The moment Karl's thumb pressed the USB port three times, the Drive Regulator purred like a heartbeat skipping rhythm.
"Pressure coils stabilized… oh, Karl," Agnes's voice fluttered through the comms, dripping with delight. "You're really pressing all the right buttons today~"
Each click rippled through his spine like an electric heartbeat.
The Drive Regulator on his waist flared to life, exhaling a steady vrrrrm that deepened into a predatory growl. Blue runes raced along his armor seams, tracing paths of light over his thighs and hips until the entire lower half of his body shimmered in liquid cobalt.
Then came the first tremor.
His armor loosened — not detaching, but breathing. The nanite plating across his legs shifted like a living muscle, sliding open along invisible seams. Tiny micro-gears emerged beneath, spinning in slow rotation as if testing the air.
Karl's grip tightened around the ignition dial.
Every instinct screamed caution — every cell in his body trembled under the unfamiliar strain.
But then came her voice.
"Mm… Karl~," Agnes cooed through the neural channel, her tone dripping with a velvet satisfaction that curled at the edge of his nerves. "You pressed it perfectly. Do you feel that hum under your skin?"
He could.
It wasn't just vibration — it was resonance. His bones sang with it. The Engine Soul's core pulsed like a heartbeat, syncing with the Drive's mechanical rhythm.
"I feel it," Karl muttered, his voice rasping through the helmet's filter. "Feels like my body's—"
"—becoming an instrument," Agnes finished, purring. "Your frame is aligning. Let it breathe. Let the nanites stretch. Don't fight them."
As she spoke, the orbiting armor plates began to detach — one by one — rotating in perfect synchrony around his legs. They moved like petals, each etched with glowing channels that spun faster the longer he held his stance.
From the ground up, his boots hissed steam. The asphalt beneath him started to crack, unable to contain the mounting rotational pressure.
The sound of shifting gears layered over his breathing — a hundred tiny engines spinning in harmony.
"Vythra compression at eighty-four percent," Agnes whispered, half to herself, half to him. "Torque curve stabilizing. But if you want more power…"
"Don't even say it."
"...rev me harder~."
Karl groaned, both in focus and frustration. "You're enjoying this too much."
"Of course I am," she replied, laughter like static silk. "You're literally inside me right now, Karl. The least I can do is enjoy it while you're tuning my circuits."
He ignored her, eyes narrowing on the horde ahead — the Erebions crawling out from the crack, their flesh mutating, limbs snapping into new shapes with each shriek.
The ground quivered with every one that emerged, their forms glistening in half-melted metal and viscous ichor.
Agnes's sensors pinged in his visor — a dozen red outlines flickering, then merging into chaotic motion.
"They're evolving," Karl muttered.
"They're adapting," Agnes corrected softly. "Their energy signatures… strange. Almost familiar. Like—" she hesitated, voice losing its playful lilt for the first time "—like they've tasted something of yours before."
Karl's gut twisted. "Nanites?"
"Maybe. Or maybe the cracks remembered you before you even came back."
Her voice turned low again, sultry but now lined with tension.
"Either way, you're running out of time, darling. If we're going to end this… let's end it spectacularly."
The micro-gears along his thighs spun faster, generating a visible aura of wind and light.
Loose gravel began to levitate around him.
A cobalt corona spread from his boots outward, searing the concrete into glowing veins.
Agnes whispered, "Engines are singing. Pressure at one hundred and nine percent. The lattice can hold for five… maybe six seconds."
Karl gritted his teeth.
"Then let's make it count."
"Agnes, keep me balanced!" he barked, heat roaring up his core.
"Mmm~ I am," she teased, voice vibrating in sync with the regulator's hum. "Your drive's spinning beautifully, Karl. Just… rev me harder next time—you'll draw more Vythra that way~"
The armor pieces around his legs vibrated violently — their edges glowing as bright as arc welds. The detached segments began to orbit tighter and faster, forming a gear halo that pulsed with rhythmic bursts of blue lightning.
Inside the storm of energy, Karl's body was a blur — every muscle fiber aligned with the nanite torque feedback, his nerves screaming, his heart matching the engine's rhythm beat for beat.
Agnes's voice dipped low, almost like a whisper against his ear.
"You're right there, Karl. You're perfect right now. Feel the drive's pulse… align with it. Don't resist."
The Engine Soul within him hummed, warm and steady — his mother's guiding essence tempering the surge.
The Gear Drive calculated torque ratios in the background — his father's logical rhythm balancing the madness.
And at the center of it all, Kurogane Karl stood — the culmination of two souls and one machine, vibrating at the edge of collapse.
Agnes's voice softened into a coo.
"Do you hear that? That's not the wind, Karl. That's your Drive howling. The sound of momentum begging to be unleashed."
Karl lowered his stance, right leg bent, left extended — the classic strike form, adapted from the Kamen Rider archives. Sparks cascaded off his armor.
His vision locked on the first Erebion charging through the debris — a sinewy, spiderlike beast roaring with a mouth full of grinding teeth.
Agnes sighed, content and electric all at once.
"Mmm… Karl~"
"What?"
Her voice dipped into a playful hum, vibrating through the commline.
"Are you ready~?"
He twisted the ignition dial.
The regulator screamed.
The halo of gears condensed.
And the ground cracked open beneath his feet—