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When Megumi is ten, he accidentally stumbles into Gojo’s office for the first time since he moved into his apartment.
It’s not that he’s banned from entering it, or anything. Growing up around Gojo, he’s found that he simply never cared to know much about his job or what he did at that strange Jujutsu Tech school. But he’s learning to use his ten shadows technique now, which means that he’s taken his first step into the world of jujutsu sorcery. So when he finds himself standing in the doorway of the office while looking for his favourite animal puzzle, he decides, uncharacteristically spontaneously, to look around.
It is, predictably, messy. Papers are strewn all over the desk, piles of books stacked against the walls. When Megumi shifts, the sunlight coming in from the large window on the back wall illuminates layers of dust collecting on some of the shelves. As he moves about the room, stepping over little hills of binders and narrowly avoiding a random cabinet in the middle of the floor, swirls of dust kick up from the floor. Megumi winces, shakes his head, and sneezes.
The office is very Gojo, he must admit. It is messy, but there’s a certain organized chaos to its layout that feels very reminiscent of the man’s personality. If he recalls correctly, Gojo is currently out on a mission, and won’t be home in time for dinner. A glance at the digital clock on the desk tells Megumi that it’s currently 3:56PM. Plenty of time before he’ll be back.
With that in mind, he gets to exploring.
He’s curious, often, about Gojo. Just…..in general. The man who can manipulate infinity, with the universe at his fingertips. He makes it a point to bother Megumi and his sister as often as possible, always nagging them to hang out and talk, but for all his words and all the time they spend together, there’s something about him that’s always shrouded in mystery. Like there’s a part of his soul he doesn’t want anyone else to know about. He claims to be an open book, but Megumi knows better. Perhaps something in his office will provide insight - the animal puzzle he’d been looking for a few minutes ago can wait.
On the desk, right next to the digital clock and standing proudly behind the lopsided clay mug Tsumiki had made Gojo for his birthday last year, is a photograph. Megumi frowns; upon closer inspection, it appears to be a picture of the three of them, standing in front of Megumi and Tsumiki’s elementary school. Gojo is beaming like he’s just won the lottery, and Tsumiki is holding her hands up in two peace signs. Megumi, as always, looks grumpy. He remembers that day clearly, now - it was his first day of third grade, and Tsumiki’s first day of fourth. Gojo and Nanami had dropped them off together, and before Megumi could escape to the safety of his classroom, Gojo had snatched him by the back of his shirt and demanded Nanami take a photo. If he really thinks about it, he can still remember the feeling of Gojo’s hand ruffling his hair, and the sound of his voice as he made him promise to do his best in class and not get into too many fights.
Megumi isn’t sure how well he held up his side of that deal, in hindsight. He always tries his best, but kids can be mean and cruel. He isn’t sure if he has enough fingers to count how many scuffles he got into that year.
Gojo tells him constantly to mind his own strength. He has a cursed technique that he’s learning to control after all, which means he could probably demolish anyone in his year and above if he really felt like it. “Don’t be rash,” Gojo would always say as he wiped the drying blood off the back of Megumi’s knuckles after returning home from yet another meeting in the principal’s office. “Sometimes the line between protecting people and hurting them is hard to see.”
Megumi recalls the familiarity with which Gojo would say those words in particular. He never dared to prod.
Moving away from the desk, Megumi makes his way over to the shelves. Along with the huge stacks of books against the wall, there are also lines upon lines of them on his shelves. Megumi peers at their spines, sounding out the words etched into their leathery surfaces.
Unsurprisingly, they’re mostly about jujutsu sorcery: “Jujutsu Law” one of them says, followed by “Cursed Theory: A Look Into Ancient Exorcising Techniques” and “A History of Global Conflicts and Associated Curses”. Megumi’s brain whirs, the titles on the spines blurring together as his eyes scan down the lines of text that only seem to increase in content and complexity.
And then, suddenly, his eyes catch on something else: A thin, glossy yellow book that stands out amongst its peers. Physics, the spine reads.
It, unlike most of the others, isn’t leather-bound and old. It actually seems to be relatively new, Megumi concludes, as he pulls it gently off the shelf and scans its cover.
It looks…almost like a textbook. A normal, university school textbook. Fifth edition is printed in bold white letters at the bottom, and a picture of a metal ball rolling down a loopy ramp is plastered over the background. The corners of the book are almost perfectly pristine and sharp, as though it’s been sitting here since its creation. In fact, the only evidence of the book ever having been opened is the wrinkling along the front of the cover, right before it folds over the spine.
Huh, he thinks to himself. Physics. Gojo has mentioned it before, he’s pretty sure. Megumi never thought much of it until now.
He opens the book to a random page and immediately wants to close it back up. The page is covered in complicated looking equations, full of random letters and signs he’s never seen before in his life. Just looking at it all is giving him a headache. He does a quick once-over, curiously scanning the formulas to see if there’s anything he might be familiar with, and stops when his eyes reach a small subtitle highlighted at the top of the page on the right.
“I-nur-ta,” he says softly. What the hell is that?
“It’s actually pronounced inertia,” a voice pipes up from behind him, and Megumi nearly jumps out of his skin.
He whips around to see Gojo leaning against the doorframe of the office, smiling tiredly. His clothes are disheveled and he’s forgone his blindfold, which is poking limply out of his pocket. There are, shockingly, a few scratches on his face. Megumi has never seen Gojo with a scratch on his face in his entire life.
“I, uh,” he begins, “um. Uh.” He glances down at the book in his hands, then slams it shut and quickly sets it down on the lowest shelf, very much not where it had been before. “uh,” he finishes smartly.
“….Right,” Gojo says, pushing himself off the doorway and making his way over to Megumi. Slowly, he bends down, and reaches for the physics book. “Why are you reading this?” He asks, flipping idly through the pages. He doesn’t bother asking why Megumi is even in his office to begin with.
Megumi just shrugs. “It sounded cool,” he grunts, refusing to make eye contact. “Why are you back so early?”
“Finished the mission faster than expected,” Gojo replies, flexing an arm with a cocky smirk on his face. “As expected from yours truly.”
“Sure.” Megumi has to refrain from rolling his eyes. He watches as Gojo continues to flip through the pages of the physics book, pausing occasionally to read. “You into this stuff, Megumi?”
“I just wanted to see what it was about,” he grumbles. “But all the math gave me a headache.”
Gojo laughs. “Fair enough,” he says, closing the book and handing it back to Megumi. “But you know, of all the sciences, I figure physics will end up being your favourite. You do like math after all, right?”
“I guess.” Megumi stares at the book. The letters are blending together again. He frowns, and for some reason feels incredibly compelled to ask about that strange word he’d come across. He doesn’t like the feeling of knowing that there’s a concept out there that he’s entirely aware of, yet knows nothing about.
It makes him feel like he’s missing something. It’s weird. So, shifting uneasily from foot to foot, he asks, “what is inertia?”
Gojo blinks at him. “You really wanna know?” He asks. He sounds genuinely surprised.
“I wouldn’t ask if I didn’t want to know.”
“Huh,” Gojo says, then laughs. “Yeah, I suppose that’s true.”
Without saying anything else, he reaches for the book and opens it instantly to the same page as before. “Inertia,” he begins, pointing to the word on the paper. “It’s a property of motion. You ever heard of Isaac Newton?”
“Yes,” Megumi says. He’d learned all about him in a history class a few weeks ago. His teacher posted a picture of the man on the large chalkboard at the back of the classroom for everyone to look at later, and Megumi distinctly recalls thinking to himself that his hair looked really funny. It was comically and unnecessarily big, styled into large, bouncy curls that framed the sides of his very serious face.
“Well,” Gojo continues, and Megumi snaps back to reality. “Newton was a pretty smart guy. He came up with three laws to define motion - the first was about inertia. He stated that an object at rest, or an object in motion will continue that motion unless acted upon by another force.” To demonstrate, Gojo lifts one of his hands and moves it horizontally, then uses his other hand to block its path. “See?”
“I guess,” Megumi mutters. “Seems pretty simple to me.”
Gojo guffaws. “Sure, for now,” he says breezily. “It’s all fun and games until you have to apply that law to a bunch of formulas. It won’t be so simple then, trust me.”
“But it feels so obvious,” Megumi argues. “Of course an object will keep moving unless something else stops it. What’s so revolutionary about that?”
“Everything,” Gojo replies. His smile softens, and he reaches for the book again to pull it out of Megumi’s hands. “Life is complicated, buddy,” he says, placing the book back on the shelf. “Sometimes it feels like it’s moving so fast we forget the most simple things. Sometimes it gets so complicated we blame strange situations on otherworldly phenomena. Sometimes things get so bleak we feel like we’ve lost control of everything.” He bumps Megumi in the chest softly, right over his heart. “It’s good to remember that there are some rules we can always rely on - that an object in motion, no matter where it’s headed and no matter how fast, can change its course so long as something else has the drive to push it that way.”
Megumi stares at him. Ponders. Feels the reverberations of Gojo’s fist hitting his chest, listens to the sound of his words echoing in his ears.
Casually, his world shifts. He feels weightless, suddenly, like the galaxy is changing around him.
“Megumi?” Gojo says, after a few minutes of silence have passed between them. “You okay?”
“Yeah,” he replies quietly. It hits him suddenly that he’d been staring at the physics book. “Inertia sounds pretty cool,” he says simply, finding his words.
“It is,” Gojo agrees, and rises with an exaggerated noise of effort. “Alright, enough science for now. Time to make dinner. What are you feeling today?”
Later that night in the kitchen, after they’ve argued about what to eat and stressed Tsumiki out with dicing the vegetables, Megumi and Gojo sit at the dinner table, nursing hot cups of tea. Tsumiki had gone to bed after eating, claiming she had an early morning the next day for a school club activity.
“I think I like physics,” Megumi says suddenly, and Gojo turns to look at him, his eyebrows raised. “Yeah?” He says, questioning.
“Yeah,” Megumi confirms. “I think I like knowing what to rely on. I like knowing that the things that don’t change can help us understand the things that do. I like knowing….that there are things that I just know.”
“Very insightful,” Gojo titters. “And what are the things that you just know?”
Megumi pauses to think about it. Sees flashes of forced visits and outings, of food on the table and warm running water in the winters. He thinks of a familiar smile, of how different his life is now than it had been five years ago.
“I know that bell peppers are yucky,” he begins. “I know that reading is fun. I know that dogs make the best pets.” He hesitates for a moment, then takes a small sip of his tea. “And…I know that you’re here.”
Every damn time.
Gojo puffs out a surprised breath at that, then reaches over to ruffle his hair with a smile that’s somehow as loud as it is wide. “That’s true,” he says, taking his own sip of tea. “That is very true indeed.”
***
When Megumi is fifteen, he takes his first physics test.
He finishes the whole thing in one hour. Gojo flips through the pages, grading his work as Megumi relaxes on the floor in the doorway, relishing the warm summer breeze.
“Good work,” Gojo says after a while. He stands from behind the desk he’d been sitting at, and hands Megumi his test back. A bold 100 is scribbled at the top in bright red ink. “Quick, too.”
“Yeah,” Megumi says. “I just know physics, I guess.”
“Hm,” Gojo hums. “Wanna get dinner tonight to celebrate? Well - for you to celebrate, at least. Not sure how Nobara and Yuji will do.”
Megumi contemplates the offer for a moment. “Sure,” he decides. “Where?”
“How about sushi?” Gojo grins, looking mischievous. “The place next to that kikufuku stand.”
“Of course you’d want to go there,” Megumi grumbles, pushing himself to his feet to level Gojo with a hard stare.
The man snorts, then tilts his head to the side. “Smarty pants,” he teases playfully. “How’d you know that’s what I was going to suggest?”
Megumi shrugs, his gaze trailing over the first page of the test in his hands. The third question, part of the short answer section, catches his eye. Define inertia, it says.
With a sigh, he hands the test back to Gojo and turns to step out of the room. “I just know you,” he says simply, and behind him, Gojo laughs.