The boy stood by the altar, a thin, unassuming figure in a tattered school uniform. He didn't look like a god or a disaster. He looked like someone who should be sitting in a classroom, worrying about a math exam. But when he turned, the smile that split his face was too wide, too steady, and far too old.
Renji slowed his pace, the green light of his aura flickering with his own hesitation. He'd killed monsters the size of buildings, but this was just a kid.
"Uh, kid..." Renji started, his voice sounding hollow in the vast hall. "Where are your parents? What are you doing in a place like this?"
The boy didn't answer. He just tilted his head, looking at Renji with a pity that made the hair on Renji's neck stand up. Then, the hazel in the boy's eyes vanished, swallowed by a rising tide of ink-black darkness. A wisp of heavy smoke began to curl from his palm, smelling of sulfur and wet earth.
"So, you are the Mortal King," the boy said.
His voice was a grating resonance, a sound that seemed to bypass the ears and vibrate directly in the bone. "I can feel the energy trying to hide around you."
The pressure hit Renji like a physical weight, a suffocating gravity that made his own A-rank aura feel like a guttering candle. He stumbled back, sweat stinging his eyes.
[Identification in progress...]
[Subject: Ordinary human male. Status: Animated by High-Tier Entity.]
"He's possessed," Renji whispered. He shifted his grip on the Greatsword, his mind racing. If there was an innocent life trapped under that black smoke, he couldn't just swing.
"What is it?" Renji snapped at the air.
"Identify the thing inside him."
[Target Undefined. Data corrupted.]
Before the System could finish, the boy's hand flicked out. The black smoke in his palm lashed into a whip, fast as a strike of lightning. It coiled around Renji's throat, the cold of it biting deep into his skin, and hoisted him off his feet.
Renji dangled, his boots kicking at empty air.
"Who do you think you are?" the Oni asked, his voice a mocking hiss. "The 'Mortal King'?"
Renji gritted his teeth, the pressure in his skull building. He forced every ounce of his Necrotic mana outward. The explosion of green energy shattered the smoke-whip like glass. He hit the floor, skidding back, his chest heaving.
"Wait, kid. Let's make this simple," Renji said, holding up a hand, palms out. "Go home. I don't want to hurt you."
The boy didn't even blink. He launched a dozen jagged blades of dark energy. Renji twisted, his body moving in a blur of instinct, weaving through the lethal rain.
"I underestimated you," the Oni laughed.
The sound was high and sharp. "You're hesitating. You're afraid of breaking the vessel."
Renji's jaw ached from clenching it. The boy looked too much like Hikari. The same soft line of the jaw, the same small frame.
"What do you want with the soul?" Renji demanded, dodging another strike.
The Oni paused, the black smoke swirling around his ankles like a restless dog. "I want your head. The prophecy says that once you claim the Essence, you stop me from destroying this world. I'm just here to edit the script."
Renji stepped forward. "Who are you?"
The boy's grin widened, revealing teeth that had become jagged needles. "I am Lord Oni. The King of All Demons."
[WARNING: LORD OF THE DEMONS DETECTED!]
The fear was there, cold and sharp in Renji's gut, but he pushed it down. He had to. There was no one else.
"I am the one the prophecy speaks of," Renji said, his voice dropping into a low, steady growl. "I'm the Mortal King. And you're done here."
The Oni nodded, a spark of genuine amusement in his black eyes. "Brave. But if I kill you today, the prophecy dies with you."
Purple lightning began to crackle across the boy's skin, but Renji was already gone. Utilizing his maximum speed, he reappeared behind the Demon King. He didn't use the sword. He slammed his palm into the boy's back, channeling a sphere of flaming necrosis.
The explosion was deafening.
When the smoke cleared, the boy was gone—replaced by a scattered mess of bone and flesh on the stone floor. Renji's heart plummeted. The guilt was a physical sickness in his throat. "Oh god... what did I just do?"
Then, the floor began to twitch.
The pieces slid together with the sound of wet leather being stretched. Bone snapped into place. Skin wove itself back over the mess. In seconds, the boy stood whole again, his uniform still tattered but his smile untouched.
He moved faster than the wind. Renji's eyes couldn't track it. He felt the displacement of air and dipped his shoulder just as the red SS-rank sword carved through the space where his neck had been.
Renji countered with a heavy punch to the midsection, but the Oni caught it with one hand. The boy slammed his forehead into Renji's, a sickening crack of bone on bone.
Dazed, Renji felt a cold sting across his stomach as the red blade opened a shallow red line.
Renji stumbled back, clutching his side. Behind the boy, the body of the Abyss Lord began to pulse with a deep, rhythmic blue light.
"I'm not giving up," Renji wheezed.
He raised his broken blade. It didn't just reform; it evolved. Emerald lightning wrapped around the green energy, the hum of it vibrating through the entire hall. They crashed together.
The impact fractured the stone beneath their feet. They traded blows in a blur of light and sparks. Renji felt a sharp pierces in his shoulder, another in his thigh, the red blade moving with a malice he couldn't match.
"If I kill you," the Oni sneered, pressing the red blade against Renji's green guard, "this boy dies too. Then I return to my true form, Supreme."
The Oni pulled back and threw the sword like a javelin.
Renji raised his blade to block, but the force was catastrophic. His energy sword shattered into fragments of light. The red blade punched through his chest, the tip emerging from his back.
Renji spat a mouthful of blood, falling to his knees. The Oni reached out his hand, calling the sword back.
But Renji's hands clamped over the blade, his fingers slick with his own blood.
"Who do you think you are?" Renji laughed, the sound wet and broken. He gripped the steel, his aura exploding in a shockwave that threw the Oni back against the far wall.
The boy lost his grip on the weapon's mana.
[VITAL POINT IDENTIFIED: THE HEAD.]
Renji lunged. The Oni was already chanting, his fingers weaving a ritual to take the Essence. Renji didn't use his hands. He spun, throwing the stolen red sword in a flat, lethal arc.
It sliced through the boy's neck as easily as paper.
"No! Impossible!" the head screamed as it tumbled across the stone.
The head hit the floor, but the black eyes stayed open. The mouth twitched into one last smile. "This is not my real body," the head whispered. "You killed a vessel. But when I descend in my true form... I will destroy you, Mortal King."
The remains dissolved into a foul-smelling black mist, leaving nothing behind. Renji stood alone, clutching the hole in his chest, his breath coming in ragged, bloody gasps.
"What happens when he comes for real?" he whispered.
[BEHIND YOU.]
Renji spun, but he was too slow. A thin, pulsating blue line of energy extended from the Abyss Lord's body. It brushed his fingers and lashed out like a snare, yanking him toward the altar.
The room erupted in light. The stone monks lining the walls opened their eyes, a deep, resonant chant filling the air.
"Abyssus vocat regem suum."
The sound drowned out the world. Renji's vision snapped. He was standing in a black void, the Abyss Lord before him—a figure of impossible weight and age. The entity nodded.
"You are a true King," the Lord spoke. The voice was everywhere. "Willing to sacrifice everything. I have waited eons."
The Lord placed a hand on Renji's head.
"Receive my blessing. My power. My soul."
Energy flooded Renji. It wasn't just heat; it was the weight of history, the screams of the dead, and the authority of the void. Renji screamed as his soul was torn apart and stitched back together.
"Promise me," the Lord whispered. "Use it for what is right."
"I promise," Renji gasped through the agony.
The light faded. Renji snapped back to the hall, but he wasn't on the floor. He was floating, wreathed in a terrifying aura of violet and emerald. A pillar of light shot from his chest, piercing the ceiling of the dimension, announcing his arrival to the stars.
[SYSTEM REBOOT INITIATED.]
[MERGING CLASSES...]
[COMPLETE.]
[NEW CLASS: THE ABYSS MONARCH (RANK: TRANSCENDENT)]
Dimension of the Sages: Aetheria
Sage Valerius watched the golden horizon ripple with a distant, dark energy. His eyes narrowed, his fingers tightening on his staff.
"The prophecy is true. The Mortal King has claimed the seat. We must destroy him before the shadow spreads."
Dimension of Gehenna: The Demon Throne
Lord Oni gasped, his eyes flying open as he sat on his obsidian throne. He roared in fury, a sound that shook the foundations of the hell-realm, cracking the stone beneath his fists.
"Defeated by a mortal!" he hissed, his true eyes burning with a hatred that could consume worlds. "I will come for you, Renji Kurozawa. I will take everything you have left."