[BL] Residual Resonance

Chapter 1: The Red Gate in Sector C The mechanical click of plastic buttons echoed softly through the cramped corner of the office. Kai sat slouched in his worn leather swivel chair, his thumb sliding frantically across his phone screen. On the display, his game avatar executed a perfect three-hit combo, downing the digital monster boss with a flash of pixelated light. A bold green banner popped up: VICTORY! Kai let out a small sigh of relief, resting his head back against the cushion. He checked the clock in the top corner of his screen. It was 10:15 AM. To everyone else, he was just a regular twenty-two-year-old guy wasting time on mobile games at work. He wore an oversized gray hoodie, faded jeans, and cheap sneakers. He looked quiet, harmless, and completely unexceptional. And that was exactly how he wanted it. No one in this building knew that three years ago, Kai didn't even have a real name. He had only been known as Subject 07, a living experiment created in a dark, secret laboratory buried deep underground. When a combined raid by the Government and the Federation breached the facility, Kai took advantage of the absolute chaos inside the underground lab to slip away and escape into the city. Since then, he had worked hard to learn how normal people lived. He studied the rules of society, figured out how Sentinels and Guides functioned in the world, and eventually landed a quiet job where no one asked too many questions. He worked for Aether Sweep Guild. Despite the fancy name, Aether Sweep was not an elite group of heroic Sentinels fighting dangerous monsters. They were a third-tier cleaning guild. Their job was simple: after the high-ranking raid teams finished killing the monsters inside a gate, the cleaning crew stepped in to harvest valuable monster parts, collect leftover mana stones, and sanitize the area before the dungeon collapsed. It was messy, hard physical labor, but it paid enough for rent, and more importantly, it kept Kai completely invisible. The glass door at the front of the office suddenly swung open with a heavy thud. "Alright, everyone, wrap up whatever you're doing!" a deep voice boomed across the room. Boss Hank, the president of Aether Sweep, walked in wiping sweat from his forehead. He was a broad-shouldered man in his late forties with a scruffy beard and a loud, jovial personality. Behind him were three other members of the cleaning crew: Luka, an energetic guy around Kai's age, and Mr. Park, an older veteran cleaner who always smelled faintly of tobacco and antiseptic spray. Boss Hank walked straight toward Kai’s desk. He slammed a heavy manila folder packed with printed documents right onto the wood, knocking Kai’s half-empty cup of iced coffee an inch to the side. "Still playing that screen game, Kai?" Hank chuckled, leaning over the desk. "Put it away. We just landed a big job, and we need to head out in twenty minutes." Kai quickly closed his game app and locked his phone, pulling the manila folder toward himself. "A big job? I thought all Sector C gates were on hold for the week?" "They were, until two hours ago," Hank said, pulling up a folding chair and sitting down with a heavy groan. "The previous raid team that went into that Red Gate in Sector C failed miserably. Because of their failed attempt, the dungeon's stampede timer dropped drastically. The hold got lifted because if someone doesn't reset the countdown right now, a full-blown monster stampede is going to spill out into the city." Luka, who was busy tossing protective boots into a gear bag near the entrance, stopped in his tracks and whistled. "A Red Gate? Man, those are brutal." "Yeah, Calamity Class," Hank nodded solemnly. "The report says there are at least three different boss-level monsters inside. Since the last team failed, the Federation had to deploy three major combat guilds simultaneously just to breach the interior, kill the bosses, and reset the stampede countdown before the portal ruptures." Kai opened the folder and flipped through the printed pages. High-resolution satellite images showed a giant, ominous tear in space hovering over an empty factory yard, glowing with a deep, blood-red light. In this world, dungeons were categorized by color. The color of the portal told everyone exactly how dangerous the gate was before anyone stepped inside. The standard threat levels were easy to remember: Green Colored Dungeons (Minor Class): The lowest and safest rank. These usually contained small, weak monsters like goblins or slime variants. High school trainees and low-rank Sentinels used these for basic practice. Yellow Colored Dungeons (Caution Class): Moderate difficulty. Monsters here were larger and worked in organized packs. A well-coordinated team of C-Rank Sentinels was usually required to clear them safely. Orange Colored Dungeons (Hazard Class): High danger. These dungeons featured complex environments, environmental hazards, and intelligent beasts. B-Rank raid teams handled these. Red Colored Dungeons (Calamity Class): Extremely dangerous. They contained multiple boss-level entities and high concentrations of toxic monster aura. Only elite S-Rank and A-Rank guilds were authorized to enter Red Gates to prevent city-destroying stampedes. Black Colored Dungeons (Catastrophe Class): The absolute worst-case scenario. A Black Gate represented a potential world-ending event. When a Black Gate appeared, entire national armies and every available top-tier Sentinel in the region were called to action. Besides these standard combat ranks, there were also three rare, special-class dungeons that functioned completely differently: Purple Colored Dungeons (Disaster Class): These were unpredictable anomaly gates. Unlike normal gates that sat quietly until cleared, a Purple Gate had no time limit. Once it appeared, it actively leaked its internal world into reality. If a Purple Gate was a frozen tundra, the surrounding city neighborhood would literally freeze over into ice until the core was destroyed. White Colored Dungeons (Specialized Class): These contained zero monsters. Instead, they were massive, ancient labyrinths filled with deadly physical traps and environmental puzzles. Once a trap was triggered and solved, it remained inactive permanently. Because they contained rare chests filled with high-grade weapons and armor, the Federation kept White Gates strictly locked down, using them as official training grounds for newly awakened Sentinels and Guides. Blue Colored Dungeons (Mineral Class): These gates were non-combat resource sites filled with alien ores and energy-dense minerals that didn't exist anywhere else on Earth. Scientists and research institutes paid billions for access to Blue Gates to develop new medical tech and equipment to support Sentinels. "Since three big guilds are clearing this Red Gate together, the battlefield inside is going to be a complete mess," Hank explained, tapping his finger on the file Kai was reading. "Monster carcasses, shattered equipment, spilled toxic blood, and residual miasma everywhere. The official raid team expects to kill the main boss within the hour. As soon as the green light is given, our team gets first access to clean up Sector 4 of the dungeon floor." "What about the pay?" Luka called out, zipping up his duffel bag. "Triple our usual rate," Hank replied with a wide grin. "Which means if we work fast and don't slack off, everyone gets a nice bonus this month." "Triple pay sounds great," Kai said, keeping his voice calm and even while looking at the thermal scan of the gate inside the file. On the surface, Kai looked like a regular cleaner excited about extra money. But inside, his pulse quickened slightly. A Red Gate meant heavy monster miasma, a thick, toxic energy that built up in the air whenever high-ranking monsters were slain. For ordinary humans and low-rank workers, breathing in miasma without heavy specialized suits could cause severe organ failure or mental breakdown. For Sentinels, high levels of miasma accelerated their sensory overload, driving them toward madness if a Guide wasn't nearby to cleanse them. But for Kai? Kai's eyes flickered down to the palms of his hands. His body was different. The experiments forced upon him in the laboratory had altered his fundamental Guide aura. Where normal Guides could only build mental shields or soothe a Sentinel's mind through direct contact, Kai’s body acted like a black hole for corrupted energy. He could absorb, break down, and completely purify toxic miasma without feeling any pain at all. During their regular cleaning jobs, Kai secretly used this ability to quietly suck up lingering pockets of toxic air whenever his co-workers weren't looking, keeping Hank and Luka safe from miasma sickness without them ever knowing why their team had the best safety record in the city. However, a Red Gate was a completely different beast. An S-Rank battle site meant the concentration of miasma inside would be suffocatingly thick. He would have to be extra careful not to draw attention to himself. If anyone noticed that a mere third-tier cleaner was standing unaffected in the middle of an S-Rank miasma zone, his secret would be blown wide open. "Hey, Kai! Stop staring into space!" Hank clapped his hands together, standing up from the chair. "Grab your yellow hazard suit and load the suction gear into the back of the van. We leave in ten!" "Got it, Boss," Kai replied smoothly. He closed the file, stood up from his desk, and tossed his phone into his hoodie pocket. Putting on his casual, quiet smile, Kai walked toward the supply room to grab his heavy cleaning gear. It was just another day at work. Or at least, that was what he hoped it would be.