Work Text:
Senku Ishigami has been surrounded by love all his life:
First with Byakuya, who had adopted him right after his biological parents had passed, guiding him and supporting him during every step of his life, and Taiju who he considers basically a brother now and with whom he has spent basically every single day with ever since he was eight years old.
Then Yuzuriha and her quiet companionship, her gentle friendship, younger than the one with Taiju but not less strong, and the consequential softness his two friends developed for one another in the past few years finally culminating in them getting together, and then Lillian, his father’s lost half of his soul, filling their house with gentle laughs, endeared support and an absurd amount of terrible flirts, really, if Byakuya won’t drop them Senku will choose violence–
So yeah, Senku Ishigami knows what love looks like, knows what it feels like, even if platonic, even if passive.
And now… well.
Now he has the mentalist, and he is so excited for what the future will bring.
Senku has never been in a relationship before, yet he is not scared: he knows first hand that one is able to achieve everything in life with dedication, curiosity and willingness to put oneself out there and share their time with someone they like.
Someone they have grown a bit fond of.
So yeah, his newly achieved relationship with the mentalist is gonna be one billion percent alright since they are both mature people ready to try and learn together about each other, to be there for one another and–
“So, what are you guys doing for Gen’s birthday today?”
Yuzuriha’s voice is light from where she is kneeling in front of the mannequin in her room fixing her latest creation, and every nerve ending in Senku’s body freezes on the spot from where he is standing next to her, helping her with the fabrics during one of their usual dual hang outs.
When her words register, his brain halts, and he blinks, turning slowly towards the girl, “...what?”
Yuzuriha, with her eyes still focused on the mannequin in front of her, just grabs a pin from her wrist pin-holder as she continues serenely, “For Gen’s birthday celebration, you know? He turns twenty-two today!" She chirps excitedly, sticking the pin in the fabric as she spins towards her friend, “I’m curious to know what you guys have… planned…?” Her voice dims as she finally realizes her careless mistake:
Senku is not sure what his face looks like now but he knows, one billion percent for sure, that if the horror on it mirrors the one he sees in his friend's expression then it is no wonder Yuzuriha’s hands fly to her mouth.
“Today,” he gulps, “today is the mentalist's birthday?”
Yuzuriha stands up, hastily waving her hands around as she stumbles on her words, “I– Well–” a breath, “I think I read it a while ago in a magazine or something but– but maybe I remember wrong!” She smiles, awkward and wobbly, “I’m sure Gen would have mentioned it if it was after all, wouldn’t he?”
Senku knows she is trying to reassure him, to dam the tsunami she has inadvertently spilled upon him, but her words only make him frown deeper because–
No he wouldn’t.
Gen, for how self-depictedly superficial or frivolous he calls himself, is actually one of the most selfless people Senku knows and it doesn’t take a genius to realize what’s going on: be it because the boy doesn’t usually celebrate, be it for force of habit or because the mentalist didn’t want to… burden them or something, Senku is sure:
Gen has omitted the information on purpose.
Dropping the fabrics in his hands, he hastily grabs his phone before turning it on and typing something; when Asagiri Gen's Wikipedia page opens, he scrolls down, checking under the info slots—
And there it is, clear as day:
Asagiri Gen—> birthday: 1st of April.
Suddenly, Senku is hit by a memory:
It had been a few months ago, well before the two of them had gotten together, when he and the mentalist had just finished discussing their latest debate topic and the older boy had insisted so much he was right that Senku had had to go looking for an old Encyclopedia to finally prove him wrong only for the book to confirm the trashy mentalist's point, causing Senku to slam his head against the table as he murmured something about pigheaded mentalists and their stubborn convictions— that had the older boy hum cockily, "Of course I was not gonna concede defeat, what did you expect, Senku-chan?” He smiled mischievously at him, “I’m an Aries, after all, ire-fay runs through my soul~”
Senku’s so stupid:
An Aries, the other had said, had carelessly mentioned months ago, so it was logical to conclude that his birthday falls between March 21st and April 20th.
The young scientist often proclaims that a man doesn't talk about his birthday for no reason, doesn't parade the information to others randomly, and yet… he should have known.
He should have known, hell, or should have at least asked when spring had approached, because now he is completely unprepared with no idea of what to give the other and a bitter taste of disappointment on his tongue.
It's true that they have been together for only a couple of weeks, but…
Raising his eyes to meet Yuzuriha's worried ones, he finally opens his mouth, “I did not know,” he frowns, clenching his fists, “he did not tell me today was his birthday and I– I should have asked him when it fell.”
Heck, to find out by a google search…
A man doesn’t talk about his birthday for no reason, sure… but a partner should ask; a good partner, at least, and the boy mentally curses himself for his lack of preparation.
But Ishigami Senku is still a man of practicality, a man of science and pragmatism through and through, so he allows himself only half a second of self-scolding before he lifts his gaze back up, staring straight into his friend’s eyes, “I’m sorry Yuzuriha but I have to go.” He states, apologetic, but the girl just smiles brightly at him, ever so kind, ever so supportive, “Go Senku, don’t you worry about me!”
“Thank you, Yuzuriha.”
He basically runs outside her house, hastily looking at his wrist watch and cursing when he realizes it’s already well past eleven o’clock and that he doesn't have much time, nor any clue of what to do: he could run to the mall to look for something but he fears that, since he doesn't have any specific idea, a wider amount of options could actually make the choice harder.
Fuck, what a shitty situation—
He racks his brain, trying to come up with a better solution, something more personal and special for Gen– when a sudden memory hits him, making him pause in the middle of the road, considering: it would take him all day and an absurd amount of trial and error, but–
It would be perfect.
If he manages to, if he is able to do what he set his mind on… well, he just hopes the mentalist will like it.
Looking down at his watch he mentally notes everything he will need, carefully creating a mental list and road map to obtain his objective, and he grins excitedly when he realizes that he’s only missing a few things; he doesn't have much time though and the chance for errors is greatly high, yet he knows that that might be just the greatest thing he could come up with today, so he has to try.
No, he has to succeed.
There is no time to waste so he starts walking again as the idea in his head crystallizes, making him take big, purposeful steps.
First stop: a combini.
“Oh my, my! How ice-nay of you to invite me over, Senku-chan dear~”
Gen sing-sangs as he steps inside the Ishigami-Weinberg household, sitting down on the genkan to remove his shoes and setting them neatly next to the younger’s ones, and Senku grins, absentmindedly saying something in answer as his fists clench in trepidation: the other boy has arrived just as he was done, and Senku is glad everything had align perfectly so that he’d managed to finish what he had set his mind to before dinner time.
Now, he just hopes Gen will like what he did.
He had invited the other over with a simple excuse, asking the older boy to help him with some basic experiments as a way to spend some time together having dinner, chatting and enjoying some alone time after a few days without seeing each other due to both of their busy schedules; Senku is actually extremely glad that the older boy had been able to come since, due to a series of fortunate events, Gen’s pre-existing commitment had to be postponed.
Really, thank fuck.
“So~” the mentalist purrs as he lets himself fall on the comfy sofa, “wanna tell me why you invited me over tonight, my dear? And don’t tell me it’s for one of your sciency ojects-pray, Senku-chan, I know you are lying~” he winks at him, sending him a small mischievous smile when the younger boy’s mouth opens to protest, and Senku curses the mentalist’s incredible people-reading skills:
Fuck, he thinks to himself, feeling his palms sweat as he tries to come up with a lie on the spot, surprising him is gonna be impossible–
When Senku takes a second too long to answer, Gen’s playful smile dims as he frowns lightly, “Senku-chan? Is everything okay?” He asks sitting up and Senku tries to come up with anything, he really does… but he can’t lie for shit on a good day and now, mouth dry in anticipation and with a billion thoughts running through his brain, is even harder.
So, he folds: letting out a sigh and drying his sweaty hands on his pants, he smiles at the other, "Everything's fine, mentalist, calm down,” he murmurs, fondly rolling his eyes at the other’s worried expression, “I just got something I want to show you… and no, before you make a joke about my current face, I’m not constipated or anything, you trashy clown–”
When Gen’s worry gets washed away by the younger’s joke, Senku lets out an internal sigh of relief, “I don’t know Senku-chan, when you frown like that I can never tell~” he teases, blowing the shorter boy a playful raspberry when the young scientist hauls him up from the sofa by the hand, “Ah-ah, really funny, you bastard.” Senku hums rolling his eyes, but he is smiling, pulling Gen through the house and towards his bedroom.
He stops right before the door, lowering his gaze to look at the way the mentalist’s long, slender fingers interlock with his own and, when Gen curiously tilts his head, Senku takes a grounding breath; then, he opens the door, letting them in: it's safe to say that his room has not changed by much, messy and wild like it usually is, yet there is something displayed on his desk that instantly catches the older boy's attention, its misty surface glimmering in the low light, and the young scientist peeks at the other to assess his reaction.
Gen's looking at the object proudly standing in the middle of the otherwise empty desk curiously, somewhat drawn to it, so he leaves Senku's hand to step closer; when his eye land on the messily decorated label wrapped around the sealed flask and on the fuzzy, bubbly liquid inside—
He freezes, just a step away from it.
Senku swallows; then, he opens his mouth, whispering a hoping, gentle:
“Happy birthday, Gen.”
The idea had struck hm out of nowhere, a sudden glimpse of the night he confessed to the other boy now almost four months away, a fun conversation held in the middle of his living room surrounded by their family and with pointy birthday hats on their heads; he had wondered if he'd be able to recreate it and he had been happy when he had managed to.
The actual execution had been trickier than he had thought though, hell, it's like a bomb has went on inside his kitchen for how messy it is right now.
That's for future-Senku to worry about, though.
Regardless, he really hopes he managed to at least get close to the original taste since he had never personally tried one in his life, the only information he has on it being the mentalist’s vague description from months ago and a pretty non committal Google research.
Those damn royalties, he thinks to himself, doom is the World if everybody keeps legally owning information–
Still, when the mentalist’s hands wrap around the glass, Senku’s heart pumps faster.
Gen gently runs his thumb along the Senku's Oreo Cola written in the younger boy's messy handwriting, pausing only for a second on the black and white doodle of a chibi, familiar bunny in the corner of the label, before uncapping the hand-made seal around the top and bringing the flask to his lips, taking a quiet, silent sip.
When the older boy doesn't say anything for a long second, Senku finds himself speaking before he even realizes he's opened his mouth, "It's a gift, ya know? This morning I've found out that today is your birthday and I wanted to give you something, even if it's a bit of a last-minute thing…" he trails off, looking at the way Gen quietly puts the bottle back down.
The older boy's face is hidden by his hair, head tilted down slightly and precluding Senku from reading his expression, and the young scientist scratches the back of his head awkwardly, "I know it's not much but I remembered what you had told me on my birthday, about the Cola you liked, and I thought I could replicate it even if I have never even tried it before—"
Senku knows he is rambling, words spilling out of his mouth with no control as he tries to explain his thought process to the other, heart plummeting at the mentalist's reaction and feeling a sudden cold feeling of dejection fill his lungs, when—
Suddenly, two slender hands cup his cheeks and a pair of plump lips brush against his own, and Senku’s brain shortcuts.
The contact lasts less than a second, really, before Gen pulls away, and the look in his eyes has the young scientist's heart do a flip in his chest in a medically-concerning type of way; when the older boy speaks, his tone is so soft that Senku’s belly flutters:
“Thank you,” Gen says, cradling his face in his hands and smiling softly, “this is the most thoughtful gift anyone has ever given me, my dear, and I-”
The mentalist’s lushes tremble gently as his eyes fill with so much affection, and a sudden lump materialize in the young scientist’s throat, "Orry-say for not asking for permission beforehand, dear, but this was the only way I elt-fay I could convey my gratitude to you."
Gen's voice is a warm murmur that has goose bumps traveling down Senku's back, and the young scientist is entranced, his brain reduced to soft putty as the older boy continues, his beautiful gray, bright eyes veiled by a somber look of apprehension, "I'll tell you a little ecrete-say my dear… I don't really have the abit-hay to celebrate, for this specific ate-day brings back some emories-may I don't really enjoy, but…" he trails off, and the fondness in his eyes is so clear that Senku's heart explodes, "…but if it's with you, my dear Senku-chan, then I know it will be ectacular-spay."
Gen's voice is so soft, so warm that Senku feels overwhelmed by his own body's reactions, from the way his knees feel like jelly to the way his fingers twitch involuntarily, eager to grab, scared to touch, confused by the billion different stimuli he's been submitted to—
Until Gen's next words register, and Senku's poor, overstimulated brain violently brakes out of its daze making him suddenly perk up:
"So thank you, dear, and as I said, this was the only ay-way I could think of to repay you for this amazing gift, for all the ime-tay and thoughts you put behind this one beautiful, wonderful creation, a kiss as a thank you, and I—”
“Twelve.”
Gen, in front of him, blinks confusedly at his sudden interjection, mouth wide open around his interrupted thanks and looking like a fish out of water “...pardon?”
Senku licks his dry lips, looking straight into the older’s eyes and puffing his chest like some type of proud bird, “The one you had was my twelfth attempt, actually,” he murmurs, hyper aware of their closeness and of the way the older’s hands still brush the collar of his sweatshirt, “so I feel like you are missing quite a few… thanks still, mentalist.”
The implication hidden in his words is clear, and Gen’s face flames, “S-Senku-chan!” He screeches as his cheeks tint bright red, “Wha- Whe- Who taught you that!?”
Senku chuckles at the bashful reaction, sticking a pinky in his ear as he gives the other a small, mischievous smile, rasing a eyebrow in challenge; he is acting cocky like usual, but it's safe to say his ears are positively glowing red right now: Gen's right hand is still hooked around his collar, after all, and Senku can feel the mentalist's heat seeping into his chest, into his heart.
Right where it belongs.
Uh, he thinks to himself, observing entranced how Gen's lushes flutter as his beautiful gray eyes flicker downwards back to his mouth, I owe the big oaf a huge apology for all the shit I've given him—
His mind goes blank when Gen's plump lips connect with his own again making Senku's senses spike, and his eyes close after a second so to focus only on the warmth from the boy in front of him: their high difference is minimal really, since the mentalist is only a few centimeters taller than him, and this diversity is actually usually hid by Senku's own gravity-defying hair which add to his visual high, yet the small difference is enough for Gen's warm hands to raise back to his cheeks to angle his head up to kiss him better, and Senku's done for.
He has never kissed anyone before —nor he has ever desired to— and, for this reason, he finds himself with no solid idea of how he should act… but Senku Ishigami is a man of science, someone who one billion percent believes in the power of trial and error, so he does not hesitate: he lets Gen lead the kiss, yet he allows himself to explore the new data bombarding his brain.
Gen's manicured hands are scorching hot around his face, leaving a burning trail when they gently slide down his neck and around the nape of his head, and his lips are soft and plump and oh—
They are sweet, sweet like the Oreo Cola Senku has made him, and the younger's brain fries right there, standing in the middle of his room, in his mentalist's arms.
There's something extremely addicting in tasting his own creation form those soft lips, and Senku's positively gone: his hands, which had been hoovering just a second before, move out of pure instincts and gently wrap around Gen's waist, and, by the sound the mentalist lets out, the action is greatly appreciated.
This new position brings them even closer and Senku finds himself completely flushed against the older boy, his already fried brain stammering at the warm contact making him freeze where he is standing, and the small, endeared huff Gen lets out has Senku's face flame.
Holy shit, he thinks, blinking fastly when the mentalist leans back breaking the contact, no wait—
Senku's hands lock around the older boy's slim waist, pulling him back against him in a possessive but gentle embrace, and Gen laughs brightly at the dazed expression on Senku's face, "Oh my, dear," he giggles, softly cupping his boyfriend cheek in one hand and observing as Senku's eyes finally focus back on his face, "you really are naturally good at everything you do, aren't you, Senku-chan? I steal your first iss-kay sure than I can finally make you swoon, and yet I find out you already know how give me the erfect-pay kiss! Not fair~"
Senku's ears flame at the exaggerated, mischievous flattery, and he opens his mouth ready to tell the other off, when—
Wait a second, he find himself thinking as Gen's words register into his brain, blinking once, twice before he comes to the sudden, incredible conclusion that—
"Nope," he states, making Gen pause in surprise and tilt his head in confusion, "absolutely not, that was not even a millimeter good enough, mentalist."
When Gen frowns slightly in hurt trying to understand what he did wrong, Senku's hold on his hips hardens, rasing his hands higher to circle the mentalist's back and pull him flush against his chest, effectively bringing them back face to face.
Mouth to mouth.
"A single try is one billion percent not enough to be considered an extensive testing, so we absolutely need some more… sampling before we can even consider to be done here, mentalist," Senku whispers, smiling in victory when Gen's face flames at his words, "We have to try at least ten times more, and then change a few variables here and there, test and re-test even previously tried roads, you know? It's all about statistical significance, after all: we wouldn't want to leave anything to chance, right mentalist?"
The bashful surprise on Gen's eyes is one billion percent real, yet the title of greatest mentalist who ever lived he carries on his shoulder is not an exaggeration, and Senku sees, front row style, how the endeared, embarrassed tilt of Gen's brow turns mischievous as the older boy taps his index finger on Senku's chest, right where his beating heart rests, "Oh my, my, you really are a little science gremlin, aren't you, my dear?" He chirps, theatrically bringing his hand to his head in a dramatic flare of limbs, "Admit it, this whole thing was actually a way for you to collect ata-day and test your hypothesis, oh, how will my poor heart survive this—"
This guy, the young scientist thinks, rolling his eyes fondly as the mentalist keeps running his impish mouth, is so ridiculous, jeez, what did I get myself into—
So, Senku kisses him to shut him up.
“Happy birthday, Gen!”
Their cheerful celebration echoes in the small private restaurant room they had booked –even if said room it’s just a small party area in the back of Yua-san and Yato-san’s ramen shop the Ishigami’s love so much– and everybody claps their hands when Gen blows the candles on his cake out.
When his father –damn old man– hugs the mentalist to his chest into an affectionate, fatherly hug, Senku rolls his eyes fondly, chuckling loudly when Lillian gives his boyfriend an embrace of her own; when Gen’s get roped into a series of cheerful hugs from Yuzuriha and Taiju as well though, Senku frowns slightly, “Alright, alright, you are done here now big oaf, stop ogling him,” he says, shooing his best friend away and finally getting closer to his boyfriend.
Meeting Gen’s bright eyes, Senku feels a soft smile pulling on his lips as he grabs his hand, “You done partying now, you diva?”
The mentalist pouts childishly at his words, "Meany, Senku-chan is such a meany! Saying these things to me even after he insisted so much to elebrate-cay!"
Senku shrugs, wrapping his hands around Gen's waist to pull him into a quick, soft hug before parting, ears tinting slightly when the mentalist bashfully smiles at him: neither of them are particularly into PDA, preferring to leave their more affectionate moments for when they are alone, yet the softness of their relationship is not lost to others and Byakuya whistles loudly, making Senku snap his eyes to his dad with a grunt of drop it, you old man, we are having a conversation here—
The mentalist giggles, "I'm ever so glad I listen to you, my dear, for this arty-pay is simply wonderful!"
Gen, like he had told Senku a few days ago, does not usually celebrate his birthday since it falls on the Fist of April, a cause of teasing and incredulity in his younger years and then disbelief later on when he because famous as a mentalist, yet Senku had comforted him by reminding him that his new family would have loved to celebrate with him, celebrate him, and Gen had smiled hopefully in the embrace of Senku's arms, fishing his phone out to send out invitations.
It had been rather funny how, literally thirty-seven seconds after the text had been sent, Byakuya and Lillian had called from oversea to wish the boy a happy birthday in a frantic conversation of we are so sorry dear, we had no idea—
Still, in the end that had decided to celebrate the following Saturday by enjoying a warm cup of ramen at Yua-san and Yato-san's shop, carrying colorful, wrapped gifts and having a sweet, creamy cake as dessert.
Gen had thanked them incredulously when his family had handed him his presents; the boy usually would have oped them once he'd gotten back to his own house as etiquette dictates, yet his friend's hopeful faces had him unwrap the pattered papers of the gifts, and his expression had been absolutely beautiful:
Yuzuriha had gifted him a hand-made embroidered shirt, the white fabric acting like a canvas for the colorful lines of blues, purples and indagos decorating the fashionable piece with elegant twirls, and Gen had promised her he would wear at his next show making the girl blush to the root of her hair, while Taiju had made him a beautiful, colorful clay pot for your cactus Togatta-chan! You told me you needed to re-pot it so I made you a bigger vase!— that had Gen smile kindly at the taller boy, ever so surprised that the brunette remembered what he had told him about his collection of houseplants.
It will never stop being funny to Senku how the big oaf has developed a passion for pottery during one of his and Yuzuriha's arts and crafts dates, his big frame and dense head somehow so far away from the concept of delicacy and carefulness usually associated to the art, and yet here he is, making hand-made pots for his friends.
Never change, you big, softy oaf.
While his friends had decided to do solo-presents, the old man and Lillian had joined forces to gift the mentalist a pair of beautiful silver cufflinks in the shape of a crescent moon, and both Gen and Senku had blushed when Lillian had added this way you guys match since this pair partners beautifully with the one you own, Senku!
In the end, the celebration had been wonderful, just like the mentalist said.
Gen hums, leaning into Senku's shoulder as he observes their happy family with his sly eyes, chuckling lightly at the sight of Taiju and Byakuya's terrible attempt of cutting the cake into equal sized slices, "…I'm ever so glad I istened-lay to you, my dear, I am having a lot of un-fay today."
Senku smiles at the words, carefully but surely wrapping one arm around the other's shoulders as he answers, "I told you they would have been ecstatic, mentalist… and now you have no more excuses to dodge any future celebrations, alright?" He murmurs, before holding his own chin between his fingers and looking up, pensive, "Well it's gonna be hard for you to anyway, considering that our anniversary falls on the same date as your birthday now."
Gen, next to him, blinks astonishingly before turning to face him better, clearly taken aback, "What— it does?"
Senku shrugs once, "Well isn’t the day you kiss your anniversary, usually?” He asks as he sticks a pinky in his ear, “That’s how it works, am I wrong?”
When Gen’s eyes bug out, Senku just tilts his head.
“Senku-chan,” the older boy starts, “I thought the two of us were already ogheter-tay before then, were we not?” Gen wonders, curiously looking at him, and Senku tsks, “You are the love expert here, you bogus magician, that’s why I am asking you.”
At the boy's deadpan, Gen smiles softly, if not a bit exasperatedly, "Well, I uppose-say there is no right nor wrong way to decide that… yet Senku-chan has just said the utest-cay thing ever! My kiss was so erfect-pay you want to commemorate it!" He chirps, demurely covering his small teasing grin behind his hand, and Senku rolls his eyes fondly, "Shut up, it's the most logical way; also this way there is no escape for you, you bogus mentalist, next year we will one billion percent have to celebrate on the right date!"
The mentalist smiles softly at that, "Next year, eh, Senku-chan? Are you planning to keep me around for that ong-lay? How lucky I am~"
Gen's tone is light and teasing, but the hopeful, endeared timbre of his voice is not lost to Senku, so the young scientist smiles brightly to him, holding his hand tightly, "Well said mentalist, one billion points to you!" He exclaims, before looking into Gen's beautiful eyes and adding a soft, "I already told you: you are mine now, and I have every intention of keeping you with me because there is no one better than you to be at my side on this planet."
For how sappy these words are, he still means every single one of them from the bottom of his traitorous beating heart, and he truly wants the mentalist to believe him, and…
Well.
By the way Gen grabs his cheeks and pulls him into a tender, breathtaking kiss, Senku guesses the message has been received loud and clear.