The Engineer’s Inferno
While the forest screamed, the forge waited. The Heatbox simmered, a place built to test what refused to die.
Air thick as molten glass and walls sweating red light.
Every breath clawed its way down Roi's throat like smoke laced with metal dust.
The Heatbox had been a torture chamber once, the kind used to strip the soul from a person before their skin. Roi could still smell the ghosts in the stone: burnt oil, old blood, iron rot. A scent that clung to your teeth.
Now, it was an endurance chamber for Hunters.
It didn’t ask if you were ready. Only if you’d survive.
Roi sat cross-legged at the far end of the pit, the cracked floor still warm under her palms.
Her trap. Her field. Her stage.
And there he was. Kota, framed in the pit’s entrance like a carved idol of arrogance. His body was coiled, ready to spring. Sweat sheened his arms, catching the red light, turning it the color of blood.
He stared down at her. Roi met his gaze and lifted a hand in a lazy wave.
“Yo, asshole,” she called, voice carrying sharp and clean through the warped air. “What took you so long? You couldn’t even hunt one rat? So much for being number two.”
Kota’s jaw flexed—that familiar twitch right before he let lose. She could count the seconds between anger and reply.
Then came the smirk. Ugly. Confident, like a blade turned inward.
“You mean the one unconscious with a broken leg?” His tone dripped satisfaction. “Surprised you didn’t hear her screams.”
Roi’s nose twitched. Something flashed behind her eyes, too quick to name.
Her smirk didn’t fade. It sharpened, edges folding in like heat-hardened steel..
“Oh?” She tilting her head until her neck cracked. “Didn’t quite hear that. Why don’t you come in here and say it to my face?”
Kota laughed. Once. Loud.
“I know there’s traps in there. Probably rigged to hell with your bullshit. I’ll wait for your rat friends to crawl in first. Easier that way.”
Roi leaned back on one elbow, stretching her legs out like she had all the time in the world. The stone hissed beneath her skin.
“Scared?” she asked, voice light. Almost teasing.
The grin that followed wasn’t a smile. It was a knife being unsheathed.
“Didn’t know rank two was such a bitch.”
Kota’s mouth twitched just slightly.
“…I’m not falling for your obvious provocation,” he muttered, voice tight as wire. “Who do you think I am?”
Roi stood. The movement was unhurried, almost graceful, the kind that made her control obvious. She rolled her neck, feeling the sweat slide down her spine, the air shimmer around her ankles.
Then she spat the word like it was law:
“A. Bitch.”
The pause that followed was alive.
Hot. Inevitable.
Then Kota snapped.
“Fine!”
The word cracked the heat like a whip.
“Your provocation worked!”
Mana bloomed from his hands, not quite like shattered glass yet, but dense with heat and a bright red.
His body tensed, frame bending forward like a drawn bow.
“Now I’m going to make this as painful as possible—!”
He lunged.
The ground trembled. Heat tore the air.
Roi’s grin widened, feral and gleaming.
The traps stirred beneath her feet.
She could already feel the vibration of his step, the pulse of his mana pressing into her field. Every breath she’d taken, every bead of sweat she’d shed, had been building toward this moment.
The predator came for the rat.
But down here, in the Heatbox, where pain was the only truth, Roi moved first.
Click.
The first trap snapped alive, a glyph plate flicking open like a jack-in-the-box.
Roi saw the shimmer a second before it blew.
FSSHH-BOOM!
Heat and pressure tore through the pit. Kota barely reacted. His forearm snapped up in a blur, batting the glowing sigil aside. It detonated midair, spraying molten shards that clattered against the scrap floor like burning glass.
“Of course,” Roi hissed, already dropping into a crouch. She slid behind a collapsed beam, one knee skidding through oil and dust, her hand flying to her belt. Fingers closed around the next trigger crystal—thumb already priming it.
She squeezed,
A low hum rolled through the pit. Behind Kota, a scrap plate bolted into the wall snapped open, exposing a glowing red glyph.
The blast thundered through the pit, ripping dust from the walls and snapping loose chains overhead. Kota twisted at the last second, half-turned as the shockwave slammed into him. The edge of the detonation clipped his shoulder, heat rippling across his back and scorching fabric instead of flesh.
He skidded a step, boots grinding against scrap.
“Damn,” Roi muttered, already recalculating. “Should’ve set that deeper…”
She dove behind a scorched slab of metal jutting from the ground, part of her “workshop”. A chaos of half-fused parts:glyph pads stacked like cards, coiled copper wire, broken pressure plates, and one still-glowing mana shard the size of her thumb
Her fingers moved before her mind caught up like instinct.
Muscle memory.
Trace the line. Twist the core. Slot the shard.
A snap of current bit her knuckles, then light flared. The trap primed.
Kota charged, faster than she’d expected. Heat shimmered around him, sweat rolling down his jaw as his foot landed hard, right on top of her rearmed coil trap.
Snap!
Barbed wire screamed outward, whistling toward his legs. He jumped, effortless, as the wire sliced empty air beneath his feet. His body tucked mid-spin, twisting, landing hard, right onto another pad.
Thud.
Roi’s grin twitched.
Nothing.
“Wait—what? That one was—”
Kota's foot launched forward at her chest. Roi barely rolled beneath it. As she slid past, she slapped a palm-sized electric mana puck onto his calf and yanked two loose wires together like flint and steel.
CRACKLE!
The charge surged. Electricity ripped up Kota’s leg and through his body, locking his muscles for a split second.
“Tch— you little—”
She sprinted sideways to the right of the entrance, sliding over the cracked floor, nearly tripping over a stray cable trap. The pressure pad she’d armed earlier—the one that hadn’t gone off—sat a few meters ahead, glowing a faint, wrong blue.
She tore it open mid-slide. The crystal inside was blackened, split down the middle.
Overloaded. The heat had cooked it early.
“Hurry. Hurry!”
She ripped the dead trap from its socket, smashed it against the floor until the casing shattered, then slammed a fresh mana shard into the exposed slot.
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Click—
FZZZZZT—
The lines flared white-hot.
Still nothing.
Her breath hitched. “Are you serious—?”
Kota was already there. His fist drove into her ribs. Wet. Crushing.
The impact folded her sideways and sent her slamming into the wall. Air ripped out of her lungs as she slid down, vision exploding into white sparks.
Still, her thoughts wouldn’t stop.
It should’ve primed. The charge was right. The timing—
She blinked through the haze, Kota was straightening himself.
Smoke slid off his shoulders in lazy curls. He rolled his leg once, testing it. Adjusting.
Then his stance shifted, weight back, steps shorter, eyes no longer on her hands, but on the ground between them.
The wires.
The pads.
The gaps between them.
His grin stayed, but it was different now.
Tighter. Focused.
Roi’s smile twitched, then trembled.
Her gaze flicked to the coil line she’d just tried to reset, an old habit surfacing, the itch to finish it properly.
Kota didn’t charge. He took one careful step instead, then another, placing his foot just shy of the trigger point.
Too exact.
Roi’s trembling fingers hovered over her belt.
She caught her own wrist and forced it still.
She swallowed, breath catching in her throat, but her defiant smile widened.
“Fine... let’s see who cooks first…”
The sun above poured through the open grates like molten glass, and the metallic floor turned it all into a forge, a living crucible that cooked the air itself. Every inhale scraped Roi’s throat raw, and every exhale came out as smoke.
The heat didn’t care who was stronger.
It burned both.
But Roi was alive. Alive in the chaos she built.
Her traps were singing, sharp, unpredictable, imperfect.
Hers.
“I made this,” she muttered under her breath, voice shaking with pride and adrenaline. “This pain? This chaos? That’s me.”
Her smile cracked wide across blistered lips.
“I’m not just a rat. I’m a goddamn engineer.”
She snapped a trigger and kicked a small pod forward.
The metal orb bounced twice, then split open mid-roll.
Hundreds of needle-thin caltrops burst out, glowing faintly blue, humming with mana conduction. They scattered like living sparks across the floor.
Kota barreled through.
The spikes sliced open his forearms, his knees. Small wounds, precise, but enough to sting. He grunted, barely acknowledging them and kept moving, each step flowing smoother than the last.
Roi yanked open another mechanism beside her, a folded lattice of metal and wiring designed to snap upward and cage anything that stepped inside. She twisted the valve, heard the hiss of pressure building, and smiled through the heat.
Catch. Trap. Burn.
But Kota didn’t step into the trap. He stepped past it, just enough to trigger the release timing early. The floor folded up a second too soon, slamming shut on empty air.
By the time Roi blinked, he was already halfway to her.
“Shit—!”
She spun backwards towards the entrance, kicking dust and metal shards into the air. The explosion smoke still hung thick in the chamber, a churning gray fog, hot as furnace breath. She ducked low, rolling to one knee, sliding a small disk trap beneath the haze.
She caught a glimpse of his silhouette cutting through the smog, tall, coiled, relentless.
“He’s faster than the math says,” she hissed. “No. He’s adjusting to each trigger in real time. Fucking monster.”
The thought barely formed before another of her traps went off on its own.
A chain reaction, one glyph’s residual charge leaking into another. It bursted towards Roi, searing her sleeve as she threw herself down, heat punching the air from her lungs.
Through the blinding glare, Kota stepped straight through the fire, not only a couple of footsteps away from her.
His silhouette flickered in molten orange, heat rolling off his body in waves.
His eyes stayed locked on her the entire time.
Roi didn’t hesitate. She ripped a flash charge free and hurled it.
The device burst midair, white and silver light exploding outward, sharp enough to turn the pit into a blank void.
For half a heartbeat, she thought she’d caught him.
Then a shape tore through the glare.
Kota emerged smiling, wider than before, eyes still burning, still fixed on her.
Her heart dropped to her stomach.
More traps went off, not hers. Not planned.
The heat had finally won.
Beneath the floor, warped runes buckled under the pressure, lines bleeding into one another until they shrieked.
The plate beneath Kota’s foot snapped open like a jaw. A shrapnel latch whipped upward, catching his ankle.
SCREECH! BANG!
The blast punched him sideways. Kota staggered at last, leg buckling as glowing fragments scattered across the pit. He hissed through his teeth, sweat flinging from his chin as his foot scraped hard against the floor.
A buried failsafe trap, half-melted and unstable, forced itself awake from the heat.
But Kota planted the burned leg. Hard.
Instead of recoiling, he pushed.
The blast’s recoil surged up through him and he rode it, twisting his body forward, converting the blast into momentum. He lunged out of the smoke faster than before, using the pain like a springboard.
Roi staggered backward toward her pile of parts, metal, wire, ash, nearly tripping as she reached it.
Kota was already inside striking distance now, cocking his fist back.
She ripped open a half-assembled charge, tore away the casing with her teeth, and slammed the exposed glyphs together. Blood smeared across the etched lines as they screamed to life.
“Just work—Please, Just—”
BWOOOM!!
The world collapsed inward, fire and pressure swallowing the space between them as the trap went off prematurely. Smoke detonated outward as the blast hurled them apart in opposite directions.
Her back slammed into the floor, breath punched clean out of her lungs. Her ears rang, high and shrill. Hair plastered to her face, soaked with sweat and ash, she coughed hard, every breath tasting like copper.
Across the haze, Kota skidded to a stop several meters away, boots carving molten lines through the warped metal floor. His shirt hung in tatters, skin scored and burned. A thin line of blood ran from the corner of his mouth.
He wiped it away with his thumb. Then smiled, confidently.
"Almost got you there." His eyes sharpened into something predatory as he coiled into another lunge. "Your traps won't last forever. Its only a matter of time!"
She could barely keep her eyes open. The whole pit felt alive now. A storm of wires and smoke.
But her mind...
Her mind was still racing.
Why... Why is everything falling apart!
Her fingers fumbled through the last glyph case in her pouch. She grabbed whatever was left: a cracked mana rod, a bent pressure plate, half a battery cell from her earpiece.
No plan. Just instinct.
Build. Hope. Pray it explodes toward him, not her.
She jammed the pieces together.
Then—
A hand shot out of the smoke. It clamped around her throat before she could react.
Her eyes widened. "S-Shit!"
The world narrowed to heat, pressure, fingers of iron. Kota pulled her in slowly, almost gently, close enough for her to see every cut across his skin, the steady pulse in his neck.
His eyes were untouched.
Cold. Focused.
“He’s still not tired…?” she spoke, fighting the pressure on her windpipe.
He leaned in, voice low, steady.
“That was kinda fun y’know,” he laughed, breath hot against her cheek, “Surprisingly good training.”
The grin that followed wasn’t pride. It was something worse, boredom.
“I’ve been hit by monsters five times my size. Did you really believe your traps would to any real damage to me?” he said, tightening his grip until her vision blurred at the edges.
Kota’s hand was iron around her throat, steady and merciless.
Her boots scraped uselessly against the scorched floor, toes kicking for leverage that wasn’t there. Air refused to come, every breath a dry, panicked pull that gave her nothing back.
She clawed at her belt and came up with a fistful of parts: a thumb-sized mana shard ground thin from reuse, a loop of scorched copper wire, a cracked glyph wafer she’d never bothered to discard. Scrap. Leftovers. The kind of thing she’d turned into miracles all night.
Her fingers shook as she jammed them together between their bodies, wire biting into her skin as she twisted.
Please...
The makeshift trap sputtered. The rune flared weakly, flickering like a dying coal—
Then went dark.
A soft, pathetic crackle. The shard had burned dry.
Kota watched it failed, didn't even try to stop her.
Kota lifted her higher, the muscles in his arm barely flexing.
“Don’t worry,” he said, his tone calm, almost conversational. “Won’t kill you, obviously."
Cartilage creaked. Pain bloomed hot and sharp along her neck.
“But this?” he continued. “This is going to hurt until you pass out. Just as promised.”
Her lungs screamed for oxygen; her chest spasmed, desperate for a single gulp. Her hands clawed at his wrist, nails digging into skin, but he didn’t even flinch.
The heat pressed in. The world shrank. The forge around her became nothing but sound, the low roar of burning metal, the hiss of her own blood in her ears.
And still...
Her eyes locked on his, shaking but fierce.
Her throat barely worked, but she forced the words out.
“Still.”
“A.”
“Bitch.”
The words rasped out dry, broken.
Kota smiled like someone hearing a joke they didn’t expect to like.
“That’s more like it,” he said softly.
Roi’s defiance flickered on her lips, but inside, something fragile cracked.
Her lungs hit that final edge, the point where the body stops fighting. A strange calm washed in, a false stillness, like sinking underwater. Her heartbeat thundered in her ears, then slowed, each beat heavier, further apart.
Her thoughts broke apart, skipping like damaged film.
Don’t wanna—die. Know he won’t— kill me —But —still feels—
Her arms slackened. Her head tipped forward.
Can’t— Shouldn’t have— I'm—sorry, everyone...
And then, a name, clear as a whisper through the noise in her mind.
Kenny.
Then more, rising unbidden.
Nobu.
Dozai.
All of them refusing to fall. Especially Rei, who just put her body on the line to give them all this chance.
Rei...
The dark thickened, pulsing in time with her slowing heart. Still, she moved. Just barely.
Her fingers curled, weak but stubborn along Kota's forearm.
Will too— fight—till the bitter—end.
Kota watched her, something bubbling in his chest as his smile faltered, noting the same stubborn fire as the other rat.
His jaw set, then shifted, like he was biting back something that didn’t fit the moment.
“All you rats fight so desperately…” he said, tone light at first—too light, until it gradually became more rageful with each passing word. “Like it'll change anything… Do you guys have any idea—”
“KOTA!!!”
The shout ripped through the smoke, raw and furious.
Impact slammed into Kota’s ribs, pure mass and momentum. The sound pounded sharp and ugly, like bone meeting stone. His body twisted mid-turn, breath tearing from his chest as he was driven back.
His grip broke. Roi dropped.
Her body hit the ground hard enough to jar her back into her skin. Air crashed into her lungs — sharp, wet, burning. She coughed, gasped, clawed at her throat. The first breath felt like drinking knives, the next like drowning in heat.
Through the haze she saw movement. Kota staggering back, boots scraping molten dust.
And in front of her, blocking the heat, the light, everything—
Kenny.
He stood between them, chest heaving, eyes alive with something raw and furious.
Roi tried to speak, but all that came out was a rasp.
Kota straightened, rubbing his mouth, and grinned like a wolf.
“…Finally,” he breathed. “The other rats arrive.”
He tilted his head, gaze flicking between them, savoring the moment.
“You like the gift I left you?” he went on lightly. “Took my time with that one. Crack by crack.”
Roi’s vision tunneled, but her eyes stayed on Kenny.
On the way his smile was gone.
On the way his eyes didn’t blink.
On the way he was staring at Kota like something inside him had finally, quietly broken.
