A/N

Ayo, yet another SI-OC after reading Jujutsu Kaisen and realizing 'huh, I need a self-insert fic for this'. This would be pre-canon (if you haven't seen the tag) and things. I would like to keep this short since I'm writing other fics. Plus, JJK is still ongoing so this will have extreme canon divergence.

Edit: Extended the fic to more than 10 chapters with longer coverage. Changed some of the dates for consistency. Corrected some grammatical mistakes (7/?)

Beta-reader: Biabialex

1996 April 05

Tokunaga Emi had no mother.

Not in a way that her father knew. Of course, that was because the woman died. She only gave birth to her and had left her under her father's care majority of the time. They had to mourn for her a year ago when she lost her life asleep. In truth, Emi had no attachment to the woman, not because she was distant but because she had a suspicious stitched scar on her forehead.

Unlike normal children, her brain already developed right after birth. Furthermore, her senses were extremely sensitive, allowing her to observe her surroundings. Not to mention the memory of a previous life Tokunaga Emi had never lived occupied the majority of her brain.

In that memory, she was a medical practitioner—a doctor, specifically. That was until she died at the age of 35 due to overwork. It was not a death she was proud of, but she had to make do.

The 'her' back then was orphaned right after birth and was adopted by a wealthy couple that could not give birth to children. They were good to her, and she was indebted to them. As a result, she strived to do better, made accomplishments, and prove that she could achieve anything using her own hands. Soon, that mindset took a toll on her, the countless sleepless nights started to lower her immunity, and ultimately, it led to sickness and death.

Much to her chagrin, she found herself being tortured in the womb by none other than Kenjaku himself—the main antagonist in the manga she had read before, Jujutsu Kaisen (呪術廻戦).

Emi did not hold any grudges, although being mothered by a psychopath did not occur in her wildest dreams. Kenjaku was known as the ancient jujutsu sorcerer who wanted to 'evolve' humanity via natural selection. He would steal bodies—dead or alive—using his cursed technique and occupy it, letting him live for at least a thousand years. By removing non-sorcerers, sorcerers could reproduce between themselves, birthing people like them. The girl knew this plan had a significant flaw—the population of people who could use jujutsu were far less than those who could not.

And if Kenjaku attended his biology class, he would know this process would take a long time. Not to mention if humanity were still alive after a million years, the numbers of cursed spirits would decrease seeing the large population of sorcerers. As a result, it would also lower the quality of sorcerers; each generation would have lower cursed energy than the next.

That led to, again , lower numbers of jujutsu sorcerers. It was a futile attempt causing the needless death of billions of lives.

Glancing at her reflection in the mirror, Emi felt wonder as her gaze landed on the white patch of hair on her forehead. She guessed it was a good thing that she inherited the genes of Kenjaku's host. It was her first time having such a notable physical trait. The girl felt terrible, realizing the woman must have died before the ancient sorcerer stole her body, and now he was sullying her corpse.

Tokunaga Emi realized she might as well forget about her conjectures. Now, the only thing she was looking forward to was the birth of her brother, Itadori Yuji.

1997 August 17

Emi could see cursed spirits (呪霊, Juri) right after she was born.

They were hideous, considering they were born from human's negative emotions. They would hover around her when she was a child, and she would see them in every part of the house. It did not help that her father was scared silly by strange events caused by curses which gave Kenjaku a free rein on what to do with her. By the time of her mother's death after she was given to her father, the curses disappeared.

Jujutsu historians said that cursed spirits were created from the build-up of negative human emotions. As noted from the Jujutsu Kaisen series, the hot spots would usually be schools and hospitals where resentment resided. Looking back, perhaps the rare situations in medieval ages created more curses seeing mass hysteria's semi-frequent occurrence.

Witch trials were also a thing, and assuming they were sorcerers, there would be less people who would be willing to exorcise publicly. It was probably why there were more cursed spirits as well.

Tokunaga Emi was not fond of history, but she found that part interesting. It did help her interests that the library around their home would place the history and science sections together because of the lack of books. After a while, studying became her hobby, and with no source of entertainment, she could only extend her interest to other subjects.

It was a good thing she manifested her cursed technique earlier, allowing her to experiment with it during her free time. Emi's father would be at work most of the day, and her aunt from across the street would check on her from time to time. She would usually be alone at home thanks to her aunt's unconditional trust because of her more than average intellect.

Honestly, it annoyed her how her body could not handle her adult brain. Overthinking made her sleepy, and playing with her technique would tire the shit out of her.

Emi's inner technique (生得術式 Shōtoku Jutsushiki) was vibration. At first, she could produce vibrations from her hand, and the longer she practiced it, it eventually extended to her other body parts. On the other hand, the distance covered would depend on her mental strength, and for now, she could move objects for a few meters. Frankly, the word 'vibration' summarized it, but if she gave a further explanation, it would be the technique to move the particles of an object.

This might also happen in the air, although she had not tried it yet.

The only downside was it was hard to control. It would produce loud sounds that attract unwanted attention. But if the vibration was good enough and the frequency was just right, the girl could break a glass or two, no biggie, which had gotten her into trouble quite a few times after her father saw the glass shards in the trash can. It did not help that he became suspicious a few days before when he watched his favorite TV show realizing he lost his treasured mug.

Crash!

Tokunaga Emi felt a sudden dread as she watched the glass of water fall from the table.

The girl was lost in thought, forgetting her father placed the cup on top of the wooden table in a hurry before he went to work when she applied her technique. Emi frowned, imagining the scolding she would get if her father learned another ceramic lost a battle against her. She quickly thought of hiding the glass shards somewhere in the house when she remembered her aunt would usually dig a pit in her backyard as compost.

That would be a good hiding place .

Emi sighed tiredly as she grabbed some newspapers and a towel to clean the crime scene.

1998 March 02

They never celebrated Emi's birthday ostentatiously. Instead, her father preferred it lowkey.

For her eight birthday, the man decided to let her visit her grandfather in his hometown. Emi was far from excited after recalling her father's monologue about his parents. They tended to have traditionalist views, and upon learning that their only son would prefer living in the city, they promptly cut off all communications with him in disappointment. It was recently rekindled with the death of their daughter-in-law when her father decided to open up the option of letting her live with her grandfather in case his work got hectic.

The trip was exhausting; she had let herself sleep on her father's lap quite a few times. Emi woke up mostly groggy and disoriented. The vibrations of the train as it traveled to the tracks did not help her nausea. Her senses were extremely sensitive, particularly with anything connected to vibrations. She never thought she would hate this ride more than being thrown in the air in a bungee jump in her previous life.

Nevertheless, they arrived at their destination after a few hours.

Emi had to rush to the restroom and vomit her morning meal in the toilet. She made a lot of mess and needed the help of a woman passing by to clean it up. The poor lady must have heard her wrenching in pain inside the cubicle. It also hurt her throat from the acid passing through her throat. The little girl apologetically bowed to the woman and left the place hastily to meet with her father.

The man gave her a concerned look then patted her head. "Are you okay, gaki?"

"I'm quite there." Emi coughed a few times to relieve the itchiness in her throat. "Are we still far from Ojiisan's place?"

"We're near." Her father squatted in front of her and held her chin. "Open up your mouth and let me see."

The now eight-year-old girl obediently followed the man's instruction and opened her mouth with 'aah's.

"It's alright," he muttered under his breath and stood up. "Next time, I'll take into consideration other commute options."

Emi hummed in agreement as she observed the station in wonder. It was the same as she had seen in pictures, and she was pretty glad the place was clean. Their family could never own a car just by her father's salary. They were also paying a large loan from buying the house beside her aunt's place. Although the price was considerably low compared to the future, for their current state of living, it was something her father needed to work hard for.

They reached her grandfather's house after taking the taxi. As the house came into view, she could see that they traditionally built the place. It was made using wooden columns, and the floor was elevated. Upon entering, they removed their shoes as her father called out to the people inside. The air was cold, and unlike the city, it was fresher, making it easier to breathe. A woman, smaller than her father, welcomed them and introduced herself as the house's caretaker.

"You're here, Koichi-san. And this is?" The woman acknowledged their presence then looked at her.

"Ah, this is Emi-chan. Emi-chan, say hi." Her father pushed her forward, making a fool of herself after she scrambled her footsteps.

The little girl bowed respectfully, a little flustered. "Hi, I'm Tokunaga Emi."

"Then welcome, Emi-chan." The woman looked at her, amusement in her eyes as she watched her face reddened while making the little bow. "Tadashi-san is in the living room. You can meet him there."

Her father nodded as thanks and entered the house, Emi following behind him. An older man was sitting on top of the tatami mat, seated in a seiza position. He appeared to be in his mid-60s with a head of white hair; he was wearing a hakama over his black kimono. Her grandfather did not smile upon seeing them; he only grunted and motioned for them to sit.

Emi felt their presence was unwelcomed but followed suit when her father sat on the floor nonetheless.

"It's nice to see my granddaughter after all these years, Koichi." The old man's expression was anything but 'nice' as his gaze landed on the little girl, examining her. A trace of surprise appeared in his eyes as he placed the tea he was drinking back on the table. "How old is she this year?"

"She turned eight today," Koichi replied, confusion evident on his face because of the sudden change of his father's mood.

The old man narrowed his eyes and showed a not-quite-smile. "That's good."

The conversation got back to where it was, and her father was forced to tell the old man about his deceased wife. Maybe it was because both of their wives passed away, but her grandfather seemed to treat them better now.

Emi's grandmother died when her father was in high school. She did not know how or when exactly it happened, but it somehow destroyed the relationship between Tadashi and his children. It did not help that Koichi decided to stay in the city to join his sister instead of staying in their old home to inherit and take care of their land.

The little girl knew her father's personality; he was a free spirit, and his skills, along with his young age, had gained him a foothold in his job. It was not something he could leave on a whim, especially after having a child. Nevertheless, he still valued familial relationships considering he never left her even after the curses surrounded her mom.

Their conversation ended before evening. Emi's grandfather decided to withdraw to his room and eat there while Emi and Koichi stayed in the living room as the caretaker served their dinner. The room was quiet, and the girl could hear only the sound of eating. The girl's eyes wandered around the room and saw a black blob covered with eyes floating at the corner.

Emi mentally noted to exorcise the curse after everyone fell asleep.

1998 March 04

Tadashi seemed to be fond of the little girl.

Emi did not know why but after backtracking, it seemed to have started when she exorcised the cursed spirit inside the house. It was the third day of their stay, and they had to leave by the fifth. Usually, she would be by Koichi's side, following him wherever he went, but today he would meet with his high school friends. She was not allowed to come.

Not that her father forbade it, but it would be a hassle to bring a child when adults were talking, and Emi knew that.

Her grandfather took her out today, Emi holding his hand. They went to the town's playground. There were quite a few children her age, and none had guardians present to look after them. Emi did not mind it. Maybe the children in this town were highly independent, unlike those in the city. No, she was not saying she was not independent, but it was easier to get a rise out of city kids from what she had seen so far.

The playground had a lot of equipment, and she could hear sounds of laughter from afar. Tadashi let go of her hand and faced her when they reached the nearby bench. He carried and placed her on top of the seat, letting him look at her at the same eye level. Emi quietly obliged to her grandfather's whim as she looked at him with a blank face.

"You really remind me of your Obaasan." Tadashi held her face in his hands, delight apparent in his voice, coupled with his angry-looking eyes; it was quite a sight.

"Ejiichan, ere ye genna leave me her?" Emi murmured, irritated when the older man pinched both of her cheeks. (Ojiichan, are you going to leave me here?)

Tadashi let her cheeks go then she sighed in relief. "That's the sign of my affection. You're not allowed to dislike it—" he flicked her forehead and placed his hands on his hips, "—and yes, I have to leave you here since I have something to do."

"Okay," she replied softly and jumped down from the bench.

Emi watched her grandfather walk away then directed her gaze on the playing children. She resolved herself to stay on the bench, unwilling to play with kids mentally younger than her. The girl was not good with kids even when she became older; she never wanted a child for herself. Now, if she dived headfirst into their group, she would feel accountable if something terrible happened to them and she refused to act as their nanny.

The little girl decided to practice her cursed technique to pass the time. At present, her range significantly increased as well as her control. It became less difficult to manipulate molecules as she used it daily to practice. Emi's range could be a kilometer at most if she put her mind to what she was doing. It took her a couple of trial and errors to test it in passing low-level curses in their neighborhood before she could use it to exorcise. Thankfully, ordinary people could not see them, or else Koichi would have caught her a long time ago.

Emi ran a hand through her black hair and hoped time would pass quickly.

1998 March 05

Satoru Gojo, to say the least, was an honest child.

That was why when he saw the girl who had the same amount of cursed energy as him on the playground, he went to her directly for a confrontation. He was not the type to create a fight, but he had been staring at the little girl for two days now, and she had yet to acknowledge his presence. Satoru was curious about the person as well, considering she had ignored his rude gaze.

But to his surprise, the girl—Emi—was unlike anyone he had seen before. When he came up to ask about her sudden appearance in the neighborhood, the girl shrugged, telling him they were just there to celebrate her eight birthday. The white-haired boy was a little astonished that she was just a few months younger than him.

The boy stared at the girl's prominent white patch of hair on her forehead, wondering where she inherited it from.

"Wow, I never realized it felt good to look down on you." Emi looked impressed at herself after comparing their height difference. The future strongest jujutsu sorcerer wanted to smack the girl on the face but held back.

"That's because I still have time to grow, smartass." The white-haired boy kicked the stone in front of him in a bad mood as he tried to keep his composure. He had forgotten the reason he approached her in the first place after the girl boasted.

Emi could not help but smirk when she realized she had damaged the boy's pride. "That's still in the future. What's important is that I'm taller than you now ."

Satoru scowled, then glared at her sharply, ignoring her comment. No one had ever dared to disrespect him as the girl did. He was born with six eyes ( 六眼 ), allowing him to master his inherited technique limitless ( 無下限) at its fullest. The boy was the first sorcerer to utilize his immense cursed energy for the last four hundred years. As a result, he was treated with reverence and care. It made him highly arrogant and would only treat people who he deemed strong enough with respect.

The pressure he was carrying was immense, taking into account the future of the Gojo family. Frankly, this was the first time he was treated like the child he is. Satoru felt overwhelmed and became speechless. After exchanging banters with the girl, he got to know she was brought up as a civilian.

"You should make the entrance of the sandcastle on the other side." The girl ordered him as she pointed at the place he was standing.

"…why do I have to do this?" Satoru frowned in annoyance but obediently agreed with her request nevertheless. "This is for children!"

"You are a child. Plus," she skillfully manipulated the sand using what he thought was her cursed technique and continued, "There is no age limit to having fun."

The white-haired boy sighed in frustration and decided not to reply. He could process and analyze information at an inhuman speed; even if he were not observing Emi, he could still see her movement from the corners of his eyes. Satoru got to know what type of child she was, and unlike children from a Sorcerer's family, the girl was more free-spirited and unbridled.

Both children 'played' for a few hours until Emi's grandfather appeared to get her. The girl only waved her hand goodbye then proceeded to run to her guardian. Satoru watched her fading figure as tiredness washed over him. Doing typical tasks made him feel it was way out of his league, but he handled the situation pretty well, to his amazement.

A man appeared behind him. "Satoru-sama," he respectfully called.

"Let's go home." Satoru blinked and turned to the man silently. He compared his aide's level of cursed energy to Emi's, and as he expected, the girl was like him.

The white-haired boy walked home, coming to a realization. Playing with sand was not as bad as he initially thought.

1998 March 06

Emi pouted when her father told her she would need to stay in her grandfather's home. Koichi had to travel far to catch up with his work, and her aunt could not take care of her because they had to move. Tadashi was more than willing to be her temporary guardian for as long as his son wanted, so on the fifth day of their stay, she bid her farewell to her father.

The girl was not complaining, and although she got to spend more time with the Gojo Satoru, the child stressed her seeing he was way more self-absorbed than she originally thought. The only good thing was he was not much of a brat, and he could take her jokes with a grain of salt. The boy was far from his manga persona as an adult, putting up with it was a chore.

Surprisingly, she could feel Satoru's cursed energy, and they had more or less the same amount. What amazed her was the child's genius, she had seen him use his technique here and there when they were playing (using cursed energy to make sandcastles was neat , by the way), and he had perfect control over it. Meanwhile, she had to destroy many things just to have a basic understanding of her skill.

Emi wished she was born with talent rather than having unsolicited perseverance. Seeing someone getting what you worked hard for truly made her jealous.

Nevertheless, when Tadashi asked her if she wanted to visit the playground again, she said yes. It was an opportunity to steal some skills from the future strongest jujutsu sorcerer, she would never say no to that. Furthermore, the boy did not dislike her curious nature; he was more than willing to answer her questions about cursed energy.

"So infinity , huh," she said, amazed as she watched her index finger hover above the boy's hand. "So you recently discovered that?"

"Not long ago. I need to add a few things, but there was nothing I could think of for the moment." Satoru confirmed as he deactivated his technique.

Emi closed her left eye for a moment, trying to think about what she remembered in the manga. "It's good if you can apply it at all times."

"That's not possible…at the moment." The boy commented, unsure as he retracted his hand and squatted down to continue playing with the sandcastle they made.

"Is it really okay for you to tell me those things?" Emi asked while wearing a confused expression. "From what you told me, that is restricted information."

"Most of the things I told you are already known in the jujutsu community. Moreover, what can you do to me? You're just a civilian a few days ago."

Emi rolled her eyes, then corrected him, "I'm still a civilian."

"Not anymore. I asked my father if I could bring you home so you could join me while I train." Satoru commented matter-of-factly, to which the girl gave him a horrified expression.

" No way , tell me you're just joking." The little girl felt a chill run on her spine, foreboding something troublesome would soon come her way.

The white-haired boy smirked and glanced at her faux-importantly. "I'm doing this for your sake since you have a large amount of cursed energy. It would be helpful for you to learn how to exorcise curses properly."

"My Ojiichan would never allow me," she hastily found an excuse as she frowned.

"He already agreed."

"What ?! When?" Emi shouted, panic evident in her voice. "Why would a civilian agree to that?"

The white-haired boy glanced her way, a little amused as he flicked her forehead. "Tone it down, stupid," he warned her, while recalling the recent events then added, "he was a retired jujutsu sorcerer under the Gojo family; sadly, none of his children had above-average cursed energy."

Tokunaga Tadashi was a civilian turned jujutsu sorcerer after the Gojo family took him under their wing. He then became the aide of Satoru's grandfather for decades, even until he wedded a non-sorcerer. Eventually, he retired, returning to civilian life after learning that none of his children could inherit his cursed technique.

Emi realized that was probably the main reason he was disappointed at his only son, Koichi. The girl felt it was unfair that the older man mistreated his son for something he could not control. It must also be the reason why Tadashi gave her his sudden affection, figuring out she exorcised the cursed spirit in the living room on the first day they met.

"This is troublesome." The little girl could not help but complain as she blew the loose white hair strands away from her face.

Satoru saw her attempt to be unsuccessful, so he tucked her hair behind her ear. The girl muttered a word of thanks at his action while frustratingly destroying the sandcastles they created earlier.

Emi was never the type to volunteer and save people. She would only help those who she wanted to save. It was a weird mindset considering she was a former doctor, but in her line of work, you needed to know the extent of how far you could help. The girl could not have a weak resolution, or else she had lost her mind a long time ago considering the patients she failed to save.

"I figured out you were lazy, but not to the point you would refuse training with me." The white-haired boy dusted his clothes, the tiredness from the six-eyes kicking in suddenly.

"Who are you, Kami-sama? Excuse me, Satoru-kun—" she sarcastically drawled, emphasizing the suffix 'kun,' "—you're not that special."

"You've made that pretty clear for the past two days." The boy closed his eyes then sighed, sitting down on the sand. He used his hand as support while he leaned on the girl.

"I took it upon myself to bring you down a notch."

"Isn't that additional work?"

"—wait , damn. You're right."

Tadashi picked up the miso bowl on the table then handed it over to his granddaughter. "You know it's hard to act normal when you can see curses left and right. You should serve Satoru-sama like what I did to his grandfather, Kunitaro-sama."

Pretending he did not see the little girl grimace, he continued to eat his dinner. The old man had seen the young master and Emi interact amiably on the first day. He did something any good grandfather would do for their granddaughter—he went back to the Gojo family compound to meet with his former master and friend. Tadashi requested them to take care of the girl's needs as a young sorcerer since he alone was not enough, bearing in mind his old age. Although he still had above-average strength, he could not compare it to her granddaughter's potential in the future.

"Ojiichan, I want to stay with my father. You know he only has me." Emi had seen his father struggle to give her a better life. After her mother's death, he did not hesitate to go back to work so that he could put food on the table.

Tadashi sighed, utterly aware of their circumstance but still refused to give in. "You have a large amount of cursed energy; even if you don't go and bother curses, they will bother you. The only way for you to completely control them is by practicing."

In truth, the older man was wondering where the girl had gotten that large amount of energy. He did not have that power when he was young, and neither did his son. The only person he could think of was the child's mother, who he had never met. He needed to talk to Koichi soon about her daughter-in-law. Her death might not be simple, and they might be affected.

Granted, there was only a small chance the woman might be using her cursed energy wickedly—like a curse user (呪詛師, Just-shi). But there was a nagging feeling at the back of his head that this was something he could not overlook.

"Why did you try and live a normal life, Ojii-san?" Emi asked after they finished eating, putting her chopsticks at the top of her bowl.

"When you have a family, you'll know," he nonchalantly answered after drinking a glass of water. "I could not put your Obachan and your Tousan in danger by continuing that line of work."

Tadashi conveniently omitted that he might also lose his life in the process, leaving his children parentless. Contrary to the belief of others, he did not hate his children. He was saddened that he would need to give up something he had been doing for a long time. The old man never regretted choosing his family over being a jujutsu sorcerer, although his granddaughter did make him on cloud nine.

Emi did not seem to want to ask other questions as she obediently sat opposite of him. The dinner finished when he called the caretaker to clean the table. Tadashi ushered the little girl to her room then went to his own to rest like he always did.

The little girl's questions brought back unwanted memories from before. His wife died after he failed to save her from a cursed spirit with consciousness, and on top of that, he was unable to capture it when it tried to escape. That was his only regret; he hated curses with his entire being and would go back to his previous occupation if he had the chance. But he had to think of his granddaughter now and how he needed to set a good example.

Tadashi was not getting any younger, and if he did not raise her as a good jujutsu sorcerer, it would be one of his lifelong guilt.