RUMBLE—!!!
Beneath the thunderous roar of a waterfall, two figures dropped in utter disarray, crashing into the enormous lake on Dungeon Floor 25.
The crushing water pressure swallowed everything at once—
cold, darkness, and the suffocating force that felt like it would crush lungs flat.
"Glrk…"
Shirou Emiya lost consciousness the instant he hit the water. The Broken Phantasm had nearly drained the last shred of his mental strength, and on top of that, the internal injuries from taking a Level 5 hit head-on left him like a true piece of scrap iron sinking to the bottom.
"E-Emiya-sama!"
Liliruca Arde (Lili) thrashed her limbs desperately, moving like a tiny mermaid whose combat power had suddenly spiked to the ceiling (even though she was a prum). She clung to Shirou's collar with a death grip, using the buoyancy of her new gear—the Lightweight Pack—to fight her way toward the shore.
"Don't die… you can't die here—absolutely not!"
This was Floor 25 — the Great Falls, the labyrinthine "Water City," a paradise of caves and torrents… and also a cafeteria for aquatic monsters.
"—HSSS!"
Before they could reach land, a spine-chilling slicing sound came from below the surface.
Several blue dorsal fins cut through the water—signals that Killer Fish and Raiga were closing in.
They'd smelled blood, and the excitement hit them like a shopping addict spotting a massive sale banner.
"Damn it—get away!"
With one arm dragging Shirou, Lili forced her other hand up, raised her hand crossbow, and fired blindly at the rippling surface.
Thwip!
The bolt vanished into the lake, blossoming a tiny flower of blood.
It didn't scare them off.
It only excited them.
"I'm… done…"
Lili stared at the widening ripples surrounding them and felt despair crawl up her spine.
Shirou was unconscious. Her stamina was nearly gone. The monsters around them were all Level 2 threats.
This was checkmate.
So this was the ending for a side character without plot armor?
Just as a massive Raiga opened its jaws to enjoy this "drowning delivery meal"—
"La… La… La…"
A clear, ethereal song suddenly echoed through the cavern.
No lyrics—only a pure melody.
It pierced the waterfall's roar, cut through the spray and the surface of the lake, and rang directly inside the minds of every living thing present.
A miracle happened.
The frenzied monsters froze mid-motion.
The red light in their eyes faded, replaced by a dreamy calm—as if a raging beast had abruptly had its "berserk mode" switched off.
"Glrk…"
The Raiga closed its mouth, even blew a bubble in a strangely human way, then flicked its tail and slipped back into deeper water.
The other monsters dispersed as well, as though the murderous intent from moments ago had been a shared hallucination.
"W-What is…?"
Stunned, Lili seized the chance.
Burning the last of her strength, she finally hauled Shirou up onto a dry rock shelf at the shore.
"Cough—! Cough, cough!"
She gulped air, then forced herself to look toward where the song had come from.
Through the mist thrown up by the falls—
On a reef jutting above the water sat a beautiful being.
Long sea-blue hair.
Skin pale enough to look translucent.
And instead of legs, a long tail covered in blue scales.
A Mermaid.
A monster said in legend to lure sailors to their deaths with song.
"M-Monster…"
Lili tightened her grip on her dagger, trembling.
First escaping the tiger's den (Dix), only to fall into a wolf's mouth (a mermaid)?
And the presence she gave off… this wasn't a harmless "singing decoration." This was an upper-tier monster.
But—
The mermaid didn't attack.
She stopped singing and stared at them with large, pure eyes like sapphires—curious, not hostile.
Then she did something that shattered Lili's worldview.
She slipped off the reef, used her tail to glide smoothly across the shallows, and came up right in front of Lili.
She pointed at Shirou.
Then pointed at herself.
Then tilted her head.
"That… is the one who saved Wiene… our benefactor?"
A bright, clear voice—speaking clumsy human common tongue.
"…Huh?!"
Lili's jaw practically hit the rock.
"Y-You can talk?!"
Again?!
First a dragon girl, now a mermaid?
What was wrong with this Dungeon—had the version update jumped straight to "everyone becomes monster girls"?!
"I am… Marie."
The mermaid tapped her chest and smiled with innocent openness.
"Fels said… a red-haired good person… fell down."
So there really was an "insider" waiting to receive them.
Lili's tension finally loosened.
That skeleton-man Fels looked like a final boss, but apparently he handled things like someone reliable.
"Please—save Emiya-sama!"
Lili grabbed at hope like a lifeline.
"He's badly hurt! His bones are broken, and he was poisoned—"
"Hurt?"
Marie leaned close to Shirou, nostrils flaring slightly.
"…Mm. Strong blood smell."
Her beautiful brows knit as she thought.
After a brief pause, as if deciding something important, she extended her slender wrist toward Shirou's mouth.
"Here."
"Huh?"
Lili blinked in confusion.
"My blood… is medicine."
Marie used a sharp fingernail to slice her wrist. Blue-red blood welled up and flowed.
"Drink… and get better."
So this was the "mermaid flesh" myth variant—except in blood form.
In Dungeon stories, mermaid flesh and blood were said to have miraculous healing power. Which was also exactly why mermaids were among the most coveted targets for poachers.
Lili didn't hesitate.
She lifted Shirou and helped him swallow the precious blood.
Gulp.
The moment it slid down his throat—
The wounds deep enough to expose bone began to close at visible speed.
His deathly pale complexion warmed, returning to color.
His faint breathing steadied and grew stronger.
Xenos vitality… was basically a walking full restore potion.
"Ugh…"
A few minutes later, Shirou's eyes slowly opened.
The blurry world sharpened.
The first thing he saw was Lili's face streaked with tears—
and another face leaning in close, breathtakingly beautiful… just not entirely human.
"She woke him!"
Marie clapped happily, her tail making light slap-slap sounds against the ground.
"You are…"
Shirou pushed himself up. Aside from lingering weakness, most of the pain had dulled dramatically.
His Mind's Eye told him the mermaid carried no malice.
"I am Marie!"
She beamed.
"Wiene's friend! You… Shirou?"
"You know me?"
Shirou froze, then gave a weary smile.
"…Looks like I'm famous in your circle."
"Mm! Everyone knows!"
Marie nodded hard.
"You are… the 'fool' who hugged monsters."
"'Fool,' huh…"
Shirou rubbed his nose.
"…Yeah. That's a pretty accurate title."
"Emiya-sama! Thank goodness—thank goodness you woke up!"
Lili threw herself into him again, sobbing uncontrollably.
"Lili thought… Lili thought she'd never see you again…"
"Sorry. I scared you."
Shirou patted her head gently, but his gaze swept the surroundings.
Floor 25—the Water City.
They'd escaped immediate death, but this was still deep territory.
"Marie."
Shirou turned to the mermaid.
"Do you know anywhere safe we can rest? We need time to recover mana."
"I know!"
Marie pointed behind the waterfall.
"There… our secret base. Fels also there."
"Fels is there too?"
Shirou's eyes narrowed.
So this wasn't just coincidence.
It was an arranged meeting.
"Lead the way."
He rose. His body still swayed, but the resolve in his eyes had returned.
"And honestly… I've got an account to settle with that skeleton gentleman."
(Primarily for the part where he "threw me down here.")
…
Meanwhile—
On Floor 24, at the edge of the blasted-out hollow tree cavern—
Several robed figures in black appeared.
They stared at the enormous crater and the terrifying residual mana trace, falling into silence.
"This is… the power of 'Unlimited'?"
One of them whispered, voice trembling.
"That level of destruction… can a Level 2 really do this?"
"Dix, that idiot, actually provoked a monster like that."
Another snorted.
"But it proves the boy's value. If we capture him and turn him into a 'key'… or use him as bait for the Xenos…"
"Don't be careless."
The leader—a tall masked woman, clearly a high-ranking member of the dark faction—spoke coldly.
"He isn't dead. He fell to Floor 25."
"And according to our information… the Xenos have already made contact."
"Pass the order."
A cruel gleam flashed in her eyes.
"Activate the artificial labyrinth's backup entrance."
"Seal every route from Floor 25 to Floor 18."
"This time, we're not capturing."
"We're hunting."
"If he can't be used—then let him drown in the water labyrinth… together with the monsters."
....
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