Location: Floor 1.5 - The Undercity Sewers
(Between Layers of Aincrad)
The smell hit them first. It wasn't just sewage. It was Mana-Enriched Sewage. It smelled like sulfur, expired potions, and the regrets of a thousand gacha players who didn't pull the SSR unit.
"My suit!" Reigen Arataka gagged, brushing green slime off his cheap gray lapel. "This is a dry-clean only fabric! Do you know how hard it is to get ectoplasm stains out?!"
Kazuma splashed through the knee-deep muck, holding his nose.
"Quiet, Con-Man. Look around."
The sewer tunnel was colossal. Pipes the size of subway trains crisscrossed above them, leaking neon fluid. Red eyes blinked in the darkness. Hundreds of them.
Goblin Slayer stepped forward. He kicked a skull into the water.
"They're coming," he said.
"Goblins?" Tanjiro sniffed the air, hand on his sword. "It smells like... fur. And wet dog. And... ramen?"
From the shadows, a shuriken the size of a pizza pan flew out.
Clang.
Goblin Slayer parried it with his buckler.
"Not Goblins," the Slayer muttered. "Long Goblins."
"DIE-DIE, MAN-THINGS!"
A horde of hunched figures splashed into the light. They were Skaven (rat-men from Warhammer). But they weren't wearing rags.
They wore orange jumpsuits. And leaf headbands.
"They're Ninja Rats!" Usopp shrieked, hiding behind King.
A Skaven Warlock-Engineer stepped forward, forming a ball of chaotic green energy in his claws.
"Chakra-Chakra! Yes-Yes! Warp-Fire Rasengan!"
"That's copyright infringement!" Kazuma yelled.
The Rat lunged.
Scene: The Battle of the Filth
"Water Breathing: Second Form - Water Wheel!"
Tanjiro leaped, spinning vertically. His blade slashed through the Warp-Rasengan, dispersing the green energy.
"Please!" Tanjiro pleaded, landing gracefully in the sludge. "We don't want to hurt you! We just fell down a hole!"
"Kill-stab the nice one!" the Skaven cheered.
"Tanjiro-kun! Kindness doesn't work on vermin!" Shinobu Kocho (Insect Hashira) fluttered down from a pipe, landing lightly on the surface tension of the sewage water.
"Insects and rodents... natural enemies. Insect Breathing: Dance of the Centipede."
She moved faster than sight, zig-zagging through the horde. Sting. Sting. Sting.
Wisteria poison injected. The rats convulsed and started foaming purple bubbles.
"Are they dead?" Usopp peeked out.
"Paralyzed," Shinobu smiled pleasantly. "It will take about forty minutes for their organs to liquefy. Shall we have tea while we wait?"
"Scary!" Everyone shouted.
"More come!" Goblin Slayer pointed his short sword down the tunnel.
Shadow Clones.
The surviving Skaven made hand signs.
Poof. Poof. Poof.
Thousands of Rats filled the tunnel, wall to wall. A tsunami of fur and daggers.
"There's too many!" Reigen panicked. "King! Do the thing! Use your Conqueror's Haki!"
King stood frozen. His shoes were soaked. He was thinking about how much bacteria was currently entering his socks.
DOKI DOKI DOKI.
The reverberation shook the loose bricks in the ceiling.
The Skaven front line skidded to a halt. Their whiskers twitched.
"Squeak-fear! The Tall-Man! He vibrates with murder-intent!"
"Wait," Kazuma analyzed the situation. "These aren't smart rats. They're Skaven. They're cowardly backstabbers."
Kazuma smirked. He activated his ultimate weapon: Dishonesty.
"Halt!" Kazuma stepped forward, mimicking King's menacing silence. "I am the Rat King! Can't you see the aura? If you attack, I will release the Cats!"
"CATS?!" The horde rippled with panic. "THE GIANT MEOW-MEOWS?"
"Yes," Kazuma lied. "Thousands of them. In my pocket. Do you want to see?"
The Rats looked at Kazuma. Then at King (who looked like he was about to explode).
"Run-flee! Better to fight the Turtle-things in Zone B!"
The entire horde vanished down a drainpipe in seconds.
"Success," Kazuma wiped sweat from his brow. "My Charisma stat finally paid off."
Scene: The Lost Swordsman
While the main group navigated the sewers, Roronoa Zoro was facing a different problem.
He had fallen down a different chute.
He stood in a green pipe. The world around him was blocky. Pixelated.
"Where is this?" Zoro muttered. He touched a floating brick. It broke and gave him a coin.
A Goomba walked toward him.
But this Goomba had the face of Dio Brando.
"It was me, Goomba!"
"Weird mushroom," Zoro drew Shusui. "It's annoying."
Slash.
He cut the Goomba-Dio. It popped.
Zoro looked left. A endless side-scrolling landscape.
Zoro looked right. A solid wall.
"Okay," Zoro nodded confidently. "The right path is clearly through the wall."
Santoryu Ogi: San Zen Se-Kai! (Three Thousand Worlds).
He spun his swords.
He didn't just cut the wall. He cut the Code.
GLITCH.
The pixel world shattered. Zoro walked through a rip in the screen background.
"Found the kitchen," Zoro noted, stepping out into a boiler room where Saitama was currently toasting a piece of bread over a steam pipe.
"Oh," Saitama looked up. "Hey, Moss-Head. Want some toast? It smells a bit like methane, but it's crunchy."
Scene: The Boss of the Beneath
Back with Kazuma's group, the path ended.
A massive, circular chamber. Sewage waterfalls cascaded from high above (the drainage from the Marketplace floor).
In the center stood a figure.
He was wrapped in tattered, blood-red bandages. He hunched over a katana that dripped with virulent green slime. He was a Rat. A huge, mutated Rat.
STAIN-TWITCH. (The Hero Killer Stain + Twitch the Plague Rat).
"Hiding in the sewers..." The Boss rasped, flicking his long, pink tail. "Like proper garbage. "I demand-ask... are you True Heroes? Or just fakes to be cull-killed?""
He disappeared. Camouflage.
"Invisible!" Tanjiro warned. "Guard your backs!"
SCHLICK.
Blood sprayed.
Goblin Slayer stumbled forward, a gash in his shoulder armor.
"Fast," Slayer grunted.
"One down!" The voice echoed from everywhere. "The fake helmet-man bleeds! Lick-lick!"
Stain-Twitch appeared, long tongue extending to lick the blood on his blade to activate his Paralyze Quirk.
"Don't let him lick it!" Deku (who just caught up) shouted. "Stain's quirk paralyzes you upon blood ingestion!"
"Fireball!" Megumin (carried by Darkness) raised her staff.
"No!" Kazuma tackled her. "Methane gas! If you explode in here, we all burn!"
"Filthy fakes!" Stain-Twitch lunged at the helpless team. "I will PURGE YOU YES-YES!"
Suddenly, a metallic clang echoed.
A drain grate on the ceiling flew off.
Falling from above was... a turtle?
No.
A Tortoise.
Master Oogway (Kung Fu Panda) fell in slow motion.
But he held a shield. Naofumi's Shield.
Wait.
It wasn't Oogway.
It was Teenage Mutant Ninja Raphtalia?
(No, that's too weird even for this fic).
It was Master Roshi inside a Gamera shell.
Fusion: Turtle Hermit Gamera.
"MAFUBA!" Roshi shouted, spinning in the air.
He wasn't trapping the Boss. He was clearing the air.
A whirlwind swept the methane away.
"Now!" Kazuma yelled. "The gas is gone! EXPLOSION GIRL, DO IT!"
Megumin's eyes flashed red. She began her chant.
"Darkness beyond twilight... crimson beyond blood that flows..."
"Shoot-kill the mage!" Stain-Twitch scurried along the wall, loading a crossbow with poisoned bolts.
"No you don't!" Usopp locked on.
He pulled back Kabuto. He loaded... a Tabasco Star? No.
He loaded a "Saitama's Shiny Head Sticker" (Rare Drop from Floor 1).
"Special Attack: FLASHBANG STAR!"
He fired. The pellet hit the wet wall next to the Rat.
The sticker reflected the faint sewer light.
It wasn't bright.
But Stain-Twitch, having lived in darkness, had sensitive eyes.
"MY EYES! THE SHINY! IT BURNS!" The Boss shrieked, covering his face.
"EXPLOSIOOOOOOOON!"
Megumin unleashed the nuke.
Golden fire filled the chamber.
The sewer water flash-boiled into steam.
The Boss... vanished. Vaporized instantly.
The recoil sent Megumin flying back. Darkness caught her (and enjoyed the wall slam).
"Nice shot," Goblin Slayer muttered, clutching his wound. He threw a potion at the scorched ground.
[FLOOR 1.5 CLEARED]
[BOSS: STAIN-TWITCH DEFEATED]
[LOOT DROPPED: "HERO KILLER'S CHEESE" (Legendary Item)]
The ceiling grate opened fully. A ladder descended.
Light. Fresh air.
And the sound of... racing cars?
[WELCOME TO FLOOR 3]
[THE RAINBOW ROAD OF RAGE]
[GENRE: KART RACING]
"No," Kazuma looked up at the rainbow-colored track floating in the sky. "I don't have a driver's license!"
"I do!"
A Toyota AE86 drifted out of the sewer pipe wall (don't ask).
Takumi Fujiwara leaned out.
"Get in losers. We're going drifting."
"Shotgun!" Goku yelled, teleporting into the passenger seat.