Chapter Text
"Did you really have to text me at three in the morning?" Megumi muttered, shoving his hands deeper into his pockets as he trudged up the cracked sidewalk. The afternoon sun did little to warm the autumn chill, and his breath curled faintly in the air.
Itadori's reply came muffled through the door before he even knocked. "Yes! Because I need someone to suffer with me!" The door swung open, revealing Itadori's grinning face, slightly flushed, as if he'd just sprinted to answer. His hair was messier than usual, sticking up in odd directions, and his uniform shirt was wrinkled—home early from school, then.
Megumi stepped inside, toeing off his shoes without bothering to untie them. The house smelled like burnt toast and something faintly herbal—incense, maybe. It was quieter than he expected. "Where's your uncle?"
Itadori flopped onto the couch, sprawling like a starfish. "Out back. Said he was gonna 'enjoy the weather' or whatever that means." He waved a hand vaguely toward the sliding door, where the silhouette of a much taller figure was just visible through the frosted glass.
Megumi’s pulse stuttered at the sight of Sukuna’s silhouette—broad-shouldered, unmistakable—through the frosted glass. He swallowed, fingers twitching at his sides before he forced them still.
"Right," he said, too quickly, and turned back to Itadori, who was now digging through a half-collapsed pile of manga on the coffee table. "What exactly did you need me for, anyway?"
Itadori didn’t look up. "Oh! Yeah, so—" He unearthed a crumpled worksheet, the edges torn where he’d clearly ripped it from a notebook in haste. "I kinda forgot we had a calculus test tomorrow."
Megumi stared. "You texted me at three AM for homework?"
Megumi pinched the bridge of his nose. "You're unbelievable."
Itadori grinned, completely unrepentant, and thrust the worksheet toward him. "C'mon, you're the only one who actually gets this stuff. Tsumiki said you aced calc last year."
Behind them, the sliding door rattled open. Megumi didn't have to turn to know who it was—the shift in the air, the way Itadori's posture straightened slightly, the sudden warmth at his back. Sukuna's voice rolled over them, deep and amused. "Trouble in paradise?"
"Uncle!" Itadori waved the paper like a white flag. "Megumi's gonna help me not fail!"
Megumi's throat went dry as Sukuna stepped into the room, the sliding door clicking shut behind him. The man moved with the ease of someone who owned every space he entered—shoulders loose, hands tucked into the pockets of his dark sweatpants. The hem of his shirt rode up just slightly as he stretched, revealing a sliver of tattooed skin that made Megumi's fingers itch to trace.
"Calculus, huh?" Sukuna mused, plucking the worksheet from Itadori's grip with two fingers. His eyes flicked over the crumpled paper, then up to Megumi, who stiffened under the attention. "Guess you drew the short straw, kid."
"Don't call me that," Megumi muttered automatically, though the protest lacked bite. He could feel the heat creeping up his neck. Sukuna only smirked, tossing the worksheet back onto the coffee table where it slid into Itadori's lap.
"You're lucky he showed up at all," Sukuna said, ruffling Itadori's hair roughly enough to make him squawk. "Three AM texts deserve curses, not tutors."Megumi exhaled sharply through his nose, trying to ignore the way Sukuna’s presence filled the room—like a storm front pressing against his skin. He snatched the worksheet from Itadori’s lap, avoiding eye contact. "Let’s just get this over with."
Itadori, oblivious, bounced off the couch and grabbed Megumi’s wrist, dragging him toward the kotatsu. "You’re the best! I’ll get snacks!" He vanished into the kitchen, leaving Megumi alone with Sukuna, who hadn’t moved. The older man leaned against the doorframe, arms crossed, watching him with an expression that made Megumi’s stomach twist.
"You’re blushing," Sukuna observed, voice low.
Megumi’s head jerked up. "It’s warm in here."
Sukuna chuckled, the sound vibrating through the room like a struck chord. "Sure it is." He pushed off the doorframe, moving closer in that slow, deliberate way of his—like he had all the time in the world.
Megumi clenched his jaw, willing himself not to retreat as Sukuna reached past him to pluck a stray manga off the kotatsu. His forearm brushed Megumi's shoulder, and the contact sent a jolt down his spine.
"Trig substitution," Sukuna remarked, flipping the worksheet between his fingers without looking at it. "You’re good at that, aren’t you?" His gaze lingered on Megumi’s face, heavy with something unreadable.
Megumi swallowed. "I—yeah. It’s not hard."
Sukuna hummed, leaning in just enough that Megumi caught the faint scent of cedar and something darker beneath—smoke, maybe. "Cute," he murmured, so quiet Megumi almost thought he imagined it.
Itadori chose that exact moment to barrel back into the room, arms laden with chips and soda cans, his socked feet skidding on the hardwood. "Snack attack!" he announced, dumping everything onto the kotatsu with a clatter.
The sudden noise shattered the tension like glass—Megumi jerked back, nearly knocking over a can of Pocari Sweat, while Sukuna merely arched an eyebrow and straightened with infuriating ease.
"You're gonna give him a heart attack," Sukuna said, plucking a chip from the bag Itadori had torn open. He popped it into his mouth, gaze sliding back to Megumi, who was now glaring at the worksheet as if it had personally offended him.
"Shut up," Megumi muttered, snatching a pencil from Itadori’s haphazardly strewn school supplies. He stabbed it against the paper, focusing on the equations like they held the secrets of the universe. Anything to avoid looking up and meeting that smug, knowing stare.
Itadori flopped onto the cushion beside him, crunching loudly. "Okay, so explain it like I’m five," he said, mouth half-full.Megumi exhaled sharply through his nose, tapping the pencil against the worksheet harder than necessary. "First, stop talking with your mouth full. Second, you're seventeen—act like it."
Itadori swallowed loudly and grinned, wiping crumbs off his chin with the back of his hand. "But calculus makes me feel five."
Behind them, Sukuna chuckled, low and warm, and Megumi stiffened as the man's shadow stretched over the kotatsu. He didn't turn around, but he could feel Sukuna leaning over his shoulder, close enough that his breath ghosted over Megumi's ear. "Kid's hopeless," Sukuna murmured, the words curling around Megumi like smoke. "Better make it simple."
Megumi's grip on the pencil tightened. "I am," he gritted out, resisting the urge to elbow Sukuna in the ribs—partly because it wouldn't faze him, partly because the idea of touching him on purpose sent a traitorous heat crawling up his neck.
Megumi dragged a hand down his face, exhaling through clenched teeth as Itadori blinked at him with exaggerated innocence. The worksheet between them might as well have been written in hieroglyphics for all the progress they were making. Sukuna’s presence loomed behind him, a living furnace of heat and quiet amusement that made the back of Megumi’s neck prickle.
"Okay," Megumi muttered, tapping the pencil against a particularly mangled equation. "Let’s start with the basics. You do remember what a derivative is, right?"
Itadori’s grin faltered. "...The slope thing?"
Sukuna snorted. Megumi didn’t turn, but he could *feel* the man’s smirk like a physical weight between his shoulder blades.
Megumi resisted the urge to slam his forehead against the kotatsu. "The slope thing," he repeated flatly. "Yes, Itadori. The slope thing." He jabbed the pencil at the first problem. "So if we're finding the derivative of this function—"
"Wait, wait!" Itadori scrambled for his notebook, flipping pages until he found one that wasn't completely covered in doodles of questionable quality. "Okay, go slow."
Behind them, Sukuna shifted, the floorboards creaking under his weight. Megumi could hear the smirk in his voice before he even spoke. "Might wanna break out the crayons for this one."
Megumi's jaw clenched. "Don't help."Megumi didn't realize he'd been holding his breath until Sukuna's footsteps retreated toward the kitchen, the weight of his presence lifting like fog burned away by sunlight. Itadori, oblivious to the way Megumi's shoulders sagged in relief, tapped his pencil against the kotatsu impatiently.
"So like," Itadori said, squinting at the paper, "if the slope thing is how steep it is, does that mean—"
"God, no," Megumi cut in, dragging a hand through his hair. He could hear Sukuna rummaging through cabinets, the clink of glassware a counterpoint to Itadori's mounting confusion. "Just—here." He snatched Itadori's notebook and scrawled a crude graph. "This is the function. The derivative is the slope at every point on this curve. You're not calculating one number, you're—"
A cold can of soda pressed against the back of his neck. Megumi yelped, nearly upending the kotatsu as he whipped around to find Sukuna looming over him, grinning like a predator who'd cornered his prey. "Thirsty?" Sukuna rumbled, shaking the condensation off his fingers deliberately, droplets catching in Megumi's hair.