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Theory of Relativity

Summary:

After losing your fiancé, Gojo Satoru, grief pushes you to unravel fate itself. Using all your knowledge from your past life, your attempt to play hero fractures the life you once knew. Old memories fade, and the world shifts into something unfamiliar, leaving you to wrestle with the fear of losing everything you once had all over again.

A fix-it fic, though the “fix” comes at a cost because it's jjk

Chapter 1: Prologue: Absolute Zero

Notes:

Hi! My writing style has definitely evolved the further the story advances, so if you're a stickler for writing like I tend to be, I promise it'll get much better! Thank you so much for clicking on Theory, please enjoy and feel free to comment :) I try to answer everything!

Chapter Text

Time was a fickle thing, you of all people knew that.

A simple unit of measurement that has come to represent experience; a notion that should not be tampered with. Time brings about a myriad of emotions and, sometimes, it seemed difficult to accept. Other times, you refused to accept it at all, choosing instead to rewrite it to your own standards.

Five months ago, you sat across from your then boyfriend, Gojo Satoru, on what you thought was just a normal date. Yes, it was fancier than most of the things the two of you enjoyed, preferring fast food over a lavish night out. Nevertheless, you were glad just to spend time with him, and when he grabbed your hand, dragging you out to the balcony to ask for your hand in marriage, you were the happiest you had ever been. 

You had known him since high school, the beginning of your relationship tumultuous, consisting of petty fights and rivalry. Turning 20 had changed that, the two of you maturing(if you could call Gojo mature), into young adults that had more in common than they had thought. In time you had become the pretentious Jujutsu Tech teacher and his endearing coworker.

Your life wasn’t unfamiliar with loss. In your line of work you had lost many friends, but the last year has taken so many of your loved ones. Despite that, it did nothing to prepare you for losing the man you love. 

You’d give anything to go back to when this all began. Where his persistent, annoying voice was the worst of your concerns. You wished that, in this moment, you could hold onto the belief that he was really ‘The Strongest’.

He had sworn to you with that cheshire grin of his, that in a fight against Sukuna, he’d win.

So why?

Why was this the outcome? How was the Gojo Satoru losing?

He had always had the underlying callous attitude. It had taken root after the events post the Star Plasma Vessel debacle and only grew thicker when Geto had-

Yet, there was some part of him that still held on hope for Megumi Fushiguro, so like a fool he recklessly threw caution to the wind and did his best to try and save him. 

In theory, there was no way that an object could ever reach absolute zero. But now, it certainly felt like the bottom didn’t exist, that this free fall was never coming to an end. It was as if Ryoumen Sukuna had delicately strung you along his spider web of abolition, only to rip its supports from around you, letting you fall into the depths of despair.

The next thing you could see in the chaos around you was the dust and smoke that settled over the ground. You had tried your best, truly, but you were no doubt helpless in this situation.

Your legs had been crushed, upper body just out of harm's way of the building that had fallen on top of you. You knew even if Gojo had won, this likely would’ve ended in your death. But that would’ve been okay.

Selfish or not, your death would’ve been Gojo’s to deal with.

You realized, over your lamenting, that the battlefield had grown quiet. No more yelling, no more cursed techniques, and no more struggle. For a moment, your heart began to spike with hope. There was no laughing. No cruel, imminent danger looming around you.

With a new found purpose, you began to push, your muscles burning, willing your body to move forward even just a few steps. It was as if a fire had set off inside you, sparks cracking to life in the form of your tendons. Everything hurt.

You cried out in frustration, body refusing to cooperate as you fell back to the ground. You couldn't even feel your legs at this point, so even if you could escape, would you be of any use?

“Fuck…” Your voice came out broken and unrecognizable, followed by a series of dry coughs. You had breathed in so much shit your insides ached. You spoke to no one but the voice in your head, your consciousness annoying you to no-end, even now.

With all the strength you had left from your prior attempt, you managed to prop yourself onto a slab of concrete, hand scrambling as you grappled with the steel beam attached to it. If you knew any better, you’d say this used to be a balcony, belonging to some innocent family who had been caught in the struggle. Your hand finally secured around it, a pitiful groan releasing from your throat as you pulled forward, legs sliding from underneath the rubble that caved over you.

Just beyond the wreckage had been where the fight was held, and soon enough, you’d come across the scene again. The thought of being closer to Gojo alone was enough to push you forward, hands clawing at the ground as the uneven ground tore up at your nails. You had gotten them done recently, white flowers now stained red as blood seeped from beneath your nail beds. What a waste of perfectly good money.

You realized that no matter what you did from now on, there would be no way of stopping any more senseless tragedy. Your end seemed to be approaching now at a relaxed pace, in no hurry as he knew you had nowhere else to go.

Ryoumen Sukuna stood a few meters from you in the body of your student, Megumi Fushiguro. If it weren’t for the undeniable reality that you’d never see Gojo again if you didn’t do something, you’re sure this would've broken your heart. The sadness that flooded your senses wasn’t enough to quell the pure, unadulterated hatred you held in your heart.

Your students seemed to be a weak point for you, and it had been exploited on this battlefront, time and time again. The thought of Sukuna’s demonic, barbaric heart corrupting the soul of poor Megumi was enough to freeze you where you stood.

A little bit past him laid the body of your fiance, the center of your universe as you knew it. There laid Gojo Satoru, or—for lack of a better term, Gojo’s bisected corpse. His torso was separated from his legs, black shirt slacked against his stilled chest. But even in death, he was beautiful. His pristine blue eyes stared wildly at the sky, as if the gates of heaven had opened for him to greet him with an angelic chorus.

Your lips trembled, eyes widening so far you’re sure they’d pop out of your head. Your ears rang with blood rushing through them, deafening you to all other sounds except for Sukuna’s steady footfalls. The excruciating pain of blinding yourself would be a better experience, than to sit and cry like a baby as your fiance bled out hopelessly in front of you. You looked up in a daze as you saw that Sukuna was now only a short distance away.

Your eyes screwed shut, the bones in your legs cracking as you forced yourself to stand, trembling in their wake. You wobbled, stumbling forward as you slid down the side of the crater, rolling onto your back as your leg was pulled out from beneath you.

“You know, I thought you’d be one of the first to die. Sobbing like a bitch as I forced Gojo to watch you choke.”

Those words struck you to your core, eyes snapping up to take in the sneering expression of the bastard hovering over you.

“You’re stronger than I gave you credit for, Obinata Y/N.” He spoke your name like a curse, like your very existence was a mockery to the world. He pulled back, pivoting on his foot as his hands rested in his pockets. “But not strong enough.”

You yelled something, but it came out incoherent. An inhuman noise left your throat as you reached out, hand wrapping around Sukuna’s ankle. “Megumi…! Fushi-” You tried in vain to get through to him, desperately calling his name.

“Oh, him?” Sukuna sneered. “He’s given up, woman.” The glare he threw back your way was enough to silence your wails, his movement coming to a stop. “And so should you.”

The next thing you knew, your voice crescendoed into an animalistic howl, Sukuna’s foot coming down to crush your hand, fingers shattering underneath his weight. With as much energy you could muster, you tried to use your ability.

Gasping, you found yourself flat on your back again. Your lungs contracted, desperate for air, ribs refusing to loosen around your diaphragm. You pushed yourself up and held back a sob as you saw Sukuna back to where he was only seconds ago.

“You can’t be serious, you really lost against that guy?” Gojo’s voice rattled in the back of your head, nothing but black spots interrupting your vision. “Man, if only I was there to see your face!”

Life was simple when you were young. When Geto was still alive, your class of four would all have weekly game nights. Gojo would inevitably cheat everytime, just to get a rise out of Shoko. Then, as if Yaga-sensei could sense the rising tension, he would come in to yell at your group to ‘go the hell to sleep’. Gojo would drag Geto off, the two of them laughing wildly as you and Shoko would be stuck with clean-up.

Two pairs of hands grabbed you by the waist, pulling you to their sides, squishing you between them as Shoko squatted in the front, throwing up a peace sign. You tried to resist a grin but failed as Gojo had joked, “Everyone say, ‘Yaga smells!’” Only to get smacked in the back of the head by the man himself, standing to his left.

If only you were there instead.

Sukuna looked at you, a breath escaping his lips as he took in the change. You had moved him back. Most enemies wouldn’t have any awareness of your abilities. When you reversed time, you reversed the minds of others with it. Most had been ignorant to the manipulation of time, but not the King Of Curses.

His eyes narrowed in thin slits, pupils dilating into black holes, sucking in the light around you like a vacuum. You watched as his veins pulsated, creating a map of fury across his skin. The corners of his mouth had twisted downward, pulling themselves into a thin, unforgiving line.

“I’ll humor you.” He spoke, before his shoulders pulled forward, muscles taut, readying himself to launch towards you. He had every intent to murder you now, but that didn’t mean he couldn’t have fun while he did it.

Racing forward at unimaginable speed, his fist collided with your face. You flew back, a pathetic yelp cracking from your lips as you rolled violently across the ground. As you looked up, he was there. Your eyes widened at the close proximity, and you could feel as if time slowed. His fist was reeled back, cursed energy imbued into his punch. You managed to roll out of the way in time to see the ground split open where you just had been. Holy shit.

“Having fun yet?” He taunted, head abruptly twisting to stare at you. He straightened up, walking closer.

The scene glitched before him, and he blinked– hoping to see through the rewind, he focused intently. To no avail, he was brought back to yet another passing moment.

Now, he was still above you, but you had already predicted his movements. As his fist shot downwards, you snaked yourself in between his legs, choosing to forego your previous action of rolling out of the way.

He let out a growl, and it quickly turned into a groan of annoyance as the back of his knee was kicked in. He kneeled forward, Megumi’s body not as physically strong as he’d hoped it would be. Of course, the boy was only 15.

By the time he had turned to face you, you were gone. Using the moment of surprise, you had made a last ditch effort to get to Gojo.
He was there before you could get any further, the sheer force of his movement sending you skidding backwards.

“Get out of my way.” You don’t know what force compelled you to say that, but the words flew out without a second thought. Your breath staggered, one of your eyes twitching to a close, blood from your previous injuries running down your head. It coated your eyelashes, the sickly sweet, metallic scent filling your nostrils.

“This is starting to annoy me, girl.” He uttered darkly.

“Yeah?” Your lips pulled up into a smile. Hell, if you were going to die, might as well die smiling. “I’m sorry you feel that way.”

“How long can you keep this up? I could just kill you, you know.” He wasn’t sure why he hadn’t just grabbed you, knowing you weren’t putting up much of a fight before. He could’ve saved himself the time.

What a glorious curse time was.

“You’d have to catch me first, bastard.” Your hand came up to wipe the blood that dribbled down your chin.

“Is that a challenge?” His eyes piqued up in interest, hands clutched at his sides.

You sneered. “It’s a suggestion.”

Though Sukuna was an unbelievably strong fighter (considering he defeated Gojo minutes before), he was predictable in his aggressive fighting technique. Every hit he landed, you threw back two. It was an exhausting game, and you knew eventually you’d never make it out alive if it continued this way.

In your youth, despite your rocky relationship in high school, Gojo had given you a necklace. The silver chain was beautiful on its own, but the main star of the show was the hourglass attached to it. It was small, but completely functional. While the gesture seemed innocent, it had rooted a deep sense of belonging within you– and this necklace, which you still wore to this day, contained an abundance of your cursed energy.

To be rightfully honest with yourself, you didn’t know what you had been storing it for. Now, it all made sense. Time and Fate walked a thin line together, and this was just meant to be.

You grew up in a “righteous” clan. The kind that thought they were too good to use their power for the greater good. You were taught to never interfere with the natural order of things. To “allow nature to take its course”. Originally, you were able to hold fast to those ideals, truly believing the weight of them. But like all weight, it accumulated, growing more and more burdensome on your shoulders. As the years flew by, you felt like you could understand your brother.

Ichiro may have been a criminal, but what drove him to that point was the same exact feeling you were experiencing now. Despair. The realization that no matter how strong you may be, you are unable to control the events of life around you.

The tussle between the two of you lasted only a while longer, as you eventually succumbed to the exhaustion of your ability and the previous wounds you had gained before.

With whatever strength you had left, you had made it to Satoru’s side, grabbing ahold of his hand. Your fingers curled into his own, flinching slightly at the cold blood that graced his fingertips.

“I’m sorry I couldn’t do better.”

With that, you shut your eyes tight, hand coming up to cradle the necklace that laid across your neck. You could sense that all the sand had pooled into the bottom of the glass. Human existence was a fleeting thing, and it seemed that the sands of time had finally run out for you.

“Isn’t this a touching scene?” Sukuna's voice was back again to mock you.

“...” You had no response, no petty comment to throw his way.

“It seems you’re all out of cursed energy. I would’ve expected one more attempt from you to set things right.” He was taunting you. His sick laughter carried in the wind, the very being of it seeping into your clothes, your skin, and your soul. “If you were strong enough, all of this could’ve been avoided.”

All of this could’ve been avoided?

“I’ll do you a favor, since you’ve been so patient. It’s the least I could do.” He squatted down next to your body, knee digging into your back. In response, a sharp pain shot up your spine and into the back of your head. “I’ll give you a merciful death.”

Your hand tightened its hold around your necklace, throwing him a glare as you stared up at him. Your neck strained, a harsh breath releasing from your mouth as you croaked out your best response. “Not before… I...”

“You what?”

Your eyes slid shut as you poured every ounce of energy you had left, even if it meant a few spare minutes. “Fix everything.”

Before his hand could reach you to ultimately put an end to your life, the hourglass you held tightly in your hand shattered, and everything went black.


For a short moment, you felt at peace. Like the clouds had parted, and like giant wings, the sun wrapped around you. Reminiscent of your highschool days, you remembered your seat being directly by the window, victim to the sun if it ever chose to shine. You always had a habit of falling asleep at your desk after class, and without fail, Gojo would–

Instantly you felt hands pinching your sides, causing you to yelp and snap awake, sitting up straight in your seat and blinking your blurry eyes as you oriented yourself.

“Oyaaa! And here I thought you were gonna sleep here until morning!” Someone spoke loudly in your ear, hand coming up to ruffle your hair, the other pressing you back into the desk.

Offended, you scoffed and turned to make a snide remark, but what you saw made you freeze in your tracks. He was in his school uniform, sunglasses perched low on his nose, his bright blue irises swirling in curiosity as he awaited your response. “Satoru?”

He faltered for a moment. “Oh? We’re on a first name basis now? How naughty!”

Tears slipped down your cheeks before you could stop them. Blindly, you reached out to grab his hand and pull him to you, an attempt to hold him close. He jerked back as quickly as you came forward, limitless stopping whatever feeble contact you tried to make. Now, sobs choked out of you, unbidden, and you fell forward with your head in your hands.

“Uuuuuumm?” You felt Gojo shake your shoulders, genuine concern spreading across his face. It was a new look for him. “You okay in there?” He waved his hand in front of your pained expression, as if that would do anything to break you from your episode.

Covering your eyes, you manage to get out a quiet, “I’m fine,” but your voice broke on the second syllable. You cleared your throat. “It was just a nightmare.” A terrible, horrible, no good, very bad nightmare.

He looked serious for once. It was strange to see his teenage face making such an expression. “How about I grab Shoko?”

You shook your head. “Could you just stay here for a bit?”

You watched his feet as he hesitated, considering your words, before throwing himself down onto the chair next to you and propping his legs up on the desk. “Do you feel like talking about it?”

“Not really.” You breathed out, head leaning back to stare at the ceiling. The sun hit your face, eyes squinting shut as you felt your tears dry. You were sure that soon enough, rheum would begin to form around your eyes.

He snorted in disbelief. “Well, I had a good dream last night, wanna hear about that?”

You nodded.

“Well, last night I dreamt that me and Suguru had gone out for karaoke, BUT,” He put grave emphasis on the ‘but’. “There was a buncha guys holding up the line, and they turned out to be curses! So we had to have like– a 2 v 2 singing battle and the loser had to buy everyone taiyaki!” He slung two peace signs into the air, feet lifting slightly off the desk just to slam back down onto it. “Just so you know, I totally crushed it.” He snickered under his breath.

“Suguru definitely missed some notes, but with the power of these pipes? We took first place. And you know what they ended up buying us? Not taiyaki, that's for damn sure-! Those losers ended up stealing Suguru’s wallet and spent all of it on arcade games and gacha figurines! And not even the cool ones. You should’ve seen Suguru’s face! He looked so mad!” He giggled, hand coming down to hold his chin.

“And then we chased 'em’ down and got the wallet back, but the damage was done. So I went and bought us both hats.” He was still going. How did he remember all of this? “The only ones that were available were sun hats- like, the super girly ones with the flower and all, but I still rocked it. It was that shade of yellow that washes me out, which sucked, but my beauty can’t be hindered by something like color theory, yanno?”

You couldn’t resist huffing a laugh. “Is the only thing you talk about yourself?”

“Well, I am the best subject of any conversation.”

You rolled your eyes and turned away from him. It had always been like this when you were students together at Jujutsu Tech, arguing back and forth with the occasional competition.

If this was heaven, then this wouldn’t be so bad.

A voice startled you out of your nostalgia. “Gojo, did you complete that assignment I asked about?”

Principal Yaga?

“Yeah, yeah, I have it right here,” You watched as his pale hand reached up to pass the papers in, momentarily shocking you.

“Wait, can I see that really fast?”

“Oh, you are not cheating off of me,” he scoffed.

“Are you serious? I already turned it in, so give it here.” To be honest, you had no idea what the assignment was, you just needed confirmation.

“Whatever,” He rolled his eyes. “At least you stopped crying like a baby.”

You stuck your tongue out as you read the paper. No doubt this was an exact copy of an assignment that you had from when you were in high school. What kind of after life was this? Making you relive everything right down to every exam?

Unless–

You stood up quickly, grabbing your bag while you hit Gojo in the face with the papers, though limitless stopped you before you made contact. “I gotta go.”

“Rude?!” He gasped, exaggerating greatly as he sat up in his chair, feet swinging off of the desk.

“Oh! You’re so right– excuse me,” You turned to your teacher, a small smile forming on your face. “Yaga-sensei, I didn’t mean to interrupt. Have a good afternoon!”

“You as well, Obinata.” He sounded so young, so… carefree. Just like you remembered. Compared to the life you lived in before, this Yaga was no more, he had died by execution. Your beloved teacher, your caring principal, and your loyal friend. Just hearing your name fall from his lips was enough to calm you.

As you rushed out of the classroom, slamming the sliding door wide open, you could hear Gojo make an affronted noise. You left the room, but stepped back to peek your head around the door frame, grinning cheekily. “Bye-bye Gojo, I'll see you tomorrow. Thank you for– you know-”

Running down the hall, you could just barely hear him shout back, “Bye!”, followed by an even quieter, “she’s so weird”.The date on the paper read, “April 28th, 2006”.

12 years ago.

Time was such a fickle thing, was it not?