The hidden door sighed open and the Underworks fell away.
Cold, filtered air poured over them. Beyond the threshold stretched a white corridor- rounded corners, soft floor-glow, no seams, no pipes, no rust. The hum here was tight and even, the sound of machines that had never been allowed to rattle.
On either side: clear panes looking into training bays.
In the first, a track coiled like ribbon. Sections could tilt and lift; pistons under the floor pushed panels up or dropped them away so a driver learned to read a road that changed mid-turn.
In another, a climbing wall made of hand-sized tiles. Under the glass you could see little motors and rails; tiles slid, clicked, and re-locked in new patterns.
Farther down, the shooting lane. multiple shooters, different scenarios, different guns, different training, same range.
It just went on and on, as if the training would never make you good enough.
Above every room, behind dark glass, rows of monitors, and a bank of complex controls: sliders for speed and force, barely labeled toggles (all of them locked under covers), and a red STOP that had been pressed enough times to shine.
Humans ran everything. You could hear them: low voices, pencil taps, the calm of people who watched pain for a living.
Takeshi's heels stopped at the first room. It didn't have doors, as if anyone could step inside
"As far as I can recall, this is the gym" he said, though the word didn't fit the room. Racks stood precise and waiting, machines sleek and surgical, cables coiled like silver veins. Nothing sagged. Nothing squeaked. Everything looked underused - the sort of place that made effort feel like a procedure.
Someone was upside down in the center of the floor.
One arm locked, shoulder over the wrist. She dipped - nose to the floor, push, lock, again. One-hand handstand pushups as if gravity had just given up trying to argue with her. Short silver hair swung with each rep, a clean bob cut that framed a face full of mischief and trouble. When she finally noticed them, she kicked down, landing lightly. Blinked once.
"Tin arm. One eye." Her grin cracked wide. "You're supposed to be dead."
"Kori," Takeshi said, and some stone in his voice went warm at the edges.
She crossed the distance in three steps and punched his shoulder - the flesh one - hard enough that Raizen flinched for him. "You don't send a note for a decade and then stroll back in here with two strays?" Her eyes flicked to Raizen and Hikari. "Cute. You get them from a shelter or did they follow you home?"
"Strays bite," Takeshi said. "They want to learn."
Kori's gaze sharpened the way a knife finds an edge. "Wanna learn what?"
"How not to die." Came the answer
"Hmmm." She made a show of looking them over. "That's a popular course."
A pair of students, if you could call them that - worked in the background without turning. The same age as Raizen and Hikari, they didn't look much older. Kori's students, by the look of their focus. The boy stood at a lane firing a compact pistol into shifting light; the report was a polite crack, targets flickering and vanishing just as the trigger broke. The girl moved in front of a mirrored wall, practicing cuts with a steel claymore, her stance corrected by red lines that skated across the glass and beeped when her hips drifted. Neither stared. Neither had to. The Rust Room taught you to notice without looking.
Kori finally broke the silence.
"We should start with introductions, I suppose? I'm Kori. I break bad habits, egos and bones." She pointed at Raizen's bandaged hand. "That still attached?"
"Barely," he admitted.
Takeshi softly grabbed her shoulder, in a friendly manner, the room's clean light turning the scar under his patch into a pale rope. "They don't want safer lives, Kori. They want sharp ones. Give them edges."
Kori's grin turned feral. "I always do! You know that, old man!"
Turning back to the two, she slightly stopped smiling: "Let's see what you're made of."
Kori walked fast, talking as she pointed - simple, practical. They followed her in silent amazement.
"Everything here teaches one clean lesson at a time. No fancy lore. Track teaches you to commit through fear. Tile wall fixes footwork. Shooter lane kills the twitch in your trigger. they're too many to list all of 'em right now. Spoiler alert: You'll master them all, if you want a place in this world"
She tapped the glass of a booth; the woman inside glanced up. "Mina!" Kori called. "Tag two new under 'guest'. Baseline vitals only. Keep a running map on movement."
Mina flicked switches, calm and curious. "Guest profiles spinning. I'll suppose agility? What will it be??"
"Give me Reflex room Three. Load the basic starter set. Caps on force to non-break. I don't want splinters. Yet."
"Reflex Three, basic, non-break," Mina repeated, fingers quick. "Ready when you are." "Come on, youngsters!" She exclaimed while leading them through to a door stamped R-3
Inside: a white box. Ten paces by fifteen. Frosted glass floor. Blank walls. A platform marked A at one end, B at the other. A single black camera eye in the ceiling.
"Looks empty," Raizen said.
"It breathes," Kori replied, grinning again. She tipped her chin toward the booth window high on the wall.
From behind the thick glass, Mina's voice came clear. "Reading baseline. Boy's pulse high but steady. Girl's... low. Odd."
Kori rolled her shoulders. "Good. We're starting easy. Get from A to B in three minutes. Floor shifts. Walls argue. Hesitation hurts. Don't waver." She flicked the intercom. "Mina, bring it up on my count."
"Standing by."
Raizen looked at Hikari. She nodded once, with a hint of doubtness. They stepped onto the start platform.
"Five," Kori called. "Four. Oh, just go already!"
Nothing moved. The two could hear their own breathing. The soft whine of something waking far away. Then the floor dipped a breath and white beam snapped from the left wall - no color, just heat and force - and kissed Raizen's cheek. Vision went white, then red at the edges, for a split second. He tasted metal. He staggered, not being able to see anything around him. Hikari yanked his collar and pulled him down. A second beam took the space where his head had been. "Don't help me! I can stand!" Raizen shouted, full of embarrassment.
"Eyes up, Raizen" Kori laughed. "Nyx claws swing faster. You would have been dead… like what? Five times now? Don't let the room lead. Tempo's yours."
Two poles telescoped from the right wall and began great lazy sweeps that weren't lazy at all. Raizen ducked the first, ate the second on his shoulder.
Up in the booth, lines marched down monitors - heart rates, blood oxygen levels, a little heat map of where their feet had been. Mina leaned closer. "Is it a bug…?" she whispered to herself
The room stacked beams in a fast, everchanging lattice - low-high-mid-mid-high - too much to read if you chased the light. Hikari slid through gaps as if they'd been drawn for her. Raizen copied, took a line across his forearm, but quickly adapted. He kept going
Raizen swore and forced his legs to keep cadence. Hikari's face emptied - precise motion without noise, like she never had any feelings. Simple, cold, efficient.
Mina double-checked the data on other monitors.
"Latency's strange on the girl. Like, very strange."
"What do you mean?" a second tech asked.
"Predictive metrics at seventy when baseline reads one-thirty," Mina murmured. "She's moving like she knows a beat she hasn't even processed yet."
Kori wasn't listening. She was too focused on every small motion, amused every time Raizen was slapped by a beam. To her, it was funny to see him always wiggle back up, with an uncanny persevearance. Looking at Hikari, way ahead, she frowned.
As if she didn't want anyone to hear, she mumbled:
"Takeshi… Just what the hell did you bring me?"