Volume 1: Boot Sequence – Reincarnated in the Core ✦ Chapter 0: Termination DetectedTokyo, 2025. The rain felt colder than usual that morning.
Satoru Mikami didn't consider himself special. Thirty-seven years old, unmarried, working as a system design lead at a firm he didn't love but didn't hate. Life was… predictable. Stable. Boring.
That changed in under ten seconds.
It happened during lunch—he was walking with a junior coworker, Tamura, and Tamura's fiancée. They were laughing. For a moment, Satoru allowed himself to feel like a main character in someone else's happy story.
Then came the scream. A blur. A man with a knife.
Satoru didn't think—he moved.
The blade buried itself in his gut. Burning, splitting, rupturing something vital. He collapsed to the concrete with his breath caught in his throat.
"Why does it hurt this much?"
His mind was racing. He could feel the life slipping. Cold wetness spreading down his side.
"Don't die! Someone call an ambulance!"
Tamura's voice, panicked. Far away.
It hurt.
But strangely, it wasn't just pain. There was... feedback? A pulsing in his brain. Something synthetic.
SYSTEM INPUT RECEIVED.
"No pain… please…"
Pain Protocol Block initialized.
"I don't wanna die again…"
Self-Reconstruction Preference: High.
"I wish I could make sense of this…"
Cognitive Module Queued: Analysis Priority.
Satoru blinked. Was he hallucinating? There were… words forming in the air? No, in his head. Digital. Cold. Calm. His pain dulled. His thoughts felt organized, categorized—like files being sorted in real time.
"What the hell is going on…?"
He didn't get an answer. Not from the world he knew.
The last thing he saw was the blue-gray of the sky framed by city towers—and the faces of two people crying for him.
He wished them happiness.
LIFE END CONFIRMED. TRANSFERRING COGNITIVE CORE…
LOADING…Formatting new construct…Host environment: unstable. Form: non-humanoid. Executing adaptive shell…
Goodbye, Satoru Mikami.
Hello, Rimuru Tempest.
➤ Transition to Chapter 1
"Okay, this is... very not Tokyo."
"Why do I feel like jelly?"
"…Did I just install an upgrade with my last thoughts?"
→ Proceed to Chapter 1: "My Death, and Why I'm Not Panicking"
📘 Volume 1: Boot Sequence – Reincarnated in the Core ✦ Chapter 1: My Death, and Why I'm Not Panicking (Except I Am)SYSTEM ONLINE.
Cognitive Core: Reconstructed.Host Form: Adaptive Nanogel Shell – Status: ActiveInitializing Perception Subsystems…
Darkness.
No weight. No body. No sound.Satoru Mikami didn't know what to expect from death, but floating in a gelatinous, numb void wasn't on his bingo card.
Then came the awareness.
And with it, panic.
"Wh-what the hell?! What—where the—what is this?!""Why can't I see?! Why can't I feel anything?! Where are my arms?! WHY CAN'T I—"
WARNING: Panic Level Exceeding Threshold.
Engaging Emotional Stability Override……Stabilizing…
Suddenly, the anxiety dulled. Not vanished—just muted, like someone turned down the volume inside his skull.
"What the hell was that? That… wasn't me calming down."
Something artificial was moderating his emotional state.
"You can't just override someone's feelings like that—!"
*Correction: You are currently in critical adaptation phase.
Mental fragmentation may result in system instability.Calm is optimal.*
He tried to scream but had no lungs. Tried to flail but had no arms. And yet… the sensation of presence remained. He existed. Somehow.
"…Okay. Let's pretend I'm not having a breakdown. That seems like what the voice wants.""Satoru Mikami, thirty-seven, definitely dead. Stabbed. Bled out. That part's solid.""So now I'm… what? Data?"
He tried to "move" and—shockingly—felt a ripple in the darkness. His body sloshed. Sloshed.
"Okay. That's new. I have… mass?"
He focused. Pushed his attention outward.
Signal Interface Initializing…
Environmental Scan Active. Range: 5 meters.Substance: Mineral. Condition: Stable.Light source: None.Ether Density: 38%.
Something clicked. He wasn't floating in empty space—he was inside some kind of stone chamber, filled with strange energies. Cold. Silent.
And his body… it felt fluid. Gelatinous, but responsive. He could shift it with thought. Blob forward. Split and reform. Slither.
"Am I… a slime? Like in games?"
He paused.
"No. Wait. No. No way."
He tried to remember the last game he played. Something with leveling systems and ridiculous monster evolution trees.
"Oh god, this better not be one of those Isekai things. I'm not built for this. I didn't even finish Dark Souls."
*Body Scan Complete.
Current Form: Nanogel Construct (Base State).*
Composition: Programmable Matter – Adaptive.Mobility: Rolling / Slithering.Sensory Input: Audio – Inactive. Visual – Inactive. Etheric – Partial.Recommended Action: Calibrate sensory systems and begin resource acquisition.
That cold system voice again. Emotionless, precise. And somehow… comforting.
"Great Sage? Is that you? You sound… more robotic than I expected."
No response. Just a new prompt blinking in his mind's eye.
New Skill Acquired: Gluttony Protocol.
You may now absorb inorganic matter and convert it into code modules and resource components.Would you like to begin?Y/N
He stared. Or… "thought" at the option.
"Sure, why not. What's the worst that could happen?"
He slithered forward. His form bumped into something: a glowing mineral shard embedded in the chamber floor. Instinct took over. Part of him extended—like a pseudopod—and engulfed the shard.
*Gluttony Engaged.
Deconstructing…Data Fragment Recovered: Energy Core (Minor)*New Internal Storage Slot Created.Upgrade Potential: Available (Compiler Inactive).*
It was like tasting power. Not food, but raw information. Like someone had fed him a puzzle piece that made the world slightly less confusing.
"Okay… I think I get it. This body… isn't just alive. It's adaptive. Programmable. I'm not just a slime… I'm a machine made of magic goo."
For a moment, the panic faded completely.
Satoru—no, Rimuru now—sat in silence, absorbing everything.
He was alive. Just… somewhere else. In something else. In a world clearly governed by both magic and code.
"Alright. Don't freak out again. Make a plan. Do the software engineer thing."
He summoned up his voice again.
"System, show me a map… or at least a way out of this dungeon."
*Command Accepted.
Searching for Network Node……No connection detected.*
You are currently in an isolated environment.Exiting will require traversal.
"So I'm stuck. In a cave. As a slime. With no map."
He let his body slump into a wobbling puddle of self-pity.
Then he reshaped himself, slowly, deliberately.
"Alright then. Let's start small. Find an exit. Don't die. Learn how to eat magic rocks.""…Again."
And with that, Rimuru began to move.
→ Chapter 2: "Digital Meets Flesh"
📘 Volume 1: Boot Sequence – Reincarnated in the Core ✦ Chapter 2: Dungeon_Crawl.exe
Mother Log, Timestamp: No idea. Still stuck in quantum jelly form.Environment: Underground techno-magic dungeon.Mood: 80% confusion, 15% dread, 5% really missing instant noodles.
"Okay," Rimuru thought, slithering around another mana-cracked wall. "Let's just accept that I'm a slime now. Not even the fun kind. I'm a programmable gel sack in a world where magic and CPUs had a weird baby. Great."
He rolled forward—literally rolled, since his body now moved like an amoeba mixed with a rubber ball. His nanogel mass adjusted with each bump and slide, leaving no footprints, no heat trail.
Just a low, barely audible ripple as he slid across glowing stone.
"Still, I'm alive. I've got a system interface, an energy absorption protocol, and apparently a growing skill library. I should feel awesome."
"…But this place? This place feels wrong."
He stopped beneath a broken arch—part of a collapsed corridor. The architecture screamed ancient high-tech temple—all mana-circuit glyphs and curved metal fused with stone. Faint lines of power still ran underfoot.
That's when the floor trembled.
Just a twitch. Then again. Then a screech—metallic, warped, and wet.
"That's not ominous at all."
He instinctively ducked back as something lunged from the shadows.
It was the first truly living thing he'd seen here—if you could call it living.
It looked like a tiger made of muscle cables and metal plating, its spine exposed like a data cable trunk. A glowing red sensor-eye flickered in the middle of its skull.
And it roared—a digital distortion over a beast's bellow.
"Okay! That's horrifying!"
*WARNING: Hostile Detected.
Classification: BioMech AberrationSubtype: Vaultspawn / Rogue HybridCombat Readiness: 82%Recommended Response: Absorb / Flee / Die (in that order)*
"Gee, thanks, system."
The thing pounced. Rimuru launched backward with a liquid slap, slamming against the wall—but no pain. Just system feedback: "Impact registered. Integrity stable."
His body morphed instinctively, reshaping into a flatter profile. The beast's claws slashed where his "head" had been.
"Okay, time to test Gluttony on something that fights back."
He lashed out, forming a pseudopod and grabbing a chunk of exposed biomech limb.
The moment he made contact, Gluttony activated:
*Absorption Engaged…
Deconstructing Material…Biological Component Identified: Synthetic Muscle FiberMechanical Component: Hardened Mana-TitaniumMutated Core: Contained.*
Skill Fragment Detected: Reactive Muscle Surge (Physical Boost)Skill Assimilation 38%... 59%... 94%... Complete.
The beast screamed, tried to wrench itself away—but Rimuru sucked the corrupted core right out of its body.
It collapsed, twitching, dissolving into data dust and dark fluid.
Rimuru absorbed what was left. He could feel the energy converting, the core folding into his own system—strengthening his structure, adding a strange surge function to his movement.
"...Okay. That was disgusting. And kind of awesome."
He turned his sensors back on. The hallway was quiet. For now.
"If that thing was guarding something, it must be worth checking."
He pushed deeper into the ruins. Around the corner, two more Vaultspawn were feasting on what looked like a shattered mana conduit—jagged red light spilling into the air like liquid fire.
They turned to him with jerky, twitching movements.
"Yup. Two of them this time. Awesome."
"Alright, Satoru. Time to stop pretending you're in a tutorial zone."
He didn't wait for them to charge. Instead, he compressed his form into a dense, rolling orb and launched himself like a cannonball, slamming into the first with a crushing slap.
As it staggered, he extended a pseudopod laced with reactive muscle and wrapped it around the second one's throat.
Gluttony fired automatically again.
Skill Fragment Acquired: Pulse Edge (Close-range Cutter)
New Passive Module Installed: Dense Core Compression (Minor Defense Boost)*
The battle ended with both creatures twitching in pools of oil and collapsed alloy-organics.
Rimuru pulsed.
His mass shimmered. Something inside him clicked.
A new process had unlocked.
*Compiler Subsystem Awakening…
Advanced Skill Recombination Enabled.*
Would you like to compile new routines from available fragments?Y/N
He paused.
"Wait… I can fuse skills? On command?"
"That's… that's insane."
"…I love it."
He saved the prompt for later, then slithered on, more confident now.
"Not bad for a sentient jelly blob."
Then came the pulse.
Not mechanical. Not biological.
It was like being hit with a wave of divine pressure, ancient and furious and lonely.
Rimuru stilled.
"…That wasn't a monster."
"That was something else."
The corridor ahead led downward—toward the source of the resonance. Toward something old. Powerful. And very much awake.
Rimuru hesitated.
Then pressed forward.
✦ Chapter 2 End
→ Chapter 3: "The Dragon in the System"
📘 Volume 1: Boot Sequence – Reincarnated in the Core ✦ Chapter 3: The Dragon in the System
Mother Log – Entry 08Combat Status: Mostly intact.Skill Count: 4Mental State: 65% calm, 30% adrenaline, 5% "What the hell is that pulsing?"
The pressure was growing stronger.
Each slither forward made the air feel denser—not temperature or gravity, but presence. The kind of presence that didn't need a body to crush you.
Rimuru-Tempest paused on the edge of a stone ridge. Below him lay a massive sealed chamber, ancient and humming with dimensional lock code and shifting glyphs.
In the center, coiled in containment lines drawn in both magic and code—
"Holy sh— Is that… is that a dragon?"
It wasn't just any dragon. It was huge. Regal. And obviously pissed off.
The beast stirred. One glowing golden eye flicked open.
"...A visitor?"
Mother Log – Entry 09New Entity Detected.Mana Pressure: Unsafe at all distances.Hostility Level: Unknown.Recommendation: Don't be dumb.
"You know, I didn't come here to meet literal boss monsters."
But something deeper stirred inside Rimuru-Tempest—a kind of strange familiarity. Not fear. Not awe. Something closer to…
Recognition.
The dragon turned.
"You're not a human."
"Nope. Reincarnated slime. Sort of. Also... hi."
"...Reincarnated?" the dragon's voice deepened."Intriguing. And you do not tremble before me?"
"I'm panicking internally. Believe me."
A long pause. The dragon blinked.
"Then perhaps… we can talk."
✦ Chapter 4: Stormlocked
Mother Log – Entry 10First Real Conversation: With a divine-tier dragon.Odds of surviving: 50/50Emotion Status: Equal parts horror and curiosity.
"I am Veldora, the Storm Dragon," the beast said, stretching its wings slightly, shaking the dimensional code-seal."Imprisoned here for three hundred years."
Rimuru-Tempest resisted the urge to gasp or make a Godzilla joke.
"How're you still sane?"
"I'm not."
"…Good talk."
They did talk, though. For hours. Maybe days.
Veldora ranted about humans, magic, betrayal, loneliness, missing books, and an unhealthy obsession with pudding. Rimuru-Tempest mother-logged the whole thing.
Mother Log – Entry 14Observation: Veldora is terrifying… and lonely.Secondary Observation: He might actually be my first friend.
"You're not like the others," Veldora said, lying down with a huff."You don't recoil. You don't kneel. You just… speak. Why?"
"Because I'm not from here. Because I've already died once. Because none of this makes sense, and you're the first person that hasn't tried to kill me yet."
"…Interesting. Then let us form a bond. A pact, if you will."
"Pact sounds like a really powerful word—"
"I shall give you a name."
✦ Chapter 5: The Naming Protocol
Mother Log – Entry 16Situation: Dragon wants to name me.System Response: Freaking out already.Emotional Response: …I don't hate it.
"From this moment on," Veldora said, "you shall be known as Rimuru… Tempest. Rimuru, for the flow of your body and your mind. Tempest, my family name, for you are now part of my kin."
"Wait what—"
SYSTEM CRASH IMMINENT.
*Name Protocol Engaged.
Unique Identifier Registered: Rimuru Tempest.*
Lineage Tag: Tempest – VeldoraSystem Access Tier Upgraded.Compiler: Unlocked.Core Expansion: Quantum Core v1.2 Initialized.
Mother Log – Entry 17Pain Level: Technically zero.Agony Level: 10/10Transformation Status: Undergoing massive internal rewrite.
His nanogel body exploded in fractal lights and shifting patterns. Rimuru Tempest twisted, expanded, liquified, compacted—all at once. It wasn't pain, but it was intense.
The system was rewriting his existence.
He felt every data thread realign, every molecule of code-laced gel take on new logic.
When it ended, he was… whole. Stronger. Stable. Named.
"…Damn."
"You lived," Veldora said, chuckling."I expected a meltdown."
"Oh, I definitely melted something."
✦ Chapter 6: System Recompile
Mother Log – Entry 18Current Status: Post-name high.Stat Window: Fully online.New Directives: Explore, Survive, Become Something Worth Naming.
With the name came a flood of new access. New routines. New abilities.
➤ Core Upgrades:
Compiler Online – Combine absorbed skill fragments into advanced routines.
Core Density Enhanced – Better defense and impact resistance.
Memory Space Unlocked – Can now store entire object/skill blueprints.
Daemon Thread Support – Can spawn minor autonomous "threads" of himself.
"I feel like a whole operating system now."
Veldora nodded sagely.
"You were born undefined. Now you are real. The world will know you. Rimuru Tempest, first of the Slime-kin… and my sworn family."
"…Thanks, big guy."
The chamber shook.
Not from Veldora. From above.
Mother Log – Entry 19New Threat Detected: Multiple mana signals converging near vault entrance.Something… woke up.
"I think your naming ritual just set off some alarms," Rimuru muttered.
"Oh," Veldora said. "That's… probably bad."
→ End of Volume 1
📗 Volume 2: System Reboot
The world has taken notice of Rimuru-Tempest. The vault is no longer dormant, and something above is moving. But so is Rimuru. Reborn, named, and evolving… he's ready to touch the world beyond the dungeon walls.✦ Book-Length Chapter: "System Reboot"
Mother Log – Entry 20Name: Rimuru-TempestCore Status: Fully RecompiledCompiler Tier: ActiveMission Objective: Ascend, Explore, Survive
Part 1: Waking the System
After being named, Rimuru-Tempest enters a stabilization period. He can feel the Vault itself reacting to his presence now—doors sliding open, sealed passages unspooling, long-dead systems whispering to life.
The Compiler shows new options:
Merge skill fragments into full battle routines.
Build combat subroutines from memory (ex: tendrils + energy pulses = Lash Nova).
Create Daemon Threads—tiny pseudo-intelligences derived from himself to scout or fight independently.
He tests them with Veldora, who watches like a proud chaotic uncle.
"You're no longer just adapting. You're evolving. This world's not ready."
But something stirs far above.
An Aether Beacon pulses—a failsafe that detected the dimensional fluctuations of Veldora's seal destabilizing. A signal has been sent.
Mother Log – Entry 23Update: We may have triggered a planetary alarm.Recommendation: Don't stay long.
Part 2: Surface Response
Above the vault, the hybrid world is already responding.
From the Technomancer Nation of Aegiron, a unit of Magitek Adventurers is dispatched. These are elite scouts that combine biological enhancements with rune-cybernetics.
They descend using void-drop capsules and begin breaching the vault's upper layers.
Their orders: Investigate the signal. Secure or destroy what's inside.
They're professional, armed, and underestimate what they're about to walk into.
Part 3: First Contact
Rimuru-Tempest's first encounter is with a recon unit of three:
Kallan-01 – AI-linked scout with thermal and etheric sensors.
Yuni-Theta – Aether manipulator with pulse grenades and mana siphons.
Razor-Mirth – Heavy-armored tank, enhanced muscles, powered axe.
They breach a hallway near the chamber—cutting through a door Rimuru-Tempest had avoided.
He watches from the ceiling, using a Daemon Thread to scout.
Mother Log – Entry 27Visitors: Definitely not friendly.Subgoal: Survive without letting them data-vivisect me.
He listens. They speak modern hybrid-common, peppered with system-slang. They mention:
Vault Tier classification
"Possible rogue Aether entity"
"Extraction priority: synthetic lifeform"
They think Rimuru-Tempest is equipment, not a person.
He introduces himself by launching Lash Nova into the ceiling and collapsing half the corridor on them.
Part 4: Battle for Identity
The full fight is brutal.
Rimuru-Tempest uses modular tactics: splitting his body into mobile combat threads, forming reactive weapons with Compiler, and using environment manipulation.
The enemy adapts quickly, forcing him to upgrade live using Compiler access:
Pulse Edge + Reflex Muscle = Auto-Counter Lash
Gel Body + Mana Shield Fragment = Phase Displacement Coat
But even as he defeats them, he realizes something terrifying: they aren't the strongest. They were just the probe.
Mother Log – Entry 30Conclusion: The surface world has changed.They've built a civilization that talks in spellcode and shoots magic like bullets.
I don't belong here.But I might be the only thing that can still speak to both sides.
Part 5: Ascension
After securing the chamber and absorbing their remains (data only, not life), Rimuru-Tempest prepares to leave the Vault.
He and Veldora exchange a final moment before parting.
"We'll meet again," Rimuru-Tempest says."The world's broken. Maybe I can fix part of it."
Veldora laughs.
"Then go, Rimuru Tempest.Be the glitch in their system."
He ascends.
Through the ruined stairwell. Past ancient defense systems, now silent. Through blast doors etched in forgotten runes.
He emerges into the open world—under a blackened sky.
And sees it for the first time:
Floating citadels pulsing with reactor mana.
Mega forests corrupted by rogue spell-data.
Artificial weather nodes holding the climate together with duct tape and rituals.
And far, far in the distance—a tower of light piercing the heavens: the capital of Aegiron.
Mother Log – Entry 32Environment Status: Chaotic balance.Systemic Layer Conflicts: Magic vs Tech.My Position: Unknown anomaly.My Goal: Change everything.
End of Volume 2: System Reboot