meticulously gathering operational data for the Sanatorium's empty severe-treatment ward.
Kakashi noted her intense espionage but didn't say a word. He knew challenging her was pointless. While Kei kept the deepest secrets hidden, Kakashi was well aware that the Sanatorium was vastly more than a simple civilian hospital.
Soon, they reached the deepest, most secure sector of the fortress—the administrative wing directly beneath Warden Mui's office.
"Halt," Kei raised a hand. His Byakugan flared. "Down that corridor. There is a massive chamber entirely wrapped in high-density suppression seals. My vision cannot penetrate the walls."
It was the ultimate, ironic flaw of defending against the Hyuga. While advanced fuinjutsu could successfully block the Byakugan's x-ray vision, the sudden appearance of a massive, glowing black box in the middle of a fortress immediately signaled exactly where the most valuable asset was hidden.
Since they had successfully located the vault, stealth was no longer required.
Kei drew a premium explosive tag from his cloak and flicked it casually down the hall.
BOOM!
The violent detonation shattered the reinforced stone doors, blowing a massive hole into the sealed chamber.
As the smoke cleared, the objective was revealed. Sitting in the center of the dark room was a colossal, cubic artifact forged from dark, ancient stone. Carved into the four massive faces of the Box were deeply unsettling, distorted demonic masks representing Joy, Anger, Sorrow, and Pleasure.
"Captain. Haru. Establish a defensive perimeter at the breach," Kei ordered, his voice echoing in the vault. "Hold the corridor. I will extract the entity and initiate the drain."
Kei stepped into the room and threw off his cloak. With a sickening, wet tearing sound, the grotesque, mask-wearing leech of the Zero-Tails erupted from his spine, its dark chakra flaring wildly as it sensed the ocean of despair radiating from the Box.
Simultaneously, klaxons began screaming throughout the entire fortress. Dozens of elite guards were already sprinting toward the lower levels.
But the man moving the fastest, his face twisted in absolute, panicked fury, was Warden Mui.
He could not allow the Box to be compromised. His son, Muku, was trapped inside it.