Kazuki Hiro wasn't special.
He was a twenty-three-year-old NEET who hadn't left his cramped apartment in almost a year. His days were a blur of instant ramen, hentai visual novels, and whatever VR fantasy MMO held his attention that week. Human interaction? He barely remembered what his parents' voices sounded like. Romance? Only in 2D.
But as it turned out, fate didn't care about how pathetic you were.
It just needed a reason.
And Kazuki's reason was as stupid as it was tragic.
"Kazuki Hiro, Level 99 Mage, you have reached the final gate of the Demon King's Citadel."
His screen blared with triumphant music. His VR suit vibrated as the magic cannon on his back charged with a satisfying hum. He grinned.
"I'm gonna solo this damn boss if it kills me," he said proudly.
It did.
More specifically, his VR full-dive rig short-circuited and fried his brain mid-battle.
He never saw the Demon King's death animation.
Darkness.
But not empty darkness. Not the peaceful, sleep-like nothingness he expected from death.
This darkness... was conscious. It had thoughts and presence.
Kazuki tried to scream, but no lungs. He tried to move, but no limbs.
He floated, suspended in something both endless and claustrophobic.
"Ah, a soul. Untethered. And male, no less. A rare offering."
The voice wasn't just in his head—it was his head. It oozed silk and temptation, deep and melodious, but clearly feminine.
"This one is fragmented, but viable. Slightly perverted. Mild addiction to power fantasies. Strong emotional attachments to 2D women. Excellent."
He felt something warm and sticky drip into his mind. He wanted to gag, but again—no body.
"Congratulations. You've been selected by the Goddess of Primal Design to become a Dungeon Core."
"Wait, what?!" he screamed internally.
When Kazuki next became aware of "himself," he was staring at a cavern ceiling made of bioluminescent stone. It pulsed in rhythmic hues of blue and purple, illuminating a surreal landscape of floating crystals, lazy rivers of mana, and—what the hell?
He wasn't seeing with eyes.
He was the glowing core at the center of a crystalline pedestal.
A rock.
He was. A. Rock.
A status screen flickered into view, golden and ancient-looking.
[ DUNGEON CORE ONLINE ]Designation: [Unbound Core – Male Variant]Soul Signature: [Kazuki Hiro]Core Tier: FDungeon Size: 10x10 metersDungeon Points (DP): 25Mana Regeneration: 0.5/secCurrent Affinity: NoneMonster Templates Available: 0Core Form: Locked
"Oh hell no. This isn't happening. Where are the cheat skills? The sword of destiny? The elf waifu who nurses me back to health?!"
He'd read enough isekai to know this wasn't the standard package. He didn't even get a tutorial fairy.
"Initializing introductory protocol. Please do not panic."
Too late.
Suddenly, a humanoid shape began to form from the mist above his pedestal. It coalesced into a voluptuous, eight-foot-tall woman whose very existence defied normal physics. She had horns curling from her forehead, four translucent wings glowing with prismatic energy, and violet eyes that shimmered with stars.
"I am Veyna, the Lustborne Goddess of Design. And you, little core, are going to change this entire world."
"Hi?" Kazuki thought, because again—no mouth.
Veyna smiled like she was used to people being confused.
"Let me explain it simply. You are the first male dungeon core in this world in over 30,000 years. This realm is ruled by monster girls—beings of raw magic and primal need. They bond to dungeon cores to survive, but all the existing cores are female."
"So... I'm rare?"
"You're a walking fertility beacon." She giggled. "Figuratively speaking."
Kazuki processed that.
Then re-processed it.
"Hold up. Did you just say monster girls?"
"Mhm. Lamias, centaurs, kitsune, slimes, harpies, driders—you name it."
"And they all need me?"
"Yes."
"Like, need-need?"
"Yes."
If he had a body, he would've been sweating bullets and adjusting his pants.
Kazuki's inner weeb exploded like a supernova.
"Okay. I can work with this."
Veyna's wings fluttered as she gestured, and a new status panel appeared.
Dungeon Tutorial Unlocked
Summon First Monster Girl [FREE]
Build Basic Room [10 DP]
Assign Guardian Role
Expand Dungeon Territory
"Let's start simple," she said. "Choose your starter. You get one monster girl template for free. Each comes with her own class, evolution tree, and loyalty bond."
Three glowing cards hovered before him.
Kitsu – Novice Flame Spirit (Race: Foxkin)Sassy, clever, and casts fire spells. Great starter magic user.
Gel – Curious Slime Nymph (Race: Slime Girl)Cute, clingy, and adaptable. Learns by absorption. Literally.
Kaelra – Scaled Warden Trainee (Race: Dragonkin)Strong, disciplined, but socially awkward. Natural tank.
"Choose wisely," Veyna purred. "Or don't. Honestly, I just want to see what happens."
Kazuki scanned them all. They were all hot, in wildly different ways. But one stood out.
"Gel, huh? Adaptable, clingy, and... learns by absorption?"
God help me.
"I pick Gel."
The dungeon trembled. Mana surged into the center of the room.
From a bubbling puddle of glowing blue goo, a shape formed. Eyes opened, glistening like sapphires. The slime condensed into the form of a short, busty girl with soft curves, translucent skin, and a face full of curiosity.
She blinked, then bounced slightly.
"Master?" she asked, her voice bubbly and sweet.
"Y-Yeah," Kazuki stammered mentally.
She skipped closer to his core pedestal and wrapped her arms—arms!—around it.
"You feel warm! And tasty!"
"T-Tasty?!"
"Can I snuggle with you forever?"
"I mean, I guess? Wait—what does that even mean?!"
Veyna was openly laughing now.
"Congratulations, Dungeon Core. Your reign has officially begun."
[NEW BOND FORMED: SLIME NYMPH - GEL]+10 Mana Regen / Bonded Hour+Passive Trait Unlocked: Core AwarenessDungeon Growth Rate: +25%
Kazuki suddenly felt the air in the dungeon. He could sense the shape of every stone, every drop of mana, every flicker of torchlight.
And somewhere beneath all the new instincts, he could feel her—Gel—warm and cheerful and inexplicably proud to be by his side.
He didn't know how long this second life would last, but he had a feeling things were about to get way out of hand.
In all the best (and worst) ways.