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Rating:
Mature
Archive Warning:
Creator Chose Not To Use Archive Warnings
Category:
F/M
Fandoms:
無職転生 異世界行ったら本気だす - 理不尽な孫の手 | Mushoku Tensei: Isekai Ittara Honki Dasu - Rifujin na Magonote (Novels)無職転生 ～異世界行ったら本気だす～ | Mushoku Tensei: Isekai Ittara Honki Dasu | Jobless Reincarnation (Anime)呪術廻戦 | Jujutsu Kaisen (Anime & Manga)
Relationships:
Paul Greyrat/Zenith GreyratLilia Greyrat/Paul GreyratRoxy Migurdia/Original Character(s)Sylphiette (Mushoku Tensei)/Original Character(s)Eris Greyrat/Original Character(s)
Characters:
Ivar GreyratZenith GreyratPaul GreyratLilia GreyratSylphiette (Mushoku Tensei)Roxy MigurdiaEris GreyratGhislaine DedoldiaPhilip Boreas GreyratHilda Boreas GreyratSauros Boreas Greyrat
Additional Tags:
Family FluffAction/AdventurePersonal GrowthSelf-InsertWholesomeHeavenly Restriction (Jujutsu Kaisen)Identity IssuesPsychological ThemesCanon DivergenceSlow Burn
Language:
English
Stats:
Published:2026-02-12Updated:2026-02-12Words:40,351Chapters:4/?Comments:7Kudos:44Bookmarks:13Hits:1,686
Mushoku Tensei: Heavenly Restricted
TheUnfuzzyFabulist
Summary:
It starts close enough to feel safe. Close enough to be a mistake. By the time the differences become obvious, the story has already moved past the point of fixing them. They would all bear witness to the bare flesh of the one who is truly free. The one whose unwavering spirit guides him through every trial with his overwhelming tenacity!
(MT SI-OC with a Heavenly Restriction)
Chapter 1: The Scar of a Second Chance
Notes:
Hello. This is a Mushoku Tensei x Jujutsu Kaisen fanfic.
This story has been stuck in my head for nearly two years. I know there are other works out there with similar setups, but this one wouldn't go away. I had to write it just to get it out. It's not about power levels or flashy spells. Most of it is just people talking, thinking, living. A slow burn, with more attention on mood and everyday moments than big events.
Part of the push came from Mushoku Tensei: Moving Forward by crashclown. It takes an unusual route and avoids the usual clichés. I didn't agree with every choice it made, but it stuck with me. I'm not lifting anything from it, but reading it made me want to try writing something that leaned more into atmosphere and restraint.
That's all. Thanks for giving this a chance.
If you've got time, I'd appreciate a review. Honest comments are welcome, especially the blunt ones. I want to do better.
(P.S. This author's note was originally posted on FanFiction.net.)
(See the end of the chapter for more notes.)
Chapter Text
There's a strangeness to the university once the sun withdraws. The ceiling lights stutter in uneven intervals, casting a pale wash that fails to anchor. The air feels filtered beyond usefulness, drained of weight, handled by too many machines for too long.
The projector issued a mechanical click as the final slide collapsed into black.
"That's all for tonight," I said, checking the time. "Treat your smooth muscles with care. They're still on shift, whether you are or not."
The lecture hall rose in a slow gradient. Students were scattered across the rows, some already loading bags, others collapsed into the posture of people worn down by repetition.
First-year forensic science majors. Promising in documentation, drained in practice. Human Anatomy and Physiology was meant for the early hours, yet somehow, it was shoved into the final stretch of the day. And Judging by their faces, none of us were thrilled about the schedule.
"You're dismissed," I said, dragging a knuckle across my chin. "Take your trash with you this time. The janitors have complained enough, and I'm not dealing with it again."
Chairs scraped across the floor as students stood and shouldered their bags, the weight of the day evident in every motion. The door creaked open, just slightly, when something tugged at my memory.
The realization clicked into place with a snap of my fingers.
"Wait," I said, already standing straighter. "Where are your submissions?"
The room answered with a low exhale.
"I thought it was online."
"My printer broke."
"We had three other deadlines today..."
I couldn't help but snort. "Excuses noted. The work still wasn't submitted."
They approached one at a time, depositing their work with varying degrees of care. Several papers were worn at the edges. A few had stains. One bore the imprint of a… shoe across question three.
Yeesh. At least try to make it look like you cared.
Then the final student stepped forward.
I recognized him. He always sat by the window, kept to himself, and never strayed from the routine. He wasn't unfriendly, but rather, his behavior is marked by intention rather than distance.
Tucked at his side was a paperback. The cover gleamed with fresh, sharp colors, crisp and pristine. The illustration on it immediately caught my eye.
Brown hair. Green eyes. A young man, drawn mid-step.
Mushoku Tensei.
"You're reading that?" I asked.
The student blinked, caught off guard.
"Y-yes, sir. You've read it?"
"I have. A long time ago. I stopped around volume eleven. That was when my evenings got swallowed by committee work."
His expression shifted subtly, but it wasn't forced.
"I'm at volume twenty-one," he said. "The story changes shape later on."
"Ah, I see. Well, keep that to yourself," I said, placing his work on the stack. "I might return to it when time allows."
"Alright, sir," he replied. "I hope you give it another shot someday."
He raised a hand slightly as he turned to leave. Not quite a wave, just a small, respectful gesture.
The door clicked shut behind him. The silence that followed wasn't comforting, but it wasn't heavy either. It simply settled, as if it belonged there.
I remained still for a moment, then exhaled and began the routine.
I started with the papers of the students, stacking them neatly and aligning the corners without haste.
Next were the cables. I unplugged the HDMI, coiled it slowly, and set it aside. I closed the laptop with care, slid it into its sleeve, then placed it in the bag. The charger followed, unplugged and stored.
With that, I carried the bag and the papers. At the switch, I turned off the lights. They blinked once, then faded to dark as I closed the door behind me.
Outside, the hallway was dim, lit only by a few remaining bulbs that cast faint reflections across the floor tiles. The air carried a trace of disinfectant and old wood, a smell that recalled empty clinics after hours.
I chose the longer path back to the faculty office. A few windows still glowed in the distance. Another cluster of buildings stood in near darkness, their glass panes reflecting what light remained. Farther uphill, most structures were completely shadowed.
When I entered the faculty room, it was quiet and orderly. Everything was in place, the space already winding down for the day.
I went through the usual procedure, closing the drawers and shutting down the terminals.
At the key rack, only one remained. Mine.
I began sorting, merged the papers into a single stack, labeled them with the course and year level, tied them together, then filed them into the cabinet. Locked it. Sat back again.
I stretched. A small yawn came and went.
The wall clock read 7:59 PM.
One minute before eight. That should've been my cue to leave, but I stayed in my seat.
My apartment was a few streets out. Not far, but not exactly close. It sat on the fourth floor of an old building. The hallway tiles were cracked in places, and the stairwell window had tape across it that didn't do much against the rain.
…I should really find a place closer to campus.
I leaned back, eyes tracing the ceiling. There was still time. Roughly an hour before the night guard began his sweep. If I left by 8:10, I had a decent chance of catching a jeep without much waiting.
So I closed my eyes, folded my arms. Let myself sit still.
My mind wandered to one of my students. The one who brought the book.
Mushoku Tensei. A story about a ruined man given a second chance. It's pedophilic, overly sexual, and hard to defend. But I wasn't drawn to that. What stayed with me was his struggle to grow, to become better than who he used to be.
I'd seen the anime before and only made it through part of Season 2, but holding the printed version felt different. It made me want to read it properly. Online, at least.
Still, when was the last time I read anything that wasn't a thesis, a module, or someone's final paper?
Nine years. I've been teaching that long already.
"…Tch. My thoughts always spiral when no one's around," I muttered. "Might as well reward myself with a decent cup of coffee."
Then I heard it, soft at first, growing clearer with each second. I turned toward the window, squinted, and let out a groan.
"Naturally. Just my luck."
Rain. Not even a drizzle, but a steady, relentless downpour.
I walked up to the window, confirmed it, and sighed. Looks like I'll be here longer than I planned
Back at my desk, I pulled out my phone, hoping it might help pass the time. I opened Facebook out of habit, but Messenger popped up right away. Unread messages. Group chats. Mostly work… Another meeting on Saturday? Of course.
I locked the screen and slipped the phone back into my pocket, not really in the mood to deal with any of it.
For a moment, the silence returned. My thoughts wandered back to the book again.
"A second chance, huh," I muttered.
Everyone deserves one. And I understand the appeal, to change yourself entirely. But one must know the difference between fiction and reality.
Even so, I believe in it. Even if it sounds naïve.
People speak of second chances like they come wrapped in certainty. As if making a different decision at the same point would erase everything after. But it doesn't. A second chance just means doing things again, with better timing, maybe, or less fear, but the same limitations still follow. The same self, most of the time.
Huh… maybe I do need to read the light novel. Why am I even thinking like this?
I yawned.
Ah. This wasn't good. I'd doze off if I stayed like this.
But… I do deserve to rest, right? Just a bit? Fifteen minutes wouldn't hurt.
I turned my phone back on, set an alarm, then buried my face in my arms. Just fifteen minutes. I'd wake up. Hopefully the guards wouldn't start their rounds too early.
I took one last look around. Only the hum of the lights filled the room. Materials and desks surrounded me, my fellow faculty, friends, acquaintances.
I thought about how all of this started. How easily it might've gone another way. How…
…
No. I think this is fine.
With that, I closed my eyes.
And everything went still.
[Initializing Biological Integration...]
Huh?
[Loading neural pathways...]
[Spinal matrix formation: 42%...]
[Muscle density anomaly detected.]
[Processing...]
Wait. What?
Everything was black, not calm or kind, but dense, as if the dark had thickened into tar, pulling everything inward. I couldn't tell if I was sinking or pinned in place, only that the warmth stuck too close, not to soothe but to smother, while the silence spread out forever, with no rim or mercy.
[Accelerated physical template: Approved.]
[Warning: Mana Circuitry... Not Found.]
[Implementing Heavenly Restriction.]
The hell?
Heavenly Restriction… like Toji? From Jujutsu Kaisen?
[Heavenly Restriction Sync: 28%...]
This had to be a dream, one of those lucid nightmares where nothing followed logic, a scrambled mess my brain stitched together while sleep dragged me under.
[Warning: Incomplete Organic Scaffold. Malnourished state detected.]
[Bone density: 0.62 standard. Muscle tissue: Below threshold.]
[Survival probability upon delivery: 38%.]
…Delivery?
[Foreign soul signature detected within vessel.]
[Conflict level: Critical.]
[Stability compromised. Executing overwrite protocol.]
What?
[Overwrite sequence engaged.]
[Preserving dominant signal...]
[Secondary presence... terminated...]
[Residual anomaly archived.]
The void distorted, waves of static folding over themselves as if reality exhaled in slow resistance.
[Integration stabilized. Host synchronization at 100%.]
[Initializing Weapon System...]
A what now?
[Tool Database Sync: In Progress...]
Images flashed through my mind too fast to follow. Weapons, tools, outlines I almost recognized. Some felt familiar, others completely alien. I couldn't make sense of any of it, but I knew I'd seen them somewhere before.
Was this some kind of high-stakes gacha simulator? A broken system scrambling through my head like it was pulling loot from corrupted data.
[Weapon Sync Complete.]
[Tool Database Sync: Finalized with exceptions.]
[Tools Integrated into Mental Inventory.]
[Adjusting Physiology for Compatibility...]
Then came pain, not sharp or sudden, but deep, a slow warping that wrenched my bones into wrong angles and methodically shifted my organs. Something was rewriting me from the inside out. I wanted to scream, yet nothing remained to scream with, only a leaden heaviness where my limbs should have been, each throb compounding into a relentless, grinding ache.
…
…
And then it stopped. Oh God, that was no dream. I felt every bit of it.
[Delivery in T-minus: 00:01:48...]
Delivery. That word again. What even was this? Could it really be a dream?
[̵̙͉͐̅́̂̈́ͅ ̵̫̫́͂͌͘D̵̠̆̾Ơ̸͓̺̻̲̹̊ ̷̢̍Ñ̶̢̨̝͓̐̓͘͠O̴̜̲̫͑̈́T̵̠̼̟̄̏ ̷̛͈̣̩̆̐͝I̸̙̰̝͒̇͒N̷̙̑͗ͅT̸̛͉̈́͆͝E̶̛̤̥̱͚̟̅́̿͂R̸͚̪͙̜̔̀̾R̷̡͂͊͑U̴̦̗̤͕̝̒̒̽͋̃P̸̤̟̽̿̓͊͜T̷͍͉̰̈́̈ ̷̢̱̙̋̅́͐͜T̷̤̓͒̇̔͝H̶̨͌͊̆͝E̸̞̲̔͛ ̶̝̀̾̒P̶̯̎̈́R̵̢̜͖͚̻̐̏̿̚O̴̰̒Ć̴͈͈͎̦͈́͝͝E̶̢̨̩̩̝̔͋̓̅̈́S̵͎̻̞̭̺̊͗S̵̡͓͓̹͊̿̓̋̓ ̶͉̥̫͍͙̉̋]̵̛͓̹̥̑̑̈́
A flash of red ignited my thoughts before they dissolved into static, leaving me unable to move or think, only to exist while the system tore through me, a corrupted install grinding its way inside.
My mind was slipping, thinning out into oblivion, but I caught one last thing.
[Integration complete. Collateral anomaly unresolved.]
[Welcome to the world, User.]
And then, nothing.
The moment awareness seeped back in, I half-expected to find myself under the glare of the faculty room lights, cheek stuck to my desk, the night guard telling me to go home.
Instead, what greeted me was something older and crueler.
Hunger.
Not the dull pinch of an empty stomach, but a vicious gnawing that scraped at bone and marrow, a void that felt as though it had been festering in darkness longer than thought itself.
My breath snagged in my raw throat, and from my lips spilled a hoarse, alien cry.
"Bwaaaaaaa!"
The sound startled me. A ragged, hollow wail that didn't feel like my own.
Panic gathered behind my eyes, pressing to break through, but before it could spill over, I forced my body to move, anything at all. Nothing answered. My limbs lay inert, heavy and numb, as if they no longer belonged to me.
"H-Hylas alva! Oth gathil Dios!"
A voice cut through, shaky yet edged with relief, feminine and young, and far too close for comfort.
I tried to force my eyes open, but my eyelids stayed shut, heavy and unresponsive. All I could feel was the raw ache tearing through me.
"BWAAAAAAH!"
Another ragged cry tore its way out of me, and though something deep inside screamed that everything was horribly wrong, the hunger chewing through my core drowned out every thought.
"Thala Zenith, kural na. Melin iskal falan!"
Hands lifted me from cold into warmth. Cloth brushed against me and the faint sweetness of skin reached my senses.
Then something soft and warm pressed against my lips.
Instinct overruled hesitation. I latched on, and warm milk spilled into my mouth. Strange, but my body seized it like it had waited an eternity. I swallowed in desperate gulps, the emptiness inside roaring louder than thought.
But as the sharpest edge of hunger dulled, reason fought to surface.
I remember dozing off in the faculty room, then… nothing. Maybe I blacked out, had a stroke, or worse, but I woke without the sharp sting of antiseptic in the air, no mask on my face, and no hospital sheets under me. Was I kidnapped? God, please, I don't want my organs carved out.
With effort that felt like tearing my very soul, I forced my eyelids open.
The world swam into view, blurred and unsteady, lit not by fluorescent light but by firelight. Shadows shifted across a rough-hewn wooden ceiling, and in place of beeping monitors, there was only the soft crackle of candles in the stillness.
My vision steadied enough to see a beautiful young girl with fair skin and hair the color of ripe wheat, her eyes heavy with exhaustion.
…This clearly isn't a hospital.
I strained to see beyond her shoulder. A young man stood watching me, jaw clenched, worry etched deep into his brow. Beside him, a slender maid in an elaborate uniform that looked torn from the pages of a medieval fantasy.
Everything around me felt absurdly out of place… and far too large.
"Zenith… inar vel iwa… da'vel lin orla?"
The man finally spoke, his voice low and heavy, shaping words in a tongue I couldn't even begin to place. It wasn't English, nor Russian, nor Mandarin… nothing I recognized at all.
"Tholin. Kulan, mel… valas ha. Yna don vilth si…"
The girl drew me closer, holding me tight against her chest.
Judging by their faces, their towering size, and the strange weight in my own body, there was only one conclusion left to draw.
This can't be what it looks like. Surely it's nothing more than delirium, a fevered vision born of hunger and confusion. Right?
But when our eyes met, she offered a trembling smile.
"Asha… Ivar. Len'var tal witha."
The words meant nothing to my ears, yet something in the way they caught in her throat sank into me. I lay helpless in her arms, my heart hammering against ribs that felt too soft, too small. Part of me wanted to deny it, but another part of me already knew.
This wasn't delirium.
I... I had been reborn.
Notes:
I won't spoil anything, but here's one thing. Rudeus won't be part of this story. Not at all.
As for why… you'll see. That's all I'll say for now.
Thanks for reading! If you feel like leaving a review, I'd really appreciate it. Honest thoughts, blunt or kind, are always welcome.
(P.S. This author's note was originally posted on FanFiction.net.)
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