". With the given starting conditions, I use the Fletcher-Reeves conjugate gradient method like so…" Long black hair trailed in her wake as she moved back and forth across the blackboard.

  "The gradient of the first iteration is non-zero," she continued, "so I repeat, finding the new X with the arg min of Q using the previous values of X, A, and S…" The class watched intently as she worked through the question, her chalk rapping against the blackboard through each step.

  "And on the second iteration, the gradient is zero." She set down the chalk and turned to face the class. "This is the optimal solution."

  "All correct," said the teacher. The class filled with exchanged glances between the students, surprised murmurs, and the hasty shuffling of paper as they got to taking notes. "Very well done, Erina-kun. You may return to your seat."

  "Wow, that was amazing!" Erina's friend caught up to her after class, slowing to match her pace on the way home. "How did you know any of that? Are you some kind of genius?"

  "Not in particular." Erina brushed a stray lock of hair aside with the faintest smile. "My mom assigned it as part of my studies. I happened to see it before."

  "No way," said her friend. "She's really got your nose to the grindstone, huh? Second year of high school has barely started and you're way ahead of us! How many hours a night are you sleeping?"

  "It's fine. I can manage." Erina extended her arm and focused. One twirl of her hand brought a green orb of light flickering to life in her palm. It grew upwards, extending, rotating, and splitting into increasingly greater detail until a beautiful dragon curve fractal floated in the palm of her hand. "After all, I wouldn't be able to understand how to use this otherwise."

  It was a clear, cloudless day. The sun shone brightly overhead as the two girls strolled through the city streets, passing by their favorite hangouts. Erina's friend excitedly pointed out the new clothes on sale in the display windows as they walked by. The chatter of students and the clicking of the traffic lights filled the air.

  "Ooh, do you smell that?" Her friend raised her head at the scent of freshly baked bread. "Hey, did you hear? A new cafe opened just down the street last week! Why don't we stop by?"

  "I'm sorry." Erina politely bowed. "I promised to help with cooking today, so…"

  "No problem!" Her friend looked ahead to the intersection as they arrived. Their houses were in opposite directions of the road. "'Kay, let me know when you're free!"

  "I will!" Erina waved her farewell before adjusting her bag and setting off the rest of the way on her own. Pigeons gathered on the power lines overhead, chirping at each other and at the student coming home.

  "Mom! I'm back!" Erina called, kicking off her shoes.

  "Oh, Erina! Welcome back!" Her mother poked her head through the doorway. Her white hair stood in stark contrast to her daughter, so long it nearly reached the floor, with faded pale cyan marks resembling branches of lightning or trees running down it. "We'll be starting supper soon—I just need to get this working first." A large sleek-looking machine sat in the kitchen with her, its top open to reveal the inner wiring. "Why don't you drop your things off upstairs?"

  It was a good time to get her studies out of the way too. Erina headed up, set her bag down in her room, and spun into her chair, letting it swivel round till she came to a rest facing the window. Her violin rested in its case by her tableside.

  "…Hm?" A small fuzzy caterpillar had found its way onto her windowsill in search of food. Erina scrounged up a napkin and folded it over, carefully offering the edge to the little bug.

  It got up on its back legs, seemingly feeling out the new material, and then slowly clambered on. She got up and stretched as best she could to reach the tree branch just outside the window before depositing the bug onto a nearby leaf. A pigeon chirped curiously at her from the power lines above and then took off to join the rest of its flock.

  Erina sat back down and watched the caterpillar wander the new surface before it settled down and began nibbling away at the leaf. Yup, looked good to her. She stretched her arms again, letting them relax with a refreshed sigh and then turning to her desk where her textbooks awaited. Knowing her mom, it'd take at least an hour before she noticed the time passing at best, so Erina had about that long to see how much she could get done.

  It was another peaceful day as always. As she opened her books and got to work, Erina wondered what sort of sweets and pastries she might find at the cafe. She couldn't wait to find out.

  . Huge machines connected in a vast network of pipes and cables lay still and lifeless. Overturned and broken flasks and bottles littered the tables, their contents long since dried to nothing but dark stains. Every step they took kicked up a small gray cloud. Nobody had set foot in this place for a long, long time.

  Beams of light filtered through the airborne dust, shining from the men's shoulders. A blue will-o'-wisp hovered by each of them, contained in small lanterns that focused their light forward wherever they looked.

  This content has been misappropriated from Royal Road; report any instances of this story if found elsewhere.

  "Search the area for anything valuable," said their leader. His dark hair was streaked with navy blue. Dressed in distinct suits of various muted colors and walking with the swaggering gait that advertised their profession, the gang members stuck out like a sore thumb against the ruined, desolate laboratory. Kicking the nearest machine, he barked, "And any idea what the hell these are?"

  One of the men dusted off the nearby terminal, trying the buttons to no avail. "Not yet, sir."

  "Is everything dead? Where's the power s'posed to come from?"

  "Deeper down, it seems like."

  "Well, what are y'all waiting for? Get to it!"

  The lot of them split up, wandering the dusty halls. Walls that were once smooth, sterile white had yellowed with age. Vast server rooms housing thousands of racks already had numerous pulled out or broken. Everywhere, they had to navigate around fallen ceiling tiles, overturned monitors, exposed tangled wiring and all manner of machine parts. Every lever they tried, every button they pushed—not a single thing still worked.

  "Shimizu, sir!" one eventually called to their leader. "I've found something!"

  Where every other room was connected by doors, he stood in front of a vast gateway. It was easily several dozen feet tall. The warped, twisted metal and rubble strewn all over the floor pointed to a door that had once been sealed, only to be violently forced open and torn apart.

  "That's the thousandth time today, this had damn well better be… good…" Shimizu's voice trailed off as he stepped over the wreckage and through the towering door.

  It opened into a cavernous underground space. Looking around, little more than the darkness greeted him back where he expected to see walls. Holes and cracks far, far above allowed the light of the surface to sneak in, shining down in dim rays through the black. The wind moaned in a low, hollow tone. A single thin catwalk was all they had to navigate deeper into the abyss, surrounded by empty air in every direction.

  "Chains…?" muttered Shimizu under his breath. His phantom light reflected off a huge vertical chain hanging in the dark, each individual link large enough to enclose a car. Shining the light over the edge, he could see it and several other chains holding a colossal metal box aloft in the dark.

  They advanced into the depths. More catwalks encroached on them from the dark, connecting back and forth in a mess of metal amidst these colossal steel units. Some were dark orange, coated in rust. Others bore burn marks of varying sizes. Several were partially destroyed, exposing the rooms inside. A few hung limply in the cavernous air, some of their chains broken and their contents long since spilled into the void below.

  "Hmph." Shimizu leapt, propelling himself to another catwalk some dozen meters up in one bound. The metal clattered under the impact. Another leap to the next catwalk up, and another, and another. No matter how far up he went, he couldn't find the ceiling all of these chains were attached to. "What the hell is this place…?"

  Back down he went, and then lower still. He estimated a few hundred meters' descent before something came into view, stretching across all the expanse of the dark.

  A silent ocean. It roiled and frothed, waves rising and crashing into each other kicking up plumes almost high enough to reach him far above its surface. Stirred by an unseen force, it stretched as far as he could see, just as endless as the expanse of the space above. Even as it raged, not a single sound escaped it.

  One of his men landed on the catwalk beside him. "What is all this water doing down here?"

  "Not water," warned Shimizu. "Primordial mana, ain't it? Heard the boss talk about it once or twice… turns whatever it can into more mana. One drop will melt right through meat 'n bone and fall out the bottom."

  "Sir, something's down there."

  In the midst of the ocean stood one small unit. Unlike the other boxes above, no chains held it in place, yet it remained unmoving amidst the raging seas. They couldn't tell how far it extended below the waves.

  The metal clanged as the two of them landed on its surface. Shimizu jerked his head, indicating the other to open the door. Locked.

  One well-placed kick broke the lock, sending the doors flying open to bang against the walls. A short stairway descended into the unit proper. For the first time since they entered the laboratory, they saw lights that weren't their own. Machinery lined the rooms, blinking LEDs and pulsing lines detailing the surfaces. Thick cables and tubes hung from the ceilings and stretched across the floor, all gravitating towards the centerpiece of the unit.

  A tall capsule stood in the middle of the room, connected to the machines on all sides. Resting behind the glass was a young girl suspended in solution. The liquid emitted an otherworldly emerald light, illuminating her features. Thin cables and wires hung from the top of the chamber, attached to the back of her neck under her long black hair. Dark strands of hair swayed gently in the mysterious liquid, her bangs hiding away half her face. A blazer, a pleated skirt, high stockings all of the same dark hue as her hair—she could pass for any student on her way home from high school if not for appearing in such a strange location.

  Shimizu took a step forward. "Who—"

  Beep.

  Monitors flashed to life, one after another. Streams of numbers, terminals flooding with text, a tsunami of information burst into existence all at once. One of the monitors stood out from the chaos—still, simple, with only two words to show.

  UNAUTHORIZED ENTRY.

  Shimizu rocketed back as a blast of green light struck him, smashing him against the stairs with an ugly crack. A faintly glowing liquid with a dark blue tone splattered the stairs in place of blood.

  "What the fuck?!" His lackey hastily scrambled for the stairs. Just a few steps away… just a few steps away… just a few steps away? Every step he took seemed to cover less and less ground. The room bent and distorted around him. The tiled floor grew longer and longer, pulling the stairs away from him as fast as he ran towards them.

  He turned back to the sight of seals. Spell circles lined with runes and filled with complex patterns traced themselves into existence around the capsule. His vision filled with light—

  First impact, chest. The beam of energy split into three as it punched into him, and then each branch split again, and again, and again. In a single instant, a blow to the chest erupted into a vast network of light rays, bouncing frantically through the body and exploding out behind him like a forest of lightning.

  Then it was gone, and the second body crumpled, twitching.

  Bubbles filled the capsule. The liquid inside turned to pale steam on contact with the air, filling the capsule with an opaque cloud as the solution drained away. The cables and tubes detached from her head and neck with a quiet whirr. A seam split down the glass in the middle. The halves retracted with a hiss of escaping steam, exposing its innards to the outside world. Pale green clouds billowed out, spilling onto the floor as they dispersed into nothing. The last of the solution that clung to her faded to wisps of vapor and dried away.

  For a moment, there was nothing.

  Then, a pulse in time with her heart.

  The inner layer of her dark hair lit with a faint, muted green.

  Slowly, drowsily, Erina opened her eyes—the same bright ethereal green as the now-vanished solution.