The ruins held countless relics of a bygone era.

  From trivial trinkets to critical infrastructure components, a vast array of relics was unearthed by excavation vehicles and traded at high prices in the lower city's exchange.

  Water purification pods capable of cleansing contaminated resources, nanomachine programs that converted toxins into electrical energy, raw materials for the jelly packs that relic hunters consumed as sustenance—these relics were both a lifeline for the lower city's residents and the root of many deadly conflicts.

  The discovery of relics that improved daily life was not inherently bad. However, such finds were exceedingly rare. Most relics unearthed were weapons or armaments: laser rifles with damaged beam-focusing components, assault machine guns with shattered barrels, high-density carbon armor scarred by bullet marks.

  For some reason, relics found in the shallow to mid-levels of the ruins were predominantly tools of war, often half-destroyed or heavily damaged. Whether they were remnants of a great battle or a massive riot was unclear, but the weathered bones and bloodstains splattered on the walls made such grim speculations inevitable.

  Indeed, when Danan, led by Eve, surveyed a room with its electronic lock forcibly disengaged, he couldn’t help but catch his breath.

  “Now, pick any arm you like. Gear up here,” Eve said.

  “…”

  “What’s wrong? Hurry up.”

  “Easier said than done.”

  What could he say? Gazing at the array of pristine mechanical arms, Danan picked up a firearm and a piece of armor from the weapon rack, letting out a sigh of awe.

  “Eve.”

  “What?”

  “Is there… any equipment or machinery for attaching a mechanical arm?”

  “Nope.”

  “…”

  “Don’t give me that look. I’ll attach the arm for you myself.”

  “Without equipment or tools, how exactly—”

  Before he could finish, Eve’s silver wings extended from her back and pierced into the connection point of Danan’s mechanical arm. A searing pain coursed through him as his nerves and flesh were manipulated, and he tossed a black iron mechanical arm toward her.

  “Oh, this one?” Eve asked.

  “That’ll do.”

  “Sorry, but this one’s no good.”

  “Why not?”

  “This arm was abandoned during its prototype phase. The reason, if I recall, is that it triggers a connection authentication error during attachment.”

  “An error?”

  “Yes. A mechanical prosthetic works by connecting the mechanical and biological parts through neural interfaces, allowing the user to control it freely. But the brain’s electrical signals activate the arm’s response program, using artificial nerves and synthetic blood to extend the functionality of the missing limb. The error this arm produces is a reverse rejection reaction. In simple terms, if someone without the proper authentication code tries to use it, their brain gets fried.”

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  “…”

  “So, what’s it going to be? Want to stick with this one? I’d recommend choosing a different arm.”

  Staring at the mechanical arm dangling limply in Eve’s grasp, Danan said, “That one’s fine,” and turned his right shoulder toward her.

  “Have you lost your mind? I just explained—this arm requires an authentication code.”

  “I’ve got Lumina’s bugs.”

  “…”

  “Lumina’s bugs will repair any brain damage, and while they’re at it, you rewrite the arm’s authentication code. What’s that? After all your lecturing, are you saying you can’t do it?”

  “Bold move. Fine, I’ll attach the arm. Just try not to break it, Danan.”

  The mechanical arm was connected to Danan’s shoulder, where the human-machine interface fused his blood with the arm’s synthetic blood.

  “…Nothing’s happening,” Danan remarked.

  “That’s impossible…” Eve muttered. “Give it a moment. I’m checking the arm’s error logs and your biological responses.”

  It shouldn’t be this quiet. This arm wasn’t supposed to comply so easily. Eve’s eyes scanned the prosthetic’s data, rapidly processing the logs streaming from bottom to top. She paused, pressing a finger to her lips in thought.

  “What’s wrong?” Danan asked.

  “Nothing… Never mind. Good for you, you’ve got yourself a new arm.”

  Eve’s silver wings tapped Danan’s back, causing him to stumble slightly. He stared at the black iron arm, flexing its fingers, then connected a goggle cable to it, pulling up a list of its embedded functions.

  Small arms storage slot, information terminal control system, ultrasonic blade, mechanical arm expansion and update functions, and an unidentified software program… Even a cursory glance revealed capabilities far surpassing the mechanical prosthetics circulating in the lower city.

  The arm torn apart by Kaas had been high-performance, but this one was on another level. Satisfied, Danan grabbed a firearm from the weapon rack, testing its weight and feel in both hands.

  “…”

  “Why so quiet?” he asked.

  “Nothing, just thinking. Hey, Danan, have you ever—”

  Been here before? Eve was about to ask when the sealed door creaked open with a distorted groan.

  “Enemies? Perfect timing to test this arm,” Danan said.

  “…”

  “What’s on your mind, Eve? Let’s engage.”

  “…Right, let’s do it.”

  A box-shaped mechanical weapon, equipped with a rotating red siren, an electric saw on its right arm, and steel claws on its left, fixed its single-lens camera on Danan and Eve, its treads grinding into motion.

  Autonomous lethal weapon “Rindo.” Designed for unknown purposes, Rindo was meant for unmanned forestry operations on desolate lands. Upon detecting a heat signature, it indiscriminately wielded its arsenal, and if it deemed a target unkillable, it unleashed a flamethrower—a flawed function for what was supposedly a work machine, not a weapon.

  Danan dodged the electric saw as it swung upward and crashed into the ground. Drawing his blade, Helles, he used the arm’s auto-aim function to fire a bullet at Rindo’s single-lens camera.

  Rindo’s movements were predictable, but the risk of its flamethrower increased with time. The solution was simple: destroy it before the flames could be unleashed. Danan was used to this. He’d been down this road before.

  With its camera destroyed, Rindo lost its heat detection and vision. Its sharp claws grazed Danan’s head as it lunged toward Eve. The girl sighed briefly, then flapped her six silver wings, shredding Rindo’s arms and treads. She glanced at Danan, pointing to the center of its torso.

  No need for words. Danan kicked the destabilized Rindo to the ground, drove Helles into its torso—where the power core resided—and severed the energy system, triggering an explosion. Once Rindo fell silent, he pried off its thick plating.

  “What are you doing?” Eve asked.

  “Isn’t it obvious? I’m salvaging usable parts. There’s nothing to waste in the ruins or outside the tower. Look, the energy system’s fried, but the rest is in good shape, right?”

  Danan tossed a circuit board and a small semiconductor to Eve, chuckling quietly.

  “Scavenging a corpse? Not exactly admirable,” she said.

  “You’re one to talk. Machines aren’t people. Besides, in the lower city, murder and organ theft are everyday occurrences. What I’m doing is downright wholesome by comparison.”

  “…That place sounds like hell.”

  “…”

  “Kill or be killed. Take or be taken. In the lower city, life’s value is unequal. It’ll be something to see—your reaction when you witness the city’s misery.”

  With that, Danan sorted the salvageable parts and slung a rucksack, piled in the room’s corner, over his shoulder.