The warehouse district smelled like rust and forgotten industry, which Yuuto decided was marginally better than the wet stone of the Verdant Catacombs but significantly worse than fresh air and reasonable life choices. He stood at the edge of Sector 7, where the city's older buildings hunched against each other like tired workers at the end of a shift, and tried to remember if he'd ever dealt with an unstable dungeon core inside a populated area.
The answer was yes, twice, and both times had involved significantly more property damage than the Guild Council would have preferred.
Aria appeared first, her staff already crackling with residual flame magic that made the evening shadows dance in ways that probably violated several fire safety regulations. She'd changed into what Yuuto was beginning to recognize as her "serious dungeon crawling" outfit, which meant leather armor that actually looked functional rather than decorative and boots that could handle running through debris.
"You're sure about this?" she asked without preamble. "The Guild hasn't issued any warnings about unstable cores. If we're wrong, we're going to look like idiots breaking into a warehouse for no reason."
"I'm sure," Yuuto said, which was technically accurate if you ignored the part where his certainty came from a system notification that nobody else could see. "The mana signature is wrong. Too concentrated, too unstable. Give it another day and this entire district is going to have a monster outbreak that makes the Verdant Guardian look like a training exercise."
Lyria arrived next, moving with that same quiet grace that suggested she was far more dangerous than her healer's robes implied. She'd brought her medical bag again, because apparently she'd decided that Yuuto's tendency to solve problems in unconventional ways meant someone needed to be prepared for collateral damage.
"I can feel it," she said, her eyes going slightly unfocused in the way that suggested she was reading the ambient mana. "There's a pressure building. Like a dam about to burst, except the water is replaced by concentrated magical energy that wants to manifest as hostile entities."
"That's a deeply unsettling metaphor," Aria muttered.
"It's an accurate one. The core is trying to stabilize itself by spawning monsters, but it's inside a building with nowhere for the excess energy to dissipate. When it reaches critical mass, the entire structure is going to become a dungeon entrance, and everything within a three-block radius will be considered part of the spawning zone."
Yuuto felt a flicker of professional pride. Lyria's analysis was spot-on, and she'd reached that conclusion through pure mana sensitivity rather than system notifications. The Academy might teach suboptimal circulation patterns, but they clearly weren't completely incompetent when it came to magical theory.
Kael was last, which was becoming a pattern. He moved like someone who'd learned to conserve energy for when it actually mattered, his sword strapped across his back in a way that suggested he could draw it faster than most people could blink. The training ground session had apparently convinced him that Yuuto's crazy plans had a better success rate than conventional wisdom would suggest.
"So what's the play?" he asked, getting straight to the point in a way that Yuuto appreciated. "We can't just walk in through the front door. If there's already a core forming, there will be guardian constructs. Probably Rank D at minimum, possibly higher depending on how long it's been growing."
Yuuto pulled up his mental map of the area, cross-referencing it with the mana signature he'd been tracking since the system notification had appeared. The core was in the basement of an old textile factory, three stories of abandoned machinery and structural decay that the city had probably been planning to demolish for years.
"We go in through the loading dock on the east side," he said, already walking in that direction. "The mana concentration is lowest there, which means fewer constructs. We make our way down to the basement, I stabilize the core before it reaches critical mass, and we all go home without the city experiencing a catastrophic monster outbreak. Simple."
"Nothing about that sounds simple," Aria said, but she was already following him, her staff held ready in a way that suggested she was preparing for the plan to go sideways at any moment.
The loading dock door was locked, which was barely an inconvenience when you had a fire mage who could superheat the metal until the mechanism gave up. Aria's precision with the spell was impressive, melting just enough of the lock to make it useless without setting the entire door frame on fire.
Inside, the factory was exactly as depressing as Yuuto had expected. Rows of silent machinery covered in dust and rust, broken windows letting in the fading evening light, and the kind of oppressive atmosphere that came from a place that had been abandoned by hope and progress in equal measure.
The mana signature was stronger here, a pressure against Yuuto's senses that felt like static electricity before a thunderstorm. He could see the others feeling it too, their movements becoming more cautious as they descended the stairs toward the basement.
Lyria's hand went to her staff, her expression shifting from clinical assessment to something that looked almost eager. "There are constructs ahead. Three of them, Rank D. They're guarding the stairwell."
"Can you tell what type?" Kael asked, his hand already moving to his sword hilt.
"Mana constructs. Pure energy given form by the unstable core. They'll be fast, aggressive, and completely immune to physical damage unless you can disrupt their cohesion."
Yuuto felt the tactical analysis click into place, the same way it had with the slimes in the Verdant Catacombs. Mana constructs were annoying because they required either overwhelming magical firepower or very precise disruption of their energy matrices. Aria could probably burn through them with enough time, but time was exactly what they didn't have.
"I have an idea," he said, which was apparently becoming his catchphrase for situations where the conventional solution was inadequate. "Aria, I need you to cast your strongest fire spell, but don't release it yet. Just build up the mana and hold it ready."
She shot him a look that suggested she was reconsidering the whole "trusting the Archmage" thing, but she raised her staff and began channeling. The air around her started to shimmer with heat, flames coalescing into a sphere that grew larger and more unstable with each passing second.
"Lyria, I need a barrier spell. The strongest one you can cast, centered on Aria."
"That's going to drain most of my reserves."
"Trust me."
The barrier formed, a translucent dome of protective magic that enclosed Aria and her increasingly volatile fire spell. Yuuto could see the confusion on both their faces, the calculation of what he was planning and why it made no sense according to conventional magical theory.
Then he pulled on his EX Skill, Strongest of History, and felt the familiar sensation of the system trying to classify something it had never seen before.
Barrier plus Fire Spell. Containment plus Destruction. The fusion happened in the space between heartbeats, the two spells merging into something that made the ambient mana scream in protest.
[Skill Fusion Complete: Barrier + Fire Sphere = Compression Detonation (Rank A)]
Yuuto raised his hand and released the fused spell down the stairwell. The barrier compressed Aria's fire spell into a point of intense heat and pressure, then released it in a controlled explosion that turned the three mana constructs into dissipating energy without damaging the structural integrity of the building.
The silence that followed was broken only by the faint hum of residual magic fading into the air.
"What the hell was that?" Aria's voice had gone very quiet, the kind of quiet that suggested she was recalculating everything she thought she knew about magic.
"Compression Detonation. I fused your fire spell with Lyria's barrier to create a contained explosion that only affected the constructs. The barrier kept the blast from spreading, and the fire spell provided the destructive force. Basic fusion theory, just applied in a slightly unconventional way."
"Slightly unconventional," Kael repeated flatly. "You just created a Rank A spell on the fly from two Rank C spells. That's not unconventional. That's impossible."
"It's only impossible if you think the system's classifications are absolute. They're not. They're guidelines, and guidelines can be bent if you understand the underlying framework."
Lyria was staring at him with that same intense curiosity from the training ground, her analytical mind clearly trying to reverse-engineer what he'd just done. "You're not just fusing the spells. You're rewriting their fundamental properties to make them compatible. That requires an understanding of magical theory that goes beyond anything the Academy teaches."
"The Academy teaches you to stay within the lines," Yuuto said, already moving down the now-cleared stairwell. "I'm teaching you that the lines are optional."
The basement was worse than the factory floor above it. The mana concentration here was thick enough to make the air feel syrupy, and the dungeon core sat in the center of the room like a malignant tumor, pulsing with unstable energy that made Yuuto's teeth ache.
It was roughly the size of a human head, crystalline and wrong, with fractures running through it that leaked raw mana into the surrounding space. The system had been right about the timeline. Another twelve hours, maybe less, and this thing would have gone critical.
"Stay back," Yuuto said, approaching the core slowly. "If this goes wrong, you'll want to be as far away as possible."
"What are you going to do?" Aria asked, though she was already backing toward the stairs.
"Stabilize it. The core is trying to spawn monsters because it has too much energy and nowhere to put it. I'm going to give it somewhere to put it."
He placed his hands on the core's surface, ignoring the way the unstable mana tried to reject his touch, and pulled on his EX Skill again. This time, he wasn't fusing spells. He was doing something far more dangerous and far more necessary.
He was hacking the dungeon core's fundamental programming.
The system that governed dungeons was old, older than the current Guild structure, older than most of the kingdoms that dotted the continent. It operated on rules that had been set by the original creators, whoever they were, and those rules had never been meant to account for someone like Yuuto who could see the underlying code and rewrite it on the fly.
The core's energy matrix was a mess, fractured and unstable, trying to execute commands that contradicted each other. Spawn monsters. Maintain structural integrity. Expand the dungeon. Contain the expansion. It was caught in a logical loop that could only end in catastrophic failure.
Yuuto rewrote the loop.
Instead of spawning monsters, the core would vent excess energy into the ambient mana field, dispersing it harmlessly over time. Instead of trying to expand, it would enter a dormant state, waiting for proper conditions that would never come. Instead of maintaining a dungeon entrance, it would simply exist as a stable mana source, useful for nothing except maybe powering a few enchantments if someone bothered to harvest it properly.
The fractures in the core began to seal, the pulsing energy stabilizing into a steady, harmless glow. The pressure in the room dropped, the oppressive atmosphere fading into something almost peaceful.
Yuuto stepped back, feeling the drain on his mana reserves that came from doing something the system had never been designed to allow. His status screen chimed, a notification appearing in his peripheral vision.
[Skill Unlocked: Core Stabilization (Rank EX)]
[Effect: Allows direct manipulation of dungeon core programming. Can stabilize, modify, or destroy cores without combat. Growth rate: Infinite]
[Achievement Unlocked: First Core Stabilization]
[Reward: Skill Fusion Slot Unlocked - Can now maintain three active fused skills simultaneously]
[Party Bonus Applied: All party members receive +10% to primary stat growth for 24 hours]
Yuuto turned to find his party staring at him with expressions that ranged from awe to something that looked like existential crisis. Aria's staff had gone dark, the flames extinguished as if she'd forgotten she was holding it. Lyria's analytical mask had cracked completely, replaced by naked fascination. Kael just looked tired, like he'd accepted that his new party leader was going to keep doing impossible things and he might as well get used to it.
"The core is stable," Yuuto said, which felt like an inadequate summary of what had just happened but was technically accurate. "The city is safe. No monster outbreak, no catastrophic mana surge, no need for the Guild to mobilize a full response team."
"You just rewrote a dungeon core," Lyria said, her voice barely above a whisper. "That's not a spell. That's not even advanced magic. That's system manipulation on a level that shouldn't be possible."
"It's possible if you understand how the system works. Dungeon cores are just crystallized mana with a set of instructions encoded into their structure. If you can read those instructions, you can change them. It's not that different from optimizing circulation patterns, just on a larger scale."
"Not that different," Aria repeated, her voice climbing toward something that might have been hysteria or laughter or both. "You're comparing rewriting the fundamental programming of a dungeon to fixing someone's mana efficiency. Do you have any idea how insane that sounds?"
"I'm aware it's unconventional."
"Unconventional. Right. That's the word we're using."
Kael cleared his throat, drawing their attention. "We should probably leave before someone notices we broke into a condemned building and tampered with a dungeon core. Even if we prevented a disaster, the paperwork is going to be a nightmare."
He had a point. Yuuto could already imagine the Guild's reaction when they found out about this. Questions about how he'd known the core was unstable. Questions about his methods. Questions about why he hadn't reported it through proper channels instead of handling it himself with a party of relatively inexperienced adventurers.
They made their way back through the factory, the oppressive atmosphere gone now that the core had been neutralized. The evening had faded into full night while they'd been underground, and the warehouse district was quiet except for the distant sounds of the city going about its business.
"So," Aria said once they were safely outside and the loading dock door had been secured behind them. "What now? Do we report this to the Guild? Do we pretend it never happened? Do we all agree to never speak of the fact that our party leader can apparently hack reality?"
"We report it," Yuuto said, pulling out the temporary Guild card the registration clerk had given him. "But we keep the details vague. We detected an unstable core, we neutralized it before it became a threat, and we're filing a formal report so the Guild can send someone to harvest it properly."
"And when they ask how we neutralized it?"
"We tell them I used a specialized stabilization technique from my previous training. Which is technically true, just missing a few details about what that training actually involved."
Lyria was still staring at him with that intense curiosity, and Yuuto recognized the look. She was going to have questions. Lots of questions. Probably an entire notebook full of questions by the time they made it back to the Guild Hall.
"The system notification said we got a party bonus," she said, confirming his suspicion that she'd been paying attention to more than just the core stabilization. "Plus ten percent to primary stat growth for twenty-four hours. That's going to stack with the optimization training from earlier. We could make significant progress if we spent tomorrow doing focused skill development."
"You want to spend your bonus time grinding?" Aria asked, incredulous.
"I want to take advantage of every opportunity for improvement. The MC just showed us that the ceiling for magical growth is far higher than anyone currently believes. If we're going to keep up, we need to push ourselves harder than we ever have before."
Kael nodded slowly, his hand resting on his sword hilt in what Yuuto was beginning to recognize as a thinking gesture. "She's right. We just participated in preventing a city-wide disaster, and we did it with a party leader who can casually perform feats of magic that violate everything we were taught was possible. If we want to be useful instead of just along for the ride, we need to get stronger."
Yuuto felt something warm settle in his chest, a sensation that took him a moment to identify as pride. They were taking this seriously. Not just the immediate crisis, but the larger implications of what he was teaching them. They wanted to grow, to push past the limitations the current system had imposed on them.
"Tomorrow," he said, making the decision as he spoke. "We'll spend the day at Kael's training ground. No dungeons, no distractions. Just focused skill development and optimization work. I'll teach you the next level of circulation refinement, and we'll work on identifying your individual specializations."
"Individual specializations?" Aria raised an eyebrow.
"The Academy teaches everyone the same way because it's efficient and safe. But you're not everyone. Each of you has natural affinities and tendencies that are being suppressed by trying to fit into the standard mold. Tomorrow, we're going to figure out what those are and start building your skillsets around them instead of against them."
The Guild Hall was still open when they arrived, though the crowd had thinned to just a few late-night adventurers and the clerk who'd registered Yuuto earlier. She looked up from her ledger with an expression that suggested she'd been hoping for a quiet evening and was disappointed to see them.
"You're back," she said, her tone carefully neutral. "I'm going to assume this isn't a social visit."
"We need to file a report," Yuuto said, setting his temporary card on the counter. "Unstable dungeon core in Sector 7, old textile factory. We neutralized it before it reached critical mass. The Guild should send a recovery team to harvest it properly."
The clerk's expression shifted from neutral to alarmed in the space of a heartbeat. "An unstable core? Inside the city? How did you even know it was there? Our detection systems should have flagged it days ago."
"Your detection systems are optimized for cores that have already manifested as dungeon entrances," Yuuto said, which was true and also a polite way of saying the Guild's monitoring infrastructure was inadequate. "This one was still in the formation stage. I detected it through specialized sensing techniques."
"Specialized sensing techniques," the clerk repeated, her hand already moving toward the communication crystal. "And you neutralized it how, exactly?"
"Mana stabilization. I interrupted the core's spawning cycle and put it into a dormant state. It's no longer a threat, but it should be harvested soon before it starts accumulating energy again."
The clerk activated the crystal, speaking in rapid, clipped sentences to whoever was on the other end. Yuuto caught fragments of the conversation, enough to know that this was going to escalate quickly. Unstable cores inside populated areas were the kind of thing that made Guild officials panic, and the fact that a party of relatively unknown adventurers had handled it without official oversight was going to raise questions.
"The Council wants to see you," the clerk said after ending the communication. "All of you. Tomorrow morning, first thing. They're sending a team to verify the core's status tonight, and depending on what they find, you're either going to be commended or investigated."
"Probably both," Kael muttered.
The clerk didn't disagree.
They left the Guild Hall with a formal appointment card and a growing sense that their lives were about to get significantly more complicated. Yuuto had known this would happen eventually. You couldn't prevent a major disaster and expect to fly under the radar. But he'd been hoping for a few more days before the political machinery started grinding.
"So," Aria said once they were back on the street. "Guild Council meeting tomorrow morning. Training session tomorrow afternoon, assuming we're not arrested for unauthorized dungeon core manipulation. Anything else we should add to the schedule?"
"Sleep," Lyria suggested. "And possibly some time to process the fact that we just prevented a catastrophe that would have killed hundreds of people."
"Sleep is overrated," Aria said, but her voice lacked its usual energy. The adrenaline was wearing off, leaving behind exhaustion and the kind of bone-deep weariness that came from surviving something that should have been far more dangerous than it was.
Yuuto watched them disperse, Aria and Lyria heading toward their inn, Kael toward his family's estate. The city was quiet around him, completely unaware of how close it had come to disaster. Tomorrow would bring questions and complications and probably more attention than he wanted. But tonight, standing in the empty street with the weight of a successful crisis prevention settling into his bones, Yuuto allowed himself a moment of satisfaction.
He'd come back to a world that had forgotten him, to a Guild that no longer existed and friends who were long dead. But maybe that didn't have to be the end of the story. Maybe it could be a beginning instead.
His status screen chimed softly, a final notification appearing in his peripheral vision.
[Quest Updated: Rebuild the Guild]
[Progress: First Crisis Resolved]
[New Objective: Establish Party Reputation]
[Reward: Unknown]
[Warning: Political Attention Increased]
[New Quest Available: Navigate the Council]
[Objective: Survive tomorrow's meeting without revealing your true level]
[Reward: Maintained Cover Identity]
[Failure Consequence: Immediate political complications]
Yuuto smiled. The system was adapting to his situation, recognizing that he wasn't just trying to become stronger but to build something larger than himself. The Age of Heroes might be over, but apparently someone had forgotten to tell the dungeon cores.
And maybe that was okay. Maybe the world needed someone who remembered when magic had been more than just following safe, predictable patterns. Maybe it needed someone who could look at an unstable core and see not a disaster but a problem with a solution.
Maybe it needed someone who was willing to break the rules to save the people who didn't even know they were in danger.