shidou ryusei x afab!reader
warnings. scientist!reader, school friends-to-lovers, mutual obliviousness, eccentric partners in crime, controlled laboratory chaos, swearing, very affectionate shidou, public declarations, pure fluff ♡
ryusei follows the sound of an explosion into your laboratory and discovers a girl just as thrilled by dangerous possibilities as he is. somewhere between volatile experiments, impossible goals, and months spent encouraging each other’s worst ideas, neither of you notices that the greatest chain reaction has been building between you two all along.
The first time Shidou Ryusei enters your laboratory, he follows the sound of something exploding.
Technically, it is not an explosion. You will spend a considerable portion of your friendship correcting him on that point, although the distinction becomes difficult to defend when a sharp crack rings through the science building and sends a flock of birds scattering from the roof.
Most students would hear the noise and hurry in the opposite direction.
Ryusei appears in the doorway less than ten seconds later, one hand braced against the frame and a look of delighted curiosity spreading across his face.
You stand safely behind a clear protective screen with your goggles secured over your eyes, watching vivid violet foam climb from a glass container and spill into the broad tray beneath it. Mist curls toward the ventilation hood, the whiteboard behind you is crowded with hurried calculations, and a triumphant laugh escapes you as the reaction swells far beyond the line you marked earlier.
Ryusei’s gaze moves from the overflowing container to your face.
His grin slowly stretches wider.
“That was fucking beautiful.”
You push your goggles onto your head and turn toward him, still clutching your clipboard against your chest. His football uniform is streaked with grass, sweat darkens the roots of his blond-and-pink hair, and his pale eyes shine with the unmistakable excitement of someone who has just discovered a new form of entertainment.
“You aren’t supposed to be in here.”
“That isn’t how experiments work.”
“Then make the next one bigger.”
The suggestion should irritate you. You have spent weeks planning the reaction, and this strange boy has reduced all your work to make it bigger without even asking what you were trying to prove.
Instead, the corner of your mouth begins to rise.
Ryusei notices immediately.
He crosses the threshold without waiting for permission, weaving between the laboratory tables as though he has never encountered a room he could not make himself comfortable inside. His attention jumps from the bubbling foam to the rows of glass containers until he stops beside the enclosed chamber prepared for your next trial.
“What does this do?” You follow his gaze toward the switch beneath his hovering fingers.
“It changes what happens inside the chamber.”
“What happens if I press it?”
“At the setting I was considering?” You glance at the equipment, already imagining the result. “Something our instructor specifically told me not to attempt without supervision.”
His fingers remain poised above the switch.
“You saying I shouldn’t?”
You study him for a moment.
Anyone else might have looked nervous or suspicious. Ryusei looks almost painfully hopeful, as though you have placed the most interesting choice in the world directly in front of him.
Slowly, you set your clipboard aside.
You check that the chamber is sealed, pull the protective screen into place, and lower your goggles again. When you look at him through the clear barrier, your grin matches his completely.
“Do you want to find out?”
Ryusei becomes perfectly still.
It lasts less than a second before laughter bursts out of him, bright and delighted enough to fill the laboratory more completely than the earlier crack.
You retrieve a spare pair of goggles and hold them toward him.
“Your new favorite person.”
He takes them without hesitation.
Ryusei becomes your unofficial laboratory assistant over the following weeks, despite possessing no qualifications beyond excellent reflexes, unreasonable enthusiasm, and a deeply concerning willingness to touch anything labelled experimental.
He begins appearing after football practice so frequently that you stop looking up when the door swings open. His arrival is usually announced by the sound of his bag hitting the floor, followed by an enthusiastic demand to know whether you have prepared anything catastrophic for him.
Your teachers object to his presence at first. Ryusei responds by memorizing the laboratory rules, passing every safety quiz placed in front of him, and becoming surprisingly competent with the equipment.
He never develops caution in the traditional sense.
He simply learns that ruining one of your experiments is far more dangerous than anything stored inside the laboratory.
You toss a clamp in his direction without looking away from the notes in front of you. Ryusei catches it one-handed and positions himself beside the table.
“What happens if I drop it?”
“You destroy three weeks of work.”
“What happens if I hold it higher?”
“And if I turn it sideways?”
You slowly lift your head. “Would you like to discover how quickly I can throw you through that window?”
His grin sharpens. “Is that part of the experiment?”
“Hot.” You roll your eyes and return to your notes, although not before he catches the smile threatening the corner of your mouth. A moment later, his face appears beside yours, close enough that a loose strand of his hair brushes your temple. “You like me.”
“I like having someone expendable nearby.”
He presses a quick kiss to your temple before returning to his position, apparently unaware—or entirely unconcerned—with the way your pen pauses against the paper.
Ryusei touches you as naturally as he reaches for a football. He throws an arm across your shoulders whenever you explain something that interests him, rests his chin on your head while pretending to read your observations, and wraps himself around your waist from behind whenever you spend too long focused on your work instead of him.
When an experiment succeeds, he kisses your cheek and loudly announces that you are a genius. When one fails, he does exactly the same thing, insisting that scientific disappointment requires “emergency morale procedures.”
You return his affection with equal force.
Whenever he arrives boasting about a goal, you drag stools across the laboratory and demand a complete reenactment. He uses discarded boxes to represent defenders while you draw the path of the ball across the whiteboard, and when your diagram fails to account for what he calls his “explosive genius,” he climbs onto the nearest table to argue his case.
“You turned too late,” you tell him, circling the point where his imaginary run should have failed.
“Because the goalkeeper made a terrible decision.”
“Because I’m incredible.”
“Those possibilities can coexist.”
Ryusei places a hand over his heart. “You think I’m incredible?”
“I think the goalkeeper was terrible.”
“Still heard incredible.”
You throw the marker at him.
He catches it between both hands, laughing so loudly that it echoes through the empty room.
Your own victories are never celebrated quietly either. Whenever an experiment produces something brighter or stranger than expected, you forget every expectation that a promising young scientist should behave with dignity. More than once, you have launched yourself into Ryusei’s arms while shouting about the result.
He catches you every time.
Sometimes he spins you between the tables while you laugh against his shoulder. Other times, he lifts you onto the nearest clear surface and stands between your knees while you explain everything at twice your usual speed, his hands settled around your waist and his attention fixed entirely on you.
He does not always understand the details.
He understands the look on your face.
The first time an instructor discovers the two of you celebrating beside a tray overflowing with bright blue foam, she stops in the doorway and closes her eyes.
You immediately point at Ryusei. “His fault.”
He points at you with equal confidence. “Her idea.”
“You asked if I wanted to make it bigger.”
Your instructor opens her eyes and looks between the two of you—both wearing protective goggles, both splattered with harmless blue residue, and both far too pleased with yourselves.
“I regret allowing this partnership.”
Ryusei’s arm tightens around your waist. “Hear that, scientist? We’re official.”
He slaps his palm against yours hard enough to sting.
By the time you notice that your instructor has left, the two of you are already arguing over who deserves credit for the mess.
Other people find you exhausting.
You consider this evidence that they lack imagination.
For years, teachers and classmates have insisted that someone as intelligent as you should behave with greater restraint. They expect a talented scientist to be quiet, detached, and permanently serious, as though enthusiasm might somehow diminish your competence.
Your habit of giving experiments dramatic names, narrating countdowns like rocket launches, and laughing whenever an idea becomes real in front of you is treated as something you will eventually outgrow.
Ryusei never asks you to lower your voice.
The first time you describe an ambitious project everyone else dismissed as impractical, he does not suggest choosing something simpler. He listens with his chin balanced against your shoulder and asks what you need to make it bigger.
In return, when he tells you about an impossible goal he wants to score—the angle too narrow, the movement too strange, his body twisting in a way that would make any sensible player hesitate—you never tell him to become realistic.
You ask when he plans to try it.
Some people are supposed to balance each other.
You and Ryusei prefer amplification.
“You’re completely insane,” he tells you affectionately one afternoon.
You are crouched beneath a worktable, searching for a cable, while he lies on the floor beside you for no practical reason. His goggles sit crookedly over his forehead, and his long legs block the aisle behind him.
“You followed an unidentified noise into a laboratory and trusted a stranger who handed you protective eyewear,” you reply. “I don’t think you’re qualified to diagnose anyone.”
“Best decision I ever made.”
“You also tried to taste the indicator solution.”
You slide out from beneath the table and discover his face hovering directly over yours.
“You’re lucky you’re pretty.”
His eyebrows lift. “Pretty?”
“Would you prefer handsome?”
You place your palm against his face and shove him aside. Ryusei catches your wrist before you can retreat, pressing a kiss into the center of your hand with an enormous grin.
“Love you too, scientist.”
“You say that whenever I insult you.”
“You make insults sound romantic.”
“You once told an open flame you loved it.”
“You proposed to the centrifuge.”
You pull your hand away, although not before he threads his fingers through yours and gives them an affectionate squeeze.
Ryusei says he loves you constantly.
He says it whenever you allow him to start the final stage of an experiment, when you bring an extra drink because you knew he would appear after training, and when you threaten him for stealing your goggles. He writes it between the calculations in your notebook and shouts it from the far end of the hallway whenever he sees you leaving class.
Once, after you corrected one of his teachers so thoroughly that the man abandoned the argument, Ryusei announced in front of everyone that he intended to marry you.
Because he throws every emotion into the world at full volume, you can never tell where the performance ends.
You convince yourself that affection is merely another outlet for his endless excitement.
It is easier than admitting how desperately you want him to mean every word.
The phrase chain reaction becomes yours halfway through the school year.
You are preparing a demonstration for an upcoming science competition when Ryusei arrives with a split lip, grass stains across one knee, and the triumphant expression of someone who has just made several opponents regret challenging him.
He sits on the edge of your worktable while you arrange the materials, swinging one leg and stealing sweets from the bag beside him.
“One reaction starts another,” you explain. “Then that one sets off the next, and it keeps going until something finally stops it.”
He chews thoughtfully. “So one thing explodes—”
“—and makes everything else explode too.”
“That is a terrible explanation.”
You glance at him. Ryusei reaches forward, catching you by the loops of your lab coat and drawing you between his knees. His hands settle comfortably around your waist while he looks up at you, pale eyes shining with the certainty of someone who has just reached a magnificent conclusion.
You stare at him. “We are not a chemical reaction.”
“You get excited, then I get excited because you’re excited, and then you get even crazier because I’m encouraging you.”
“You say that as though you aren’t the one climbing onto tables.”
His grin stretches wider. “Is my explanation wrong?”
“You skipped almost everything important.”
“An increasingly unstable situation that becomes impossible to control?”
“Exactly.” His thumbs sweep slowly over your sides. “Romantic, right?”
He laughs and draws you closer until your knees bump the edge of the table.
You should correct him again.
Instead, your hands settle over his shoulders while warmth gathers beneath your ribs.
“An extremely volatile one.”
After that, the words become a challenge passed between you.
Before an experiment, Ryusei looks at you over the top of his goggles.
Before an important match, you ask him the same questions.
He always gives you the answer you want.
When Blue Lock takes him away, the laboratory becomes unbearably quiet.
There are no arms suddenly appearing around your waist while you work, no demands to see the day’s most dramatic experiment, and no tall striker stretched across the floor where you are trying to walk. Your instructors seem relieved by the peace.
You hate every minute of it.
Before leaving, Ryusei comes to the laboratory in his street clothes and finds you pretending to reorganize equipment that had already been perfectly arranged for over an hour.
His invitation is folded inside his jacket.
His grin is familiar, but the excitement beneath it feels sharper than usual, edged with something restless. Blue Lock promises a sealed building full of strikers willing to tear each other apart for the chance to become extraordinary.
It is exactly the kind of experiment Ryusei would willingly enter.
You would never ask him to remain contained.
Instead, you retrieve a roll of athletic tape from the table.
He offers it without question.
You wrap the tape securely around him before taking a marker and writing two words across the white surface.
Ryusei studies them. “What’s it do?”
His eyes rise toward yours. “And you?”
“I’ll be observing the results.”
“If they ever let you onto television.”
“I’ve got something worth exploding for.”
The words settle between you before you can ask what he means.
Then his hands close around your face, and he kisses your forehead hard enough to push you back half a step.
Another kiss lands on your left cheek.
He presses one to the tip of your nose.
“You’re going to miss me.”
“The laboratory’s accident rate might improve.”
You catch him by the front of his jacket before he can retreat and pull him down, planting an equally loud kiss against his cheek.
The reaction is rare enough to qualify as a scientific breakthrough.
“You’re going to miss me too,” you tell him.
His entire expression ignites.
When he hugs you, nothing about it is restrained. His arms lock around your waist and lift you from the floor while his face disappears against your neck. You cling to him just as tightly, laughing when he begins turning the two of you in a slow circle between the worktables.
“Come back with catastrophic results,” you whisper.
He lowers you far enough to meet your gaze, his grin all teeth and promise.
“Baby, I’m gonna blow the whole experiment apart.”
The Japan U-20 match is the first time you see him again.
You enter the stadium with no intention of behaving like a dignified observer. Several students from your science program are seated elsewhere, having learned from experience that sharing a confined public space with you during one of Ryusei’s matches is inadvisable.
The moment he steps onto the field, you are standing.
From the distance, he looks both exactly as you remember and somehow more alive than he ever did within the boundaries of your school. His body appears incapable of true stillness, every movement carrying the anticipation of something dangerous and magnificent waiting for the right moment to break free.
You shout his name despite the thousands of voices surrounding yours.
There is no reasonable possibility that he can hear you.
Still, his head turns briefly toward the stands.
For one impossible second, you think he is searching for you.
Then the match claims his attention.
Watching Ryusei play has always reminded you of waiting for something to blow.
The warning signs are all there: the growing impatience in his movements, the wild brightness in his eyes, the way every missed opportunity seems to wind him tighter. He does not become discouraged when the path to the goal closes. He becomes excited, as though the resistance only promises a more satisfying release once he finally tears through it.
Something inside him is waiting to ignite.
Itoshi Sae gives him the spark.
The pass rises into the penalty area at an angle that appears impossible only until Ryusei moves. There is no hesitation in him. He throws himself into the air, his body twisting backward as though gravity has personally offended him and he intends to punish it.
The noise of the stadium disappears inside your head.
For one suspended moment, he hangs above the field—wild, weightless, and grinning as though the entire stadium has become his laboratory and he is about to discover exactly how much noise one body can create.
Your hands close around the railing.
“Come on,” you breathe, a grin already spreading over your face. “Show me.”
Ryusei’s foot connects with the ball.
Sound crashes across the stadium as the net snaps behind the goalkeeper. The crowd surges to its feet, but you are already standing, screaming so loudly that pain immediately scratches at your throat.
You throw both arms into the air, laughter breaking through the shout as the enormous screen replays his body suspended above the field.
People around you turn to stare.
On the pitch, Ryusei celebrates with the same wild joy that has filled your laboratory a hundred times. His laughter is visible even from the stands, his entire body overflowing with the release of everything that had been building inside him.
Then he begins searching.
His head turns from one section of the audience to another until his gaze reaches yours.
You know the exact second he finds you.
The fierce exhilaration remains, but recognition moves through it, transforming his grin into something warmer and far more personal.
You raise one hand and tap two fingers against your wrist, directly over the place where you had written on his tape.
Ryusei glances at his own wrist.
Then he points straight toward you.
The stadium is too loud for you to hear him, but you read the words from his mouth easily.
Beside him, Sae follows the direction of his hand.
“The scientist?” he asks.
Ryusei looks offended by the inadequate description.
Sae turns toward the stands in time to watch you mimic an explosion with both hands and nearly strike the spectator beside you.
“You’re both public safety concerns.”
Ryusei’s grin becomes almost predatory.
Sae walks away without answering.
Ryusei shouts after him that silence means agreement.
Whether you find Ryusei after the match or he finds you remains impossible to determine.
The instant you see each other at opposite ends of the corridor, you both begin running.
His legs are longer, so he reaches you first, but you leap before he can slow down. Your arms lock around his shoulders as he catches you beneath the thighs, the collision forcing him backward while laughter bursts from both of you.
“You saw it!” he shouts against your neck.
“Your elevation was disgusting!”
“You threw yourself backward in midair like gravity had personally insulted you!”
You grab his face between both hands and pull back enough to examine him. His skin is still flushed from exertion, sweat darkens the roots of his hair, and the exhilaration glowing inside his eyes has not dimmed.
“Well?” he demands. “How bad was it?”
You narrow your eyes, pretending to inspect him while he practically vibrates beneath you.
“You blew their entire defense apart.”
“You made an entire stadium lose its mind.”
You laugh, unable to contain it any longer.
A triumphant yell tears out of him before he spins you in the middle of the corridor.
You cling to his shoulders, laughing while his voice echoes against the walls. Anyone approaching takes one look at the two of you and wisely changes direction.
When he finally lowers you, his hands remain securely around your waist.
“This wasn’t a competition.”
“Everything’s a competition.”
His expression brightens. “What’s my prize?”
“You scored in front of an entire stadium.”
You tilt your head. “Then what do you want?”
Ryusei looks at you as though the answer should have been obvious from the beginning.
Your heartbeat gives one hard, inconvenient thud.
He says things like that. He has always said things like that.
Before you can decide how much meaning to give the word, footsteps sound behind him. Sae passes the entrance of the corridor and glances briefly in your direction.
“There’s the love of your life,” he says.
Ryusei beams. “Told you she was real.”
You stare after him before slowly turning back toward Ryusei.
“Pretty sure I’ve told everyone.”
“You have never actually asked me out.”
The silence that follows is so complete you could record it as an anomalous event.
“You have never asked me to be your girlfriend.”
“The laboratory had one functioning chair.”
“You slept on me during the train ride to the science competition.”
“You occupied the entire seat.”
“You threatened to strap me to an examination table.”
He stares at you with increasing disbelief.
“I thought we were dating.”
Your laughter erupts before you can contain it.
Ryusei’s arms tighten around you.
“Don’t laugh! I’ve told you I love you, like, a thousand times.”
“You told a Bunsen burner you loved it.”
“It had a beautiful flame. I didn’t want it to meet my parents.”
“You proposed to the centrifuge.”
“That was physical attraction.”
“What the hell was I supposed to think?” he demands, although his own mouth is beginning to curve. “You kiss me, jump on me whenever something blows up, and call me your partner.”
“That’s more serious than dating!”
Your laughter grows until you have to brace both hands against his shoulders.
“You honestly thought I knew?”
“That does not make me telepathic.”
You eventually straighten, though your smile remains and your hands stay resting against him.
The disbelief disappears from his expression, replaced by something bright and intent. He has never been shy and does not become shy now. Instead, he looks at you with the same hungry focus he gives the goal whenever an impossible opening appears.
His hands slide more firmly around your waist.
“That sounded like an order.”
“Be my partner in romantic crime.”
“My favorite catastrophe?”
Ryusei leans closer until the tip of his nose brushes yours. His grin softens without disappearing, warmth settling beneath all his eccentric delight.
“Be the girl who blows shit up with me, screams at my goals, and makes every terrible idea I have even better.”
His forehead comes to rest against yours.
“I don’t want somebody who tries to put me out,” he continues, his thumbs moving restlessly along your waist. “I want you standing there with that crazy grin, asking whether we can make the explosion bigger. I want your experiments, your stupid goggles, and your face in the crowd every time I score something incredible.”
“My goggles are not stupid.”
“They’re hot.” You laugh. “And I want to be the first person you run to whenever you make something impossible happen.” His gaze holds yours, direct and entirely unashamed. “So be my girlfriend, scientist. Officially this time.”
You catch him by the collar and kiss him.
The surprised sound that leaves Ryusei disappears against your mouth as his arms drag you closer, meeting your energy with his own. The kiss is warm, eager, and slightly crooked because neither of you can stop smiling long enough to accomplish it properly.
When he starts laughing, you do too, the sound caught between your lips while one of his hands rises to cradle the back of your head.
He immediately follows, stealing another quick kiss before you can speak.
“That requires further experimentation.”
You kiss him again before he can become any louder.
The laboratory feels right once he returns.
It is too loud, mildly hazardous, and alive in a way it never manages to be without him.
Ryusei enters wearing goggles stolen from your drawer and finds you adjusting a new experiment inside a reinforced glass chamber. He slips behind you, his arms circling your waist while his chin settles against your shoulder.
You glance toward the chamber. “It should glow.”
“Possibly very brightly.”
His smile appears beside your cheek. “Bad idea?”
You check the seal one final time before lowering your goggles.
Turning within his arms, you place one gloved hand over his chest.
He kisses you, bright and quick, before following you behind the protective screen.
You begin the countdown together.
At first, there is only a spark beneath the glass. Then color rushes through the chamber, growing brighter and brighter until the reaction blooms in a flash vivid enough to paint the entire laboratory in light.
Ryusei shouts as though he has just scored another goal.
You laugh just as loudly.
A second later, his arms are around your waist and your hands are catching his face, excitement passing between you as effortlessly as it always has.
One spark becoming another.
A perfect chain reaction.
I HAD TO DO ONE FOR MY MAAAAAN. gods i love him so much.
I have soooo many ideas that i have been writing nonstop these past few day hehe.
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