"Roar—!"
The violent roar echoed through the dark mine, shaking loose debris from the ceiling.
Yoru stood his ground, feeling the heatwave mixed with the scent of sulfur and intense malice rushing toward him, yet his eyes remained exceptionally calm.
It was pure resentment.
Not a hatred directed at any single person, but a collective consciousness of countless miners who had been buried alive in the dark underground over hundreds of years, dying in despair from suffocation and high temperatures.
They feared cave-ins, they feared the dark, and they feared the searing heat of the underground lava that seemed capable of melting anything.
It was precisely this extreme fear of subterranean heat that had birthed the monster ahead, one that was about to step across the threshold of a Special Grade.
"Clack, clack, clack."
Yoru didn't draw his blade. Instead, he maintained a steady pace, continuing deeper into the mine.
As he went deeper, the surrounding rock walls began to turn a dark crimson. The air felt as if it had been ignited; every breath felt like swallowing fire.
If it were an ordinary sorcerer, or even a Grade 1 sorcerer, their lungs likely would have been scorched long ago without using cursed energy to protect themselves.
But Yoru was different.
Total Concentration: Constant.
He opened his mouth slightly, and a long, deep breathing rhythm established a perfect internal cycle within his body.
After the scorching air was inhaled into his lungs, it didn't cause any damage; instead, it acted like fuel, making his blood boil and multiplying his muscle activity.
Sun Breathing was, by nature, a swordsmanship that danced with fire and high temperatures.
"Snap."
From the darkness ahead, the grating sound of grinding bone suddenly echoed.
By the faint red light reflecting off the rock walls, Yoru finally saw what was blocking his path: a group of extremely distorted monsters.
They looked as if they were cobbled together from charred rock and withered corpses; some lacked lower bodies and could only crawl along the ground using mutated hands.
Others had flattened heads, with black sludge continuously oozing from their mouths.
These were the manifestations of the mining disaster victims' resentment—the grunts of this mine.
"So hot... so dark..."
Dozens of miner cursed spirits, like hyenas scenting blood, snarled and lunged toward Yoru.
Yoru sighed.
"Forgive me, but this is the only way I can set you free."
He slowly drew the standard-issue katana at his waist—a blade borrowed from Jujutsu High that was already severely chipped from previous battles.
"Sun Breathing, First Form..."
"Dance!"
"Swish!"
A brilliant ring of fire bloomed instantly in the dark underground!
Yoru's figure was like a god dancing amidst the flames.
The broken katana in his hand traced a beautiful arc, slashing through the dozen-plus cursed spirits at the front with incredible speed and precision.
There was no flashy clashing of cursed energy, only the purest, most ultimate aesthetic of violence!
"Squelch!"
Charred limbs flew through the air.
The cursed spirits struck by the flames of Sun Breathing didn't even have time to scream before vaporizing instantly in the extreme heat, leaving not even a trace of residual cursed energy.
This once ordinary katana seemed to have been granted life in Yoru's hands.
"Thud!"
Yoru kicked away a cursed spirit attempting a sneak attack from behind, using the momentum to flip through the air.
"Sun Breathing, Fourth Form: Fake Rainbow!"
His body left a trail of afterimages in mid-air, causing the lunging cursed spirits below to collide with each other.
Immediately after.
"Fifth Form: Fire Wheel!"
He flipped upside down mid-air!
The blade brought down a blazing wheel of fire, crashing down with the weight of a mountain!
"Boom!"
The entire floor of the mine was split open, leaving a charred crack over ten meters long!
The remaining dozens of miner cursed spirits were completely reduced to ash by this single strike.
"Phew..."
Yoru landed steadily and exhaled a puff of white air.
However, just as he was about to move forward.
"Crack!"
A crisp snapping sound came from his hand.
The Jujutsu High katana finally gave out, unable to withstand the terrifying heat of Sun Breathing and Yoru's explosive strength. It snapped clean off at the hilt, turning into a pile of scrap metal.
"I guess it really wasn't enough."
Yoru shook his head helplessly, looking at the bare hilt in his hand.
Without a proper blade, he couldn't even display half of his true strength.
In his prime, he might have been able to unleash sword qi with just a finger, but right now, that was still out of reach.
"I'll just have to check ahead."
Yoru tossed the hilt aside and continued toward the deepest part of the mine.
The temperature rose higher and higher.
The surrounding rock walls were no longer dark red but instead pulsed with a heart-pounding scarlet glow.
When Yoru turned a corner, his view suddenly opened up.
It was a massive underground cavern. At the bottom, dark red lava swirled and bubbled!
In the center of the lava pool, there was a raised stone platform.
On the platform, a crystal about the size of a human head hovered quietly, emitting an eerie red light.
"Scarlet Ore!"
Yoru's eyes brightened instantly.
Even from dozens of meters away, he could feel the terrifying heat contained within that ore.
It was a Special Grade cursed object material, nurtured over centuries as it absorbed the spiritual energy of the earth's veins and the fires of despair from countless dying miners!
It was undoubtedly the perfect material for forging a Special Grade cursed tool!
However, just as Yoru prepared to approach the platform.
"Gurgle... gurgle..."
The lava pool below suddenly began to boil violently.
A suffocatingly massive figure slowly rose from the lava.
It was a terrifying cursed spirit over ten meters tall!
Its body was composed entirely of dark red lava and black obsidian. With every breath, it exhaled lethal toxic gas and sparks.
This was a Semi-Special Grade cursed spirit—the Lava Cursed Spirit—born from humanity's extreme fear of subterranean heat and lava!
"ROAR!!!"
The Lava Cursed Spirit let out a deafening roar.
Its massive palm slammed into the lava pool, kicking up a lava tsunami over ten meters high that surged toward Yoru like a tidal wave!
"Troublesome."
Yoru frowned slightly as he watched the lava tsunami, capable of melting steel, approach.
He was currently unarmed. If he tried to tank such high-temperature physical lava with his body, even with the protection of the Slayer Mark, he would be severely injured.
Retreat?
Impossible.
The word 'retreat' did not exist in Yoru's dictionary.
"Since I don't have a blade..."
A flash of madness crossed Yoru's eyes.
He took a deep breath and pushed off with his legs!
"Bang!"
The hard rock ground shattered under his feet, and his body shot forward like a cannonball. Instead of retreating, he charged straight toward the incoming lava tsunami!
"Transparent World, open!"
Yoru's eyes instantly lost focus, and the entire world turned into transparent lines and energy flows in his vision.
He precisely captured the weakest point in the lava tsunami.
At the very moment he was about to be swallowed by the lava, Yoru's body twisted incredibly in mid-air, somehow slipping through that narrow gap!
"Roar?"
The Lava Cursed Spirit was clearly stunned that this human had managed to dodge its attack.
And in that half-second of distraction...
Yoru appeared above the stone platform like a ghost!
He reached out his right hand and grabbed the Scarlet Ore that was radiating terrifying heat!
"Sizzle!"
The sound of searing flesh echoed the moment his palm touched the ore.
Even with Yoru's monster-like physique, he couldn't completely ignore extreme temperatures of this level.
But Yoru didn't even flinch.
"System!"
"Establish a Binding Vow!"
[SYSTEM: "TEMPORARY SHAPING" BINDING VOW ESTABLISHED:]
[SYSTEM: CONTENT: ACTIVATE TEMPORARY SHAPING FOR 10 SECONDS, FORCIBLY RESTRUCTURING THE SCARLET ORE INTO A BLADE BLANK FORM.]
[SYSTEM: COST: THE ORE WILL REVERT AFTER 10 SECONDS, AND SYNCHRONIZATION RATE WILL DECREASE BY 3% (CURRENT SYNCHRONIZATION RATE...).]
"Boom—!"
The moment Yoru's palm touched the ore, the extreme heat accumulated by the underground lava for centuries seemed to find an outlet, flooding into his body.
This resonance of extreme heat completely tore through the final shackles within Yoru at that moment.
[SYSTEM: EXTREME FIRE ELEMENT RESONANCE DETECTED. SYNCHRONIZATION RATE BREAKTHROUGH: 40%!]
[SYSTEM: UNLOCKED: SUN BREATHING FORMS TEN THROUGH TWELVE AND THE SLAYER MARK!]
In an instant, a deep crimson mark resembling flickering flames appeared on the left side of Yoru's forehead.
His heart rate spiked to over 200 beats per minute, his body temperature soared to 39 degrees Celsius, and his blood boiled like lava.
"Transform for me!"
Under the immense power of the 40% synchronization breakthrough and the forced intervention of the Binding Vow, the incredibly hard Scarlet Ore became like clay being molded by a god in Yoru's hand.
It stretched and restructured in an instant.
In just one second, a rough blade blank—completely crimson and radiating destructive heat—was held firmly in Yoru's hand!
"Now..."
Yoru gripped the blade blank. In those final ten seconds of the limit, he whirled around, looking down from mid-air at the shocked and enraged Lava Cursed Spirit below.
"I have a sword."
"Sun Breathing, Tenth Form..."
"Beneficent Radiance!"
"Boom!"
A full-power strike after the Slayer Mark's awakening, paired with this blade blank condensed from extreme temperatures, transformed into a massive descending spiral of fire.
Like a fragment of the sun falling from the high heavens, it crashed down!
"ROAR—!!!"
The Lava Cursed Spirit let out a scream of despair.
Its proud lava armor, under the dual enhancement of Sun Breathing and the Scarlet Ore, was sliced through instantly like paper!
"Rumble—!"
The entire underground cavern shook violently.
Blinding red light illuminated every corner.
When the light faded...
The once unstoppable Semi-Special Grade Lava Cursed Spirit had been split from head to toe, then reduced to ashes in the extreme heat.
Yoru landed steadily on the stone platform, gasping for breath.
The Scarlet blade blank in his hand twisted and reverted back into the scorching ore as the ten-second limit expired.
[SYSTEM: BINDING VOW DURATION ENDED. ORE REVERTED.]
[SYSTEM: SYNCHRONIZATION RATE SETTLEMENT: 40% -> 37% (WEAKNESS PERIOD COMMENCING).]
Yoru looked down at the ore. Though the weakness from the synchronization drop washed over him like a tide, his eyes were brighter than ever before.
"The view at 40%... I've already seen it..."
He stashed the ore away, a relieved smile appearing at the corner of his mouth.
Next, he had to find that person and have this ore, which carried the power of the sun, forged into his true—
"Shiranui."