Archive of Our Own ^beta

Chapter Text

“Lashes~!” The blonde-haired man practically danced into the office, his voice lilting in that sing-song cadence that never failed to grate on everyone’s nerves. His bright pink sneakers squeaked against the polished floor, and his grin was so wide it looked almost cartoonish, as if he’d just stumbled upon some grand, mischievous secret.

Sae, slouched at his desk with a mountain of paperwork threatening to topple over, didn’t even bother looking up. His pen scratched furiously across the page, the only sound in the room besides the intruder’s obnoxious humming. The dim glow of the desk lamp cast sharp shadows across his face, highlighting the faint crease of irritation between his brows.

“What do you want, Shidou?” Sae’s voice was a low, exasperated growl, each word dripping with the exhaustion of someone who’d dealt with this particular nuisance far too many times.

Shidou, undeterred, twirled a lock of his messy blonde hair around his finger and leaned dramatically against the edge of Sae’s desk, knocking a stray pen to the floor. “Oh, Sae-kun, don’t be so cold~!” he chirped, his tone teasing as he waved a sealed envelope in the air like a prized trophy. “Ness asked me to deliver this little love letter straight from headquarters. New mission~!”

Sae’s pen froze mid-sentence. He finally lifted his gaze, his sharp green eyes narrowing at the envelope as if it personally offended him. “A mission?” he repeated, his voice flat but laced with suspicion. “And they sent you to deliver it? What, did they run out of carrier pigeons?”

The demon gasped, clutching his chest in mock offense. “So mean! I’m hurt, Sae, truly wounded!” He flopped into the chair across from Sae’s desk, one leg swinging over the armrest as he tore open the envelope with exaggerated flair. “But since I’m such a kind soul, I’ll forgive you. Wanna hear the juicy details, or are you gonna keep brooding like some tragic anime protagonist?”

The Itoshi only pinched the bridge of his nose, already regretting the next ten minutes of his life. “Just read it, Shidou. And stop talking like you’re auditioning for a musical.”

With a dramatic flourish, Shidou cleared his throat and began to read, his voice shifting to an overly theatrical tone as if narrating an epic tale. “Agent Ace, you are hereby summoned to undertake a high-priority assignment…” He paused, waggling his eyebrows at Sae, who stared back with the enthusiasm of a man awaiting a root canal.

Sae’s jaw tightened, his fingers drumming an impatient rhythm on the desk. He didn’t have time for Shidou’s theatrics—or headquarters’ nonsense. But Shidou, oblivious to the storm brewing across the desk, continued in his mock-epic tone, savoring every word. “With the recent escalation of tensions between Vostaria and Ausillias, teetering on the brink of all-out war, you are tasked with a critical mission to restore peace.”

He flipped the page with a flourish, his grin widening. “Operation Nocturnal: The Path to Peace. For this mission, you are required to form a fake family. A wife and a child are needed to complete the cover—”

“Hold hold hold your boat, lil bro,” Sae cut in, his voice sharp enough to slice through Shidou’s theatrics. He leaned forward, elbows on the desk, his green eyes glinting with a mix of disbelief and barely restrained fury. “There is no universe—not a single one—where I’d have a wife or a kid. What kind of fever dream is headquarters cooking up now?”

The blond pouted, clutching the letter to his chest as if Sae had personally insulted his life’s work. “Welp, that’s what the letter says, Sae-kun! And rude—don’t interrupt my performance!” He waved a finger in mock reprimand, undeterred by the death glare aimed his way. “This is art, you know!”

Sae’s hand twitched, as if contemplating whether to strangle Shidou or the idiot at headquarters who approved this plan. “Tell Ness to send a letter back with ‘fuck you’ written in bold. Red ink. Capital letters. Underlined. Twice.”

Shidou gasped, his hand flying to his heart in exaggerated horror. “Sae! Such language! You wound me!” He leaned closer, smirking like a cat that had just knocked over a vase. “But seriously, you have to do it. Orders are orders, and Ness said this one’s non-negotiable. Something about ‘diplomatic immunity’ and ‘blending in with civilians.’ You know, spy stuff!”

Sae groaned, the sound so deep and pained it seemed to echo from the depths of his soul. It was his fifth groan of the day, and it wasn’t even noon. He slumped back in his chair, rubbing his temples as if he could physically massage away the absurdity of this mission. “Fine,” he muttered, the word tasting like ash. “But tell them I’m changing the plan. I’m not playing house with some random woman and a kid they probably rented from a talent agency.”

Shidous eyes sparkled with mischief. “Whatever you say, boss~!” he chirped, blowing a theatrical flying kiss in Sae’s direction. Sae dodged it with the lightning-fast reflexes he usually reserved for dodging bullets on missions—because, frankly, anything remotely intimate with Shidou might as well be classified as an environmental biohazard.

Unfazed by the rejection, Shidou slumped dramatically into the chair, his limbs sprawling like a sulky teenager. With a final flourish, he tossed the letter onto Sae’s desk, where it landed amid the chaos of papers and coffee mugs. “There ya go,” he said, smirking. “Read it, insult it, burn it for all I care. But don’t say I didn’t warn you—this one’s gonna be a wild ride.”

Sae stared at the letter as if it were a live grenade. He could already imagine the bureaucratic nonsense waiting for him inside: code names, cryptic objectives, and probably a detailed itinerary for how to fake domestic bliss. The thought alone made his stomach churn. “Get out,” he said flatly, pointing at the door.

Shidou hopped to his feet, undeterred, and sauntered toward the exit with an exaggerated sway of his hips. “You’ll thank me later, Sae-kun~!” he called over his shoulder, his voice echoing down the hall as he disappeared.

Sae glared at the letter, his fingers itching to shred it. Operation Nocturnal. A fake family. Peace between two warring nations. It sounded like a bad spy novel written by someone who’d watched too many rom-coms. But as much as he hated to admit it, headquarters didn’t send orders like this without a reason. With a resigned sigh, he reached for the letter, bracing himself for the chaos that was about to upend his life.

He told himself again.

It was for peace. 

It was for protection. For himself and his loved ones…His parents, his friends, his little..brother. Some things had to be done, even if it took his dignity.

—

Fake family..world peace..war

The words churned in Sae’s mind like a relentless storm, each one boring deeper into his skull. He sat on the edge of his bed, the dim glow of a single bedside lamp casting long, jagged shadows across his sparsely furnished apartment. The letter from headquarters lay crumpled on the nightstand, its edges slightly bent from where he’d gripped it too tightly. The weight of its contents pressed against him, heavier than any mission he’d been assigned before.

There was no way he was manipulating some random woman into pretending to be his wife. The very idea was absurd—ludicrous, even. Sae Itoshi, the man who’d dodged bullets, disarmed bombs, and infiltrated enemy strongholds without breaking a sweat, playing house? The thought alone made his skin crawl. He could already picture it: awkward small talk over fake dinners, forced smiles for nosy neighbors, and the inevitable chaos of pretending to be something he wasn’t. Domestic. Happy. Normal. It was a role he was singularly ill-suited for.

And yet… the kid part? That, he could maybe handle. Not that he was some secret softie with a hidden knack for parenting—God, no. But a kid? They were straightforward. You give them clear instructions, maybe toss in some snacks, and they’d probably follow along. Or so he hoped. Sae’s experience with children was limited to dodging their sticky hands in crowded marketplaces during missions. Still, a kid felt less… complicated than a fake wife. Less like a lie he’d have to sell with every glance and gesture. And- the kid he was thinking of…he knew quite well, so that made the job easier.

But was it worth it? The question gnawed at him, sharper than the cold air seeping through the cracked window. This wasn’t just another assignment. This was Operation Nocturnal—a mission to prevent a war that could engulf Vostaria and Ausillias, two nations teetering on the edge of annihilation. Failure meant bloodshed, chaos, and a body count that would haunt him for years. Success, though? Success could mean peace. Stability. A chance to prove he was more than just a weapon wielded by headquarters. It could elevate his career, cement his name as the agent who pulled off the impossible. Or it could destroy him. One wrong move, one slip of the mask, and he’d be exposed—his life, and the lives of his family, dangling by a thread. And he couldn’t let anything happen to him.

Sae ran a hand through his dark hair, exhaling a sharp breath that fogged briefly in the chilly room. The risks were insane, but so was the reward. He’d spent years clawing his way through the agency’s ranks, earning the codename “Ace” through blood, sweat, and a stubborn refusal to fail. This mission could be his legacy—or his undoing.

“Whatever,” he muttered under his breath, the word a half-hearted surrender to the chaos of his thoughts. He couldn’t solve this tonight. Not with his head pounding and the weight of the day dragging at his limbs. With a careful, almost reverent motion, he smoothed out the crumpled letter and folded it neatly, tucking it into the drawer of his nightstand. The wood creaked as he closed it, a small, final sound in the quiet apartment.

Sae fell back onto the bed, the mattress groaning under his weight. The ceiling stared back at him, cracked and peeling in places, a map of neglect that mirrored his own frayed nerves. Tomorrow, he’d face the letter again. Tomorrow, he’d figure out how to bend this ridiculous plan to his will..Tomorrow-..he’d go and see him again.—because if there was one thing Sae Itoshi didn’t do, it was follow someone else’s script. For now, though, he closed his eyes, letting the distant hum of the city lull him toward an uneasy sleep, the words fake family, world peace, war still echoing faintly in the dark.

Chapter Text

Knock knock

The sound echoed faintly in the quiet suburban street, swallowed by the hum of distant traffic and the occasional chirp of a bird. Sae stood on the doorstep of his parents’ house, his fist hovering over the faded wooden door. The paint was peeling at the edges, revealing weathered gray wood beneath—a stark contrast to the pristine home he remembered from his childhood. He shifted his weight, the gravel crunching under his boots, and waited.

Silence.

His patience, already threadbare after a sleepless night wrestling with the absurdity of Operation Nocturnal, was fraying by the second. He glanced at his watch—15 minutes he’d been standing here, ringing the bell and knocking like some persistent salesman. His parents were supposed to be home. They always were. Ever since he was a kid, they’d been borderline hermits, rarely leaving the house unattended. “The world’s too chaotic,” his mother used to say, her voice tinged with a quiet paranoia. “Better to stay where it’s safe.” So where the hell were they now?

Bang bang bang!

Sae’s knuckles slammed against the door with more force than necessary, the sound sharp and jarring in the still morning air. His irritation was spilling over, a hot, restless energy that made his jaw clench and his fingers twitch. He’d driven two hours out of the city to get here, hoping to talk to his parents about the mission- well..more like lying since they could never find out—hoping, maybe, they would allow him to take a certain someone…. But this? This was just another headache he didn’t need.

“This is bullshit,” he muttered under his breath, the words sharp and bitter. He stepped back, scanning the house for signs of life. The curtains were drawn, the windows dark. The mailbox was stuffed with uncollected flyers, a few spilling onto the ground like forgotten confetti. A faint unease prickled at the back of his neck, but he shoved it down. He wasn’t here to play detective—he just needed someone.

Out of sheer frustration, Sae reached for the doorknob, giving it a half-hearted rattle, expecting resistance. If this didn’t get their attention, he’d have to call and deal with his mother’s inevitable lecture about “showing up unannounced.” But when he twisted the knob—

Click.

The door swung open.

Sae froze, his hand still gripping the cold brass. The hinges creaked softly, and a sliver of darkness spilled out from the unlit hallway beyond. His pulse quickened, though he’d never admit it. His parents never left the door unlocked. Not in this neighborhood, not with their near-obsessive caution. He leaned forward, peering into the house. The air inside was stale, carrying a faint musty scent, like a room that hadn’t been aired out in days. The living room was just visible in the dim light—furniture undisturbed, a thin layer of dust coating the coffee table. No signs of struggle, but no signs of life either.

“Mom? Dad?” His voice sounded louder than he’d intended, cutting through the eerie silence. No answer. He stepped inside, his boots thudding softly against the hardwood floor. The unease he’d tried to ignore was growing now, a tight knot in his chest. Something was wrong. He could feel it in the way the house seemed to hold its breath, in the way the silence pressed against him like a physical weight.

Sae’s hand instinctively drifted to the concealed holster at his hip, a reflex honed by years of training. He wasn’t sure what he expected to find—a burglar, a trap, or just his parents’ eccentricities taken to a new extreme—but he wasn’t taking chances. Not today. Not with a mission like Operation Nocturnal looming over him, and certainly not with the memory of that damned letter still burning a hole in his mind.

He took another step, the floorboards creaking under his weight, and called out again. “Anyone home?”

The silence answered back.

.

.

.

“Agh—!” A small figure stumbled from around the corner, a chaotic tumble of colorful plastic toys spilling across the hardwood floor. Sae’s hand instinctively snapped to his secret weapon compartments, his pulse spiking for a fleeting moment before the figure scrambled upright, a wide, toothy grin breaking through the gloom of the unlit hallway. “Oh—hi, Nii-chan!!!” the boy squealed, his voice a burst of sunshine that felt jarringly out of place in the silent house. He waddled toward Sae, arms flung wide, an action figure dangling precariously from one grubby hand.

Rin.

The sight of his little brother—messy black hair, green eyes mirroring his own, and that boundless energy despite everything—sent a pang through Sae’s chest.

Rin, the whole reason he came here.

but not like this. Not alone in a house that felt more like a tomb than a home.

“Hi, Rin,” Sae said, his voice softer than he meant it to be. He crouched down to Rin’s level, the floorboards groaning under his weight, and reached out to gently squish the boy’s cheeks. They were thinner than he remembered, the baby fat starting to hollow out in a way that made Sae’s stomach twist. Rin giggled, swatting at Sae’s hands with his small fingers, but there was a faint smudge of dirt on his face, and his oversized sweater was stained with what looked like days-old strawberry milk stain. “Where’s Mom and Dad?”

“Not home!” Rin chirped, rocking back on his heels with a grin that didn’t quite reach his eyes. “They’ve been gone for a while. Said they’d be back, but I’m in charge till then!” He puffed out his chest, clutching his toy like a badge of honor, but the words hit Sae like a punch to the gut.

“A while?” Sae’s voice sharpened, his eyes narrowing as he scanned Rin more closely. The kid’s hair was tangled, his socks mismatched, and the living room behind him was a mess—toys strewn everywhere, an empty cereal box tipped over on the coffee table, and a blanket crumpled on the couch like a makeshift bed. “How long’s ‘a while,’ Rin?”

Rin shrugged, his attention drifting to the action figure in his hand. “Dunno. A bunch of days? They said it was important, and I had to be a big boy.” He beamed up at Sae, but there was a flicker of something else in his expression—uncertainty, maybe, or loneliness masked by his childish bravado.

Sae’s jaw clenched, a slow burn of anger igniting in his chest. His parents weren’t just gone—they’d left a five-year-old alone for days? The same parents who used to check the locks three times before bed and wouldn’t let Sae cross the street without holding their hands until he was fourteen? The unlocked door, the musty air, the dust settling over the furniture—it all painted a picture that didn’t add up. And Rin, oblivious as he was, shouldn’t be fending for himself like this. The cereal box, the dirty clothes, the toys scattered like a trail of breadcrumbs—they weren’t signs of a kid playing. They were signs of- nevermind.

He straightened, his hand lingering on Rin’s shoulder as he guided him toward the living room, where the faint morning light filtered through drawn curtains. The room felt stale, the air heavy with the scent of unwashed dishes and abandonment. Sae’s mind churned, the words from that damned letter—fake family, world peace, war—colliding with this new, unsettling reality. Had his parents’ absence been planned? I know what your thinking..‘isn’t sae being a bit too dramatic?’ Yes he is- but spies must always be cautious…In reality, they probably just… left Rin behind, like some forgotten piece of luggage.

“When did they leave, Rin?” Sae asked, keeping his tone steady to avoid alarming the kid. He sat on the couch, pulling Rin onto his lap, though the boy squirmed, more interested in his toy than the interrogation. “Tell me exactly what they said.”

Rin scrunched his nose, thinking hard. “They said they had to go do something super important. Mom hugged me, and Dad said to stay inside and not open the door for strangers. They left me snacks!” He pointed proudly at the coffee table, where a half-empty bag of chips sat next to a pile of candy wrappers. Sae’s stomach churned. Snacks. That’s what they’d left their son to survive on?

“And you’ve been here alone since then?” Sae pressed, his voice tight. He brushed a tangle of hair from Rin’s forehead, noticing how the kid’s eyes were a little too bright, like he was fighting to stay cheerful.

“Yup! I’m okay, Nii-chan! I’ve got my toys, and I watched cartoons!” Rin’s grin faltered for a moment, and he looked down at his action figure, fidgeting with its arm. “But… it’s kinda quiet sometimes.”

Sae’s heart clenched, a rare crack in his usual armor. Rin was just a kid—too young to understand how wrong this was, too young to be left to fend for himself in an empty house. The anger in Sae’s chest flared hotter, directed at his parents, at headquarters, at the whole messed-up situation. He’d come here looking for Rin…in a stable condition, taking him with before diving into the chaos of Operation Nocturnal. Instead, he’d found his little brother abandoned, and a house that felt like it was hiding secrets.

“Alright, kid,” Sae said, forcing a calm he didn’t feel. He lifted Rin off his lap and stood, offering his hand. “Let’s clean up this mess, and then we’re gonna figure out what’s going on. You’re not staying here alone anymore.”

Rin’s eyes lit up, and he grabbed Sae’s hand with both of his, tugging him toward the scattered toys. “Deal! But you gotta play heroes with me after, okay? You’re the grumpy hero, and I’m the cool one!”

Sae snorted, the ghost of a smile tugging at his lips despite the storm in his mind. “Grumpy, huh? We’ll see about that.” He ruffled Rin’s hair, but his senses stayed sharp, scanning the room for anything out of place—a note, a clue, anything that might explain where his parents had gone and why they’d left Rin behind. The mission, the unlocked door, and now this—it was all starting to feel like pieces of a puzzle he didn’t want to solve, but couldn’t ignore. For Rin’s sake, and maybe for his own, he’d get to the bottom of it.

”Oh- and- don’t worry nii-chan! I’m used to them leaving so it’s okay- they just have so many business trips, hehe~!”

…

”Right…”

—

Sae’s gut had already told him the truth: their parents weren’t coming back anytime soon. The realization sat like a lead weight in his chest, heavy and unyielding. He stood in the cluttered living room, the faint hum of a flickering fluorescent bulb overhead cutting through the oppressive silence. The house felt like a hollow shell—dust motes drifting in the slanted light, toys scattered like remnants of a life abandoned, and Rin’s makeshift nest of blankets on the couch screaming neglect. His parents’ absence for a ‘quick’ errand or a trip. Days, maybe weeks, had passed, and they’d left a five-year-old to fend for himself. The thought made Sae’s blood boil, his hands clenching into fists at his sides.

He needed them back. Not for some heartfelt family reunion, but for logistics. He couldn’t just scoop Rin up and leave without their approval—not legally, anyway. The agency had strict protocols, and Sae, despite his rebellious streak, knew that taking a minor without parental consent would be a bureaucratic nightmare. Headquarters would have his head, and Ness would probably delight in writing him up for it. But the longer he stood in this eerily quiet house, watching Rin clutch his action figure like a lifeline, the less Sae cared about protocol. He wanted to take Rin far away from this place—somewhere safe, somewhere that didn’t reek of abandonment and unanswered questions. Hell, he could tell Ness to send a threatening message to his parents, or let headquarters deal with the fallout. They’d assigned him Operation Nocturnal, hadn’t they? A fake family to prevent a war? Surely they could handle a real family crisis.

Sae sighed, the sound heavy with frustration and something dangerously close to despair. He ran a hand through his dark hair, his sharp green eyes scanning the room for answers that weren’t there. The letter from headquarters, still tucked in his jacket pocket, burned against his chest. Fake family. World peace. War. And now this—Rin, alone, and parents who’d left him without a care.

He crouched down again, leveling his gaze with Rin, who was now sprawled on the rug, staging an elaborate battle between his action figure and a stuffed dinosaur. “Rin,” Sae said, keeping his voice steady but firm, “do you know where your birth certificate is? Or any other important documents?”

Rin’s head popped up, his green eyes wide and sparkling with pride. “Yup! I put them away myself!” he declared, puffing out his chest as if he’d single-handedly saved the world. He scrambled to his feet, nearly tripping over a stray block, and tugged at Sae’s sleeve. “Come on, Nii-chan, I’ll show you!”

Sae’s lips twitched despite himself. “Of course you did,” he muttered, half-exasperated, half-impressed. Only Rin would take it upon himself to organize legal documents at five years old. The kid was a whirlwind of chaos and competence, and Sae couldn’t decide if that made him want to laugh or worry even more.

—

Chapter Text

Just realised I have to update 2 fics every day 😹 (This one and the new one ‘Forget-me-not’)

—

“-chan, where we going?” His little brothers small voice piped up from the backseat, brimming with curiosity. The five-year-old had his face pressed against the car window, his breath fogging the glass as he stared wide-eyed at the world rushing by. The trees lining the suburban road blurred into a mosaic of green and gold, their leaves catching the late afternoon sun. Rin’s owl-like eyes sparkled with wonder, as if he were seeing the outside for the first time in ages—an observation that twisted Sae’s heart like a knife. How long had the kid been cooped up in that empty house, surviving on snacks and cartoons?

“My place,” Sae replied softly, his voice a low contrast to the hum of the car engine. His eyes stayed fixed on the road, navigating the familiar curves out of the suburbs, but his peripheral vision never strayed far from Rin. He caught glimpses of the boy’s reflection in the rearview mirror—messy black hair, a too-big hoodie slipping looking giant on him, and that bright, trusting grin that made Sae’s chest ache. Rin was okay, for now, but Sae’s knuckles whitened on the steering wheel as he thought of their parents’ absence. Days, maybe weeks, and they’d left a five-year-old to fend for himself. The anger simmered just beneath his calm exterior, ready to boil over.

Rin’s attention snapped away from the window, his big eyes locking onto Sae with a mix of excitement and uncertainty. “Gonna live with Nii-chan forever…?” The question hung in the air, innocent but heavy, like a pebble dropped into still water. Rin’s small hands clutched his action figure tightly, as if it could anchor him against the uncertainty of his world turning upside down.

Sae’s throat tightened, but he kept his tone steady, forcing a small, reassuring smile. “Of course, kid. Why else do you think I packed all your stuff?” He nodded toward the backseat, where a duffel bag stuffed with Rin’s clothes, toys, and that carefully organized folder of documents sat haphazardly next to a pile of blankets. The sight of it—Rin’s entire life crammed into a single bag—made Sae’s jaw clench. It wasn’t right. A kid shouldn’t have to carry his world in a duffel, not when his parents were supposed to be there to hold it together.

Rin’s face lit up, his grin stretching ear to ear as he kicked his legs against the seat. “Yay! Nii-chan’s house! Do you have a big TV? Can we watch hero shows? Oh, oh, do you have snacks?” His questions tumbled out in a rush, each one brighter than the last, as if the idea of living with Sae had erased the loneliness of the past weeks. But Sae caught the faint tremor in his voice, the way his fingers fidgeted with the action figure’s arm. Rin was putting on a brave face, but he was still just a kid, abandoned and grasping for something stable.

“We’ll get a big TV if I don’t have one,” Sae said, his voice lighter than he felt. “And yeah, we’ll watch your hero shows. I’ll even get you those gross gummy snacks you like.” He glanced at Rin in the mirror, catching the boy’s delighted gasp. But beneath the banter, Sae’s mind was racing. Taking Rin wasn’t just a spur-of-the-moment decision—it was a line in the sand. He’d meant what he said about keeping Rin with him, but the logistics were a nightmare. Then there was Operation Nocturnal, looming like a storm cloud. A fake family to prevent a war between Vostaria and Ausillias, and now a real family crisis dropped in his lap. Coincidence? Sae didn’t believe in those. Whatever, at least he got the kid part done with- which was good enough.

He adjusted his grip on the wheel, his thoughts drifting to the folder of documents tucked in Rin’s bag. The birth certificate, the medical records—proof that Rin was his brother, proof that Sae had a claim if their parents didn’t resurface. He’d need those if headquarters or anyone else tried to interfere.

“Nii-chan?” Rin’s voice broke through his thoughts, softer now. He was leaning forward, his small hands gripping the edge of the car seat. “You’re not gonna leave me too, right?”

The question hit Sae like a sucker punch, stealing the air from his lungs. He glanced at Rin in the mirror, seeing the flicker of fear in those big green eyes, and something in him cracked. “Never,” he said, the word fierce and unwavering. “You’re stuck with me, kid. Got it?”

Rin’s smile returned, brighter than the sun filtering through the trees. “Got it!” He settled back, humming a tuneless song as he resumed his vigil at the window, pointing out a bird perched on a branch.

Sae’s gaze returned to the road, but his resolve hardened like steel. He’d take Rin to his apartment, get him settled, and then dig into whatever mess their parents had left behind. If it was tied to Operation Nocturnal, he’d find out. If it was something else, he’d handle it. And if headquarters tried to pull him away from Rin for their fake-family charade, they’d have to pry him away with a crowbar. For now, though, he’d focus on the kid in the backseat, whose world was about to change—again.

—

The thought of living with his Nii-chan again sent a burst of joy through Rin’s small frame, like fireworks exploding in his chest. He bounced in the backseat of Sae’s car, his legs kicking against the seat as he clutched his action figure, its plastic cape flapping with every enthusiastic wiggle. The world outside the window—trees, houses, a stray cat darting across the street—blurred into a colorful backdrop to his excitement. Nii-chan’s house! Big TVs, hero shows, gummy snacks! It was like a dream come true. But in the back of Rin’s mind, a tiny seed of doubt lingered, whispering questions he couldn’t quite shake. Why had Nii-chan shown up out of nowhere? Why was he taking Rin away now? He trusted Sae with all his heart—Nii-chan was his hero, after all—but something felt… weird.

Rin, being the curious and brutally straightforward five-year-old he was, didn’t hesitate to ask. He leaned forward, his big teal eyes fixed on the back of Sae’s head, where dark hair stuck out in messy tufts. “But why though?” he blurted, his voice cutting through the hum of the car engine.

Sae’s grip on the steering wheel tightened slightly, his gaze flicking to the rearview mirror. “Huh?” he said, his tone casual but with a faint edge, like he’d been caught off guard.

“Why do I need to live with you?” Rin pressed, tilting his head. It wasn’t that he didn’t want to—Nii-chan was the coolest person in the whole world, cooler than even the heroes on TV! But it was still strange. Mom and Dad had been gone for ages, leaving Rin with his toys and snacks, and then Nii-chan showed up like a superhero swooping in to save the day. Why now? What had changed?

Sae’s lips quirked into a small, practiced smile, the kind he used when he didn’t want to explain too much. “Oh, I just missed my little brother, that’s all,” he said, his voice soft but steady, like he was trying to wrap the words in a warm blanket. He glanced at Rin in the mirror, his green eyes catching the fading sunlight, and added, “Thought it’d be fun to hang out, you know?”

Rin’s heart did a happy flip, his grin stretching so wide it made his cheeks ache. Nii-chan missed him! That was the best news ever! He hugged his action figure tighter, practically vibrating with excitement. But that tiny seed of doubt still niggled at him, like an itch he couldn’t scratch. Nii-chan’s answer made sense, but there was something… off. Rin wasn’t just any kid, after all. He had a secret—a super secret—that nobody knew about, not even Nii-chan.

Rin could read minds.

It was his special power, something he’d been born with, like a hidden spark in his brain. He’d discovered it by accident when he was three, hearing Mom’s thoughts about dinner while she was chopping carrots. At first, he thought everyone could do it, but when he tried telling his parents, they just laughed and said he had a “big imagination.” So Rin kept it to himself, using it to figure out if people were telling the truth or hiding something. And right now, he needed to know what was going on in Nii-chan’s head.

Rin scrunched his face, focusing as hard as he could. He imagined a little door in his mind swinging open, letting him peek into Sae’s thoughts. It was always tricky—grown-up brains were messy, full of jumbled words and feelings—but Rin was good at it. He squeezed his action figure for luck and dove in.

‘Phew..he believed it. Eh, it’s true though. I really did miss him but I can’t let him know about me being a spy or the mission.’

Gasp!

Rin’s eyes went wide, a gasp slipping out before he could stop it. A spy? Nii-chan was a spy? Like the secret agents in his favorite hero shows, with cool gadgets and sneaky missions? That was the coolest thing he’d ever heard! His heart raced, and he bounced in his seat, barely containing the urge to shout it out loud.

“Huh?” Sae’s voice snapped Rin back to reality. He glanced over his shoulder, one eyebrow raised, his sharp green eyes scanning Rin’s face. “You okay, kid?”

“Y-Yes, Nii-chan!” Rin squeaked, slapping a nervous chuckle over his shock. He hugged his action figure to his chest, trying to look normal, but his mind was spinning. A spy! That explained everything—the sudden visit, the packed bag, the way Nii-chan kept looking around like he was checking for bad guys. Rin wanted to ask a million questions—Did Nii-chan have a laser watch? Did he fight villains? Was he on a mission right now?—but he bit his lip. If Nii-chan was keeping it a secret, maybe Rin’s power was supposed to stay secret too. For now.

Sae’s gaze lingered on Rin for a moment, suspicion flickering in his eyes, but he turned back to the road. “Alright, weirdo,” he said, a hint of amusement in his voice. “Just don’t go gasping like that when we’re eating dinner. You’ll choke on your food.”

Rin giggled, but inside, he was buzzing with excitement. Living with a spy! Maybe he could help Nii-chan with his mission, like a sidekick! But then another thought hit him, dimming his grin. If Nii-chan was a spy, did he only really come back because he needed something..? No! Nii-chan said he missed him-! He would never lie!

Sae caught the shift in Rin’s mood through the rearview mirror, his own thoughts racing. The kid was too perceptive for his own good, and that gasp hadn’t been random. Sae didn’t know about Rin’s mind-reading trick, but he knew his brother well enough to sense when something was up. He’d have to be careful—Rin couldn’t know about Operation Nocturnal, the fake family, or the war looming between Vostaria and Ausillias. Not yet. Not ever, if Sae could help it. For now, he’d keep Rin safe, only use him in the mission when necessary because he would never hurt him..and rewrite headquarters’ script to fit his own terms. Starting with making sure his little brother never felt abandoned again.

“Almost there, kid,” Sae said, his voice softer now. “You’re gonna like my place. It’s not much, but it’s got you and me. That’s enough, right?”

Rin’s grin returned, brighter than ever. “Right, Nii-chan!” he chirped, his doubts pushed aside by the thought of being with his hero. Spy or not, Nii-chan was his favorite person in the world, and that was enough for now.

__

Chapter Text

Woahhhhhh…” the small voice echoed through the spacious living room, his wide green eyes sparkling with awe as he took in his new surroundings. Sae’s “home” was nothing like the cluttered, musty house Rin had been left in for weeks. The high ceilings, sleek hardwood floors, and floor-to-ceiling windows made the place feel like something out of one of Rin’s hero shows—a secret hideout for a superhero, or maybe even a spy. He spun in a slow circle, clutching his action figure, his mouth hanging open as he stared at the modern furniture, the gleaming kitchen island, and the massive flat-screen TV mounted on the wall. “Nii-chan, this is so cool!” he squealed, his sneakers squeaking as he darted toward the window to gawk at the city skyline twinkling in the early evening light.

Sae leaned against the doorway, arms crossed, watching Rin’s excitement with a faint, bittersweet smile. The house was new—bought specifically for Operation Nocturnal. He couldn’t risk bringing Rin to his real apartment, a cramped, nondescript place littered with mission files and takeout containers, where one wrong move could expose his double life as a spy. This place, with its pristine walls and carefully staged decor, was a blank slate—a strategic choice. If the mission went south, if Vostaria and Ausillias tipped into war, or if headquarters’ plan for a fake family blew up in his face, Sae could disappear with Rin and start over. The thought should’ve been reassuring, but it only tightened the knot of unease in his chest.

He’d confirmed with a quick call to Ness while packing Rin’s things: their parents were fine, just off on some extended trip to “find themselves” or whatever nonsense they’d spouted. No connection to the mission, no shadowy conspiracy—just typical, selfish neglect, leaving a five-year-old to fend for himself with a bag of chips and a vague promise to return “soon.” The news had doused Sae’s suspicions but fueled his anger. A trip. They’d left Rin for weeks over a trip. If he wasn’t so focused on keeping Rin safe, he’d have tracked them down himself to give them a piece of his mind.

“Nii-chan, do you live here all the time?” Rin asked, snapping Sae out of his thoughts. The boy had climbed onto the couch, bouncing on the cushions as he pointed at the TV. “Can we watch hero shows now? And—and do you have a secret room? Like for gadgets?” His eyes gleamed with mischief, and Sae’s stomach did a small flip. Rin’s earlier gasp in the car still nagged at him—the kid was too perceptive, and Sae had no idea about the mind-reading trick Rin was hiding. Poor him, he doesn’t even know he now has to be extra careful not to think about Operation Nocturnal too loudly.

“Not all the time,” Sae said, keeping his tone casual as he dropped Rin’s duffel bag by the couch. “Just got this place to spend time with my baby brother. And yeah, we’ll watch your shows, but only if you unpack your stuff first.” He raised an eyebrow, nodding toward the bag. “No secret rooms, though. Sorry to disappoint.”

Rin pouted, flopping dramatically onto the couch. “Aww, no gadgets? But you’re so cool, Nii-chan!” He paused, then grinned slyly, like he was testing something. “You sure there’s no… spy stuff here?”

Sae froze for a split second, his sharp green eyes flicking to Rin. The kid’s tone was playful, but there was a glint in his eyes that made Sae’s spy instincts tingle. He’s five, Sae reminded himself, shaking off the paranoia. “Spy stuff?” he said, snorting. “You’ve been watching too many cartoons, Rin. Come on, let’s get your room set up.”

Rin giggled, clearly delighted by the dodge, and hopped off the couch to grab his bag. As he dragged it toward the hallway, chattering about which hero show was the best, Sae’s mind churned. The house was a cover, just like the fake family he was supposed to build for the mission. Headquarters wanted him to play happy families with a stranger and a kid to infiltrate some diplomatic circle and prevent a war. But now, with Rin here, the closest thing to a family the headquarters were getting.

He followed Rin down the hall to a spare bedroom, already furnished with a kid-sized bed and a shelf for toys. Rin gasped again, dropping his bag to dive onto the bed, rolling around like it was a trampoline. “This is my room?” he asked, his voice muffled by the pillow he’d face-planted into.

“Yup,” Sae said, leaning against the doorframe. “All yours. But don’t break anything, or you’re cleaning it up.” He kept his tone light, but his eyes scanned the room, mentally cataloging exits and sightlines out of habit. This house was a fortress in disguise—security cameras hidden in the light fixtures, reinforced locks, and a burner phone stashed in a drawer. If Operation Nocturnal went wrong, he’d be ready. For now, though, it was just him and Rin, and that was enough to keep him grounded.

As Rin started unpacking his toys, arranging them on the shelf with surprising care, Sae’s thoughts drifted back to their parents. A trip. They’d left Rin alone for a trip. The anger flared again, but he pushed it down. He’d deal with them later. Right now, he had a kid to take care of and a mission to navigate. And maybe, just maybe, having Rin around would make this fake-family charade feel a little less like a lie.

“Nii-chan!” Rin called, holding up his action figure triumphantly. “Gonna be with nii-chan forever-!…”

Sae’s lips twitched into a rare, genuine smile. “Yeah, kid,” he said softly. “Forever.” But in the back of his mind, the weight of the mission—and the secrets he was keeping—loomed like a storm on the horizon.

—

Wash your hands,” the older brother instructed, his voice firm but softened by the faint smile tugging at his lips. He crouched down, gently squishing Rin’s chubby round cheeks between his palms, marveling at how they still felt like soft dough despite the weeks of neglect. Rin’s face was a perfect circle, his big green eyes blinking up at Sae with a mix of indignation and affection. People often called Rin a “thoughtless circle”—a nickname that was equal parts accurate and endearing, capturing his boundless energy and carefree spirit. Even now, with his hair a tangled mess and his sweater stained with mystery smudges, Rin radiated a kind of innocent charm that made Sae’s chest ache.

The kitchen of Sae’s new house—bought as a strategic cover for Operation Nocturnal—was filled with the warm aroma of sizzling vegetables and boiling rice. Sae stood at the stove, stirring a pan of stir-fried chicken and broccoli, determined to cook something healthy for Rin. The kid had been surviving on chips, candy, and whatever else he could scavenge from their parents’ abandoned pantry for weeks. The thought of it—Rin, alone, rationing snacks like some castaway—made Sae’s jaw clench, his grip tightening on the spatula. Their parents were off on some self-indulgent trip, leaving their five-year-old to fend for himself. A trip. The sheer irresponsibility of it fueled Sae’s resolve to make sure Rin never went hungry again.

“Otayyy…” Rin pouted, his lips puffing out as he waddled toward the sink, dragging his action figure along like a loyal sidekick. He climbed onto a step stool Sae had set up, his small hands fumbling with the soap dispenser. “But Nii-chan, why can’t we have gummies for dinner?” he asked, tilting his head with a dramatic sulk that could’ve melted anyone’s heart.

Sae snorted, glancing over his shoulder as he added a dash of soy sauce to the pan. “Because gummies aren’t food, kid. You need real stuff—vegetables, protein, the works. Gotta make you strong like those heroes you’re always yapping about.” He kept his tone light, but his eyes flicked to Rin, checking for any signs of lingering hunger or weakness. The kid was resilient, but Sae wasn’t taking chances. He’d already mentally cataloged the fridge’s contents—stocked with fresh produce, chicken, and milk, all bought that morning—and planned a week’s worth of meals to get Rin back to full health.

Ding

A faint metallic clink echoed through the kitchen, sharp and deliberate, like a pin dropping in a silent room. Sae’s hand froze over the pot of simmering soup, the ladle hovering mid-stir. A coin had landed on the counter, just inches from the stove, its polished surface glinting under the fluorescent light. The symbol etched into it—a stylized crescent moon cradling a single star—was unmistakable. Sae didn’t need to look around the house to know where it came from or what it meant. His pulse quickened, but his expression remained a mask of calm, honed by years of training.

It was a secret message.

Sae’s sharp green eyes flicked toward the living room, where Rin was sprawled on the couch, engrossed in a hero cartoon, his action figure waging an imaginary battle against a pile of cushions. The kid was oblivious, humming along to the show’s theme song, his chubby cheeks still smudged with soy sauce from dinner. Good. Sae needed him distracted. He set the ladle down quietly, his movements precise, and picked up the coin, its weight familiar in his palm. With a quick glance to ensure Rin wasn’t watching, he pried it open, the hidden compartment springing apart with a soft click. A slip of paper fluttered out, landing on the counter. The text scrawled across it was in Morse code—dots and dashes inked in a hurried hand.

Of course, Sae could read it. Deciphering codes was as second nature to him as breathing. His eyes scanned the message, translating it in seconds:________________. The words hit like a cold wave, confirming what he’d been dreading. The mission was in full swing now, no more prep time, no more delays. Headquarters was moving fast, and this coin—a covert drop method used only for urgent updates—meant the stakes had just skyrocketed.

Sae’s jaw tightened as he folded the paper and slipped it into his pocket, the coin following with a practiced flick of his wrist. He leaned against the counter, his mind racing.

Guess Operation Nocturnal was in full swing now.

—-

Chapter Text

“Rin, I need to go to work,” His older brothrr said, crouching down to meet his little brother’s big green eyes. His voice was calm but carried a hint of reluctance, as if he were weighing every word. “Are you okay with being home alone for a bit?” He rested a hand on Rin’s shoulder, his thumb brushing the frayed edge of the boy’s oversized sweater. The kitchen behind them still smelled faintly of the soup they’d eaten, the pot now cooling on the stove, but Sae’s mind was elsewhere—on the coded message in his pocket and the ticking clock of Operation Nocturnal. The rendezvous point was 48 hours away, and he needed to move, but leaving Rin in this new house, even with its hidden security measures, felt like a gamble he wasn’t ready to take.

Rin gave a determined nod, his chubby cheeks puffing out with a seriousness that was almost comical for a five-year-old. “I’m okay, Nii-chan!” he declared, clutching his action figure like a talisman. Thanks to his secret mind-reading ability, Rin already knew what Sae’s “work” really meant—spy stuff! The thought sent a thrill through him, his heart racing with images of Nii-chan sneaking through dark alleys or fighting villains like in his hero shows. He was so proud of his big brother, even if he had to keep his powers a secret to avoid freaking Sae out. But as he nodded, a flicker of confusion crossed his face. There was a stranger at the door, leaning against the frame with a grin that was far too wide and far too amused for Rin’s liking.

“Woah! Baby Lashes~!” the man exclaimed, his voice loud and grating, like a cartoon villain who’d had too much sugar. His spiky blonde hair, streaked with neon pink, seemed to glow under the porch light, and his eyes sparkled with a chaotic energy that made Rin instinctively cringe. The man—Shidou, though Rin didn’t know his name yet—strutted into the house uninvited, his sneakers squeaking on the hardwood floor. “Look at this little guy! Same eyes as you but way cuter-!, Sae-kun! Is he part of the thing or what?”

Rin’s small hands tightened around Sae’s leg, his action figure pressed against his chest as he hid half-behind his brother. The stranger’s loudness was overwhelming, and his teasing tone made Rin’s nose wrinkle in distaste. But more than that, Rin’s mind-reading kicked in without warning, picking up Shidou’s (clean and appropriate) thoughts like static on a radio: ‘Kid’s adorable! Bet he’d make a great cover for the fake family. Wonder if Sae’s gonna flip out when I tell him headquarters not approving of him~!’

Rin’s eyes widened, his grip on Sae tightening. He didn’t really understand what the guy was thinking yet his only thought was- This guy knew about Nii-chan’s spy stuff! Rin’s excitement battled with his unease—Shidou seemed like trouble, but maybe he was one of the good guys, like Nii-chan’s sidekick. Still, Rin stayed glued to Sae, his small frame practically vibrating with curiosity and caution.

Rin peeked out from behind Sae, his mind racing. He focused hard, trying to catch more of Shidou’s thoughts: ‘Sae’s so touchy! Bet he’s freaking out about juggling the kid in the mission. Gotta tell Ness this place is perfect, though—nice cover!’ Rin’s heart skipped. So this house was part of Nii-chan’s spy stuff! He wanted to ask a million questions, but he bit his lip, remembering his secret had to stay hidden. Still, Shidou’s loud voice and weird hair made him nervous, and he clung tighter to Sae’s leg.

“Shut it, Ryuusei.” Sae growled, his voice low and laced with barely restrained irritation. He stood rigid in the kitchen, his green eyes narrowing as Shidou leaned against him, far too close for comfort. The man’s neon-pink-and-blonde hair practically glowed under the overhead light, and his grin was all teeth, like a shark sizing up its next meal. Sae’s hand twitched, itching to shove Shidou away, but he kept his composure, hyper-aware of Rin’s small form right there, watching the scene unfold with a mix of curiosity and unease.

Shidou, oblivious to—or more likely, reveling in—Sae’s annoyance, draped an arm over Sae’s shoulder, his voice dripping with mock affection. “Oh, Sae-kun, don’t be such a grump~! I’m just here to help with the mission, you know? Gotta make sure our star agent’s ready to play house!” His eyes flicked to Rin, who was clutching his blanket and action figure, standing just a few steps away. Shidou’s grin widened, and he cooed, “Aww, look at Baby Lashes pouting! So cute! You jealous I’m stealing your Nii-chan’s attention, huh?”

Rin’s chubby cheeks puffed out in a dramatic pout, his green eyes narrowing at Shidou. He didn’t like this guy—not one bit. The loud voice, the weird hair, the way he was practically hanging off Nii-chan—it was all wrong. Rin hugged his blanket tighter, his small frame bristling with protective instinct. Nii-chan was his big brother, not this obnoxious stranger’s! The cooing only made it worse, and Rin’s nose wrinkled as if he’d smelled something bad.

Unbeknownst to Sae or Shidou, Rin’s secret mind-reading ability kicked in, his curiosity overriding his annoyance. He scrunched his face, focusing hard on Shidou’s chaotic brain, the little door in his mind swinging open. ‘Heh, kid’s got Sae’s glare down pat! Bet he’d be a riot on the mission. Wonder if we can convince the higher ups some more— make things real spicy~!’ Rin’s eyes widened, a mix of indignation and excitement bubbling up… that sounded kind of cool. Still, Rin didn’t trust Shidou’s vibe, and he edged closer to Sae, his blanket trailing on the floor like a cape.

“Ryuusei,” Sae said, his voice a dangerous whisper as he shrugged off Shidou’s arm with a sharp movement. “Back. Off. And stop messing with my brother.” He stepped slightly in front of Rin, a protective wall, his expression cold enough to freeze the room. Sae’s mind was racing—Operation Nocturnal was already a logistical nightmare, with the fake wife and kid cover story, a rendezvous in 48 hours, and a war to prevent. Now Shidou was assigned as his helper, stirring up chaos and risking Rin’s safety by even being in the same room.

Shidou raised his hands in mock surrender, his grin unfazed. “Alright, alright, Sae-kun! No need to get all prickly! I’m just sayin’, this kid’s got potential. Look at that pout—could charm a diplomat!” He winked at Rin, who stuck out his tongue in response, earning a theatrical gasp from Shidou. “Ouch, Baby Lashes, you wound me!”

Rin clung to Sae’s leg, his pout deepening, but his mind was buzzing. He focused again, this time on Sae’s thoughts, catching fragments of his brother’s tightly guarded brain: ‘Gotta get Shidou out before he says too much. Rin can’t know about the mission. Need to secure the house and prep for the rendezvous without him noticing.’ Rin’s heart skipped. Nii-chan was trying so hard to protect him, but Rin wasn’t a baby! He could help—maybe. His powers were a secret, but they’d already told him so much about Nii-chan’s spy life. Maybe he could use them to keep Shidou from causing trouble.

“Rin,” Sae said, his voice softening as he crouched down to meet Rin’s gaze. He ruffled the boy’s messy hair, ignoring Shidou’s lingering presence. “Why don’t you take your blanket and go pick a hero show for us to watch later? I need to talk to this guy for a minute.”

Rin hesitated, his eyes flicking between Sae and Shidou. He didn’t want to leave Nii-chan alone with this weirdo, but he trusted Sae. “Okay, Nii-chan,” he mumbled, dragging his blanket toward the living room. But as he went, he shot Shidou a glare that was almost a perfect miniature of Sae’s, making Shidou chuckle.

“Kid’s gonna be a menace,” Shidou said, leaning against the counter now, his voice lower but still dripping with amusement. “So, Sae-kun, about that fake wife—headquarters picked a real firecracker. You ready to meet her at the rendezvous, or you gonna keep playing big brother instead?”

Sae’s glare could’ve melted steel. “Tell them to go shove a marker up their urethra. I already said I don’t want any fake wife.,” he said, his voice low and final. “And if you call him ‘Baby Lashes’ again, I’ll feed your goldfish to Ness’s dog and make you watch.”

Shidou laughed, undeterred, but Sae’s focus was split—keeping Rin safe, deciphering headquarters’ next move, and surviving Shidou’s chaos. The coin drop’s message burned in his pocket: 48 hours until the rendezvous. With Rin in the house and Shidou stirring the pot, Operation Nocturnal was already off to a messy start.

Rin only listened in around the corner. Wait- fake wife?! Wasn’t the annoying stranger already sticking to his older brother enough..they really didn’t need anyone else. Good thing nii-chan refused!

He peeked around the corner, his blanket slipping slightly as he caught sight of Shidou leaning against the kitchen counter, twirling that weird coin with the crescent-and-star symbol. Sae stood rigid, his arms crossed, his green eyes glinting with irritation that Rin knew all too well. “Ryuusei,” Sae said, his voice low and sharp, “if you’re done wasting my time, spit out the rest of the details. And keep it quiet—Rin’s not supposed to hear this.”

—