The Royal Military Academy's Impostor Owns a Dungeon [BL]

The sound came first.

A deep, thunderous rumble rolled across the battlefield, followed by the hiss of rushing water.

Then it hit.

WOOOOOSH—!

The tide surged from the sides, sweeping over the battered terrain. It wasn’t as massive as the earlier tsunami they were saved from. Still, it carried the wreckage of everything it had touched before—splintered trees, fragments of buildings, shattered armor, scattered debris, and the torn remains of corrupted beasts dragged from the depths.

The air crackled with the sound of crashing metal, and the unending roar of water smashing through the ruins filled the air. The ground trembled beneath the weight of the flood as everyone scrambled back.

Amid the chaos, a single mecha dragged itself from the rubble. Its once-polished armor was torn and gouged, half of its frame pierced clean through by jagged claws. With what strength remained, the pilot severed the impaled limbs, sparks spraying in short, violent bursts.

”Come on... move,” the pilot muttered, voice hoarse through the static-filled comms.

The mecha’s arm reached out, trembling, scraping the ground inch by inch as the tide grew closer. The water was nearly upon him now—dark, heavy, likely carrying the stench of death.

He knew it was useless. Still, he kept reaching.

And then—something gripped his hand.

The pilot froze, breath catching in disbelief. Slowly, he turned his hazy feed toward the source, expecting teeth or claws or the shadow of another monster.

But instead—

It was a mecha.

Unfamiliar, gleaming even in the half-light, its white frame was unlike anything he’d ever seen.

The crest etched onto its armor caught the faint glint of broken light.

House Kyros.

And it wasn’t alone.

One after another, they dropped from the skies in blinding arcs—white silhouettes cutting through smoke and ruin. Some swooped low, striking clean and tearing off monsters that clung to fallen mechas.

Suddenly, pilots who had stopped believing in rescue were being lifted, pulled free from the wreckage, and carried away.

For a moment, the pilot couldn’t breathe. His chest tightened, but not from fear.

He looked up through his cracked cockpit screen as another white shadow descended before him, the House Kyros insignia blazing like fire amid the chaos.

Saved.

They were saved.

__

Somewhere deep beneath the ocean, far below the reach of sunlight and deeper still than any human had ventured in decades, two pilots were staring at the source of the tsunami they didn’t even know existed.

At first, it was quiet. Just the low hum of their damaged systems and the soft crackle of the comms.

Then—

RUMMMMBLE.

”!!!”

Both Sera and Nia instinctively braced as the ground beneath them trembled. Silt burst upward in great clouds, turning the water around them into murky chaos.

”What was that?!” Nia gasped.

Sera’s voice came out sharp and tense. ”Nia... I think it’s moving.”

Nia blinked. ”What’s moving?”

”That thing.” Sera’s tone dropped to a whisper. ”That monster—it’s moving. And it’s moving in this direction.”

”Wait, WHAT?! Are you saying it’s coming for us?!”

Sera’s voice tightened. ”I doubt it’s after us, but if my readings are right, the only thing that makes sense is that it’s heading for shore.”

”WHAT?!” Nia screamed, right as another violent quake rippled through the seabed. The rock formation they had been hiding inside began to crack and crumble.

”We have to go! Now!” Sera shouted.

Her mecha shifted, bracing itself to run, but before she could move, the ground began to lift. The sand and debris beneath them were rising—no, being pulled upward.

”What the hell—!” Nia’s panicked voice barely cut through the rumble.

The rock they were using as cover suddenly fractured, collapsing in on itself. Reflexively, Nia moved to shield Sera’s mecha, the only thing a broken manual mecha could really do in this situation, but before they were buried in underwater rubble, Sera’s own shield burst to life, forming a dome of blue light that absorbed the falling debris.

”Don’t do that again!” Sera barked. ”Your mecha can’t handle this kind of impact anymore. Mine’s still intact!”

”Oh, excuse me, Miss ’Intact Shield’!” Nia snapped back, her voice shaking. ”Shouldn’t you be the last person talking about ignoring warnings?! Who was it that followed me here, huh?”

”Now’s not the time!” Sera shot back.

The water around them distorted as more cracks split the seabed. The two pilots didn’t have time to argue—Sera grabbed Nia’s damaged mecha with her mechanical repair arms and pulled, forcing both forward through the pitch-dark depths.

Her sensors flickered, the pressure alarms whining. Still, she kept going.

”Hold on tight!” she said, gritting her teeth as she dragged them toward the faint light above.

Behind her, Nia’s trembling voice came through the comms. ”Sera... I don’t think the Empire has enough people.”

”What?”

Nia’s tone dropped, quiet but filled with dread. ”You might not want to look behind us.”

Sera, however, risked a glance over her shoulder—

—and her blood ran cold.

A shadow was moving in the distance. Vast. Enormous. It stretched so far that her sensors couldn’t register its full outline. In fact, at this point, she wasn’t even sure if the ocean had always looked like this.

Sera’s focus snapped forward again. ”Let’s just get out of here!”

But it wasn’t easy. It was as if the number of tentacles were multiplying, spreading faster, lashing out like spears. Every strike rattled the shield, making her cockpit tremble.

Sera gritted her teeth. ”Please, please, please—”

Her hands shook on the controls. The shield flickered, the impact reverberating through the mecha. Cracks began to form across its surface. While the mecha was nearly on par with known S-class mechas, this was still a B-class unit being piloted by a B-class pilot. And as a support, it likely wasn’t made for this—it shouldn’t even have lasted this long.

Red warning lights filled the cockpit.

[SPIRITUAL ENERGY CRITICAL]

[SPIRITUAL DEPLETION IMMINENT]

Her head pounded. Her breathing grew shallow. The edges of her vision were going dark.

Not yet.

They couldn’t die here.

She reached for the override switch near her leg, ready to force the system to keep running despite the alarms, when—

Whoooosh—

A soft hiss echoed inside the cockpit, followed by the sound of a small compartment opening. It was the kind of quiet vacuum sound that came when the freezer door released its seal.

Sera blinked in confusion. ”What the—?”

The alerts changed.

[EMERGENCY RATIONS DETECTED. PLEASE CONSUME BEFORE DEPLETION.]

”What?” she croaked.

Her trembling hand reached for the open compartment. Inside—

Her eyes widened.

How on Solaris did she have something like this in here the whole time?

Who knows?

But her throat tightened. Then she burst out laughing, tears falling in her relief.

Sergeant Nia, confused and panicked, shouted through the comms, ”Sera! What’s going on?! Why are you laughing right now?!”

Through tears and half-choked giggles, Sera shoved one of the rations into her mouth. ”Nothing! Nothing’s wrong! It’s just that—if we die here, I’ll be so embarrassed even in the afterlife!”

Because what she found inside that compartment wasn’t only emergency rations

It was a reminder.

A small, unspoken reminder that whoever built this mecha had done so with one thought in mind—

Everyone had to survive.

__

Achoo!

Luca sneezed so suddenly that even D-29 paused mid-sentence.

Immediately, Xavier’s voice came over the comms, calm but concerned. ”Luca, are you feeling sick?”

The golden-eyed mechanic sniffled once, blinking in surprise. ”Huh? Oh, no, I’m fine!” he smiled as if to reassure him, his voice bright and just a little too cheerful. ”Really, I feel great! Actually, better than great!”

The prince, however, wasn’t convinced. ”You’re sure?”

”Mhm!” Luca chirped, his tone suspiciously sunny. ”I was really worried earlier when I saw the devastation behind us while trying to siphon out the water, but now that I’ve seen our soldiers helping with the evacuations, I feel much better.”

He spoke with that innocent sincerity that always disarmed Xavier, even when it made him more suspicious.

Over the comms, the worried husband exhaled softly. ”I see. That’s good, then. But still, let’s have that checked later.”

Luca’s mecha turned slightly, even though no one could even see him; his eyes shone as he explained, ”Hmm, okay! But really, I feel better! How could I not, when D-29 just reported that we recovered a good amount of CP from the tsunami water!”

”...What?”

”Yes!” Luca said proudly. ”Apparently, the water was really contaminated. It wasn’t the active kind, so it didn’t look like the usual type, but still, it gave CP! Can you believe it? To think there’s still so much water left in the ocean!”

He sounded delighted. Too delighted.

Xavier pursed his lips in his cockpit. ”Luca...”

”Yes?”

”...If you’re coming to get more CP, remember to call me, okay?” Xavier sighed, convinced that even his brain had been eternally rewired, as his first thought was how they could efficiently drain the water of corruption.

After realizing that it would be best if people didn’t hear his thoughts, he just said, ”I’m just glad you’re not sick. But after all this, you’re resting before continuing with experiments.”

”Oh, okay,” Luca replied softly, his smile warm and obedient. After all, his husband always said the right things about rest, and he always felt better after following his suggestions.

For a moment, everything was peaceful—well, compared to earlier, even an explosion right now would sound like child’s play. So, the rumble of the mecha, the soft hum of power systems, and the sound of waves settling seemed peaceful.

Then D-29’s voice suddenly cut through.

”Host!” it shouted, urgent. ”There seems to be a familiar signal emerging from the water!”

”Huh?”