Posted originally on the Archive_of_Our_Own at https://archiveofourown.org/
works/954286.
  Rating:
      Explicit
  Archive Warning:
      Underage
  Category:
      M/M
  Fandom:
      Free!
  Relationship:
      Hazuki_Nagisa/Ryugazaki_Rei
  Character:
      Ryugazaki_Rei, Hazuki_Nagisa
  Additional Tags:
      First_Time, Plot_What_Plot/Porn_Without_Plot, porn_porn_porn, Established
      Relationship
  Stats:
      Published: 2013-09-04 Words: 4141
****** Research and Experimentation ******
by kfisk8r
Summary
     After months of dating and fooling around, Rei and Nagisa are finally
     ready to go all the way. As with anything he takes an interest in,
     Rei enthusiastically researches the various sex acts they could do
     together if they wanted to take that final plunge. He comes to a
     rather interesting conclusion...
Notes
     This fic is a thank-you for the outpouring of love for "Beautiful
     Together". They're both stand-alone, but this could definitely be
     seen as a sequel if you like. Please enjoy the smut! I had a lot of
     fun writing these two again :)
Maths and sciences had always been Rei's favorite subjects. There was something
comforting about being able to know, absolutely, that there was a correct
answer to be found among the data and calculations. One had only to master the
underlying concepts and apply them to a given problem in order to come to a
concrete and dependable answer. But today, in an unassuming classroom in
Iwatobi High School, he found his mind drifting from the formulas and
variables. Today was special. Today, he was going to...
 
“Ryugazaki-kun.... Ryugazaki-kun!!!”
 
“Ah, yes!”
 
“The answer to question 12, please?”
 
Rei looked down at his paper of half-finished physics problems to find the
answer to question 12 conspicuously missing. He could feel his ears turning
red. “S-sorry, Ishikawa-sensei...”
 
Once the hushed murmurs of the class had died down, the mousey woman behind the
teacher's podium sighed. “This really isn't like you, Ryugazaki-kun. Please be
sure to take care of whatever it is that's troubling you before the next
class.”
 
“I promise, I will,” Rei said. The bell rang out, as though it understood his
plight and wanted to save him from further embarrassment. He gathered his
things quickly, packing them into his backpack and slinging it over his
shoulder before hurrying from the classroom. He knew it was just irrational
paranoia, but he couldn't shake the feeling that if anyone were to talk to him
or look at him hard enough, they'd figure out what he was about to do... Or
rather, what he and Nagisa were about to do... Together.
 
They'd been dating for approximately six months, and in that time, the two had
become progressively more intimate. Rei had never really thought much about sex
before, except how messy and clumsy it might be, until he and Nagisa had become
romantically and physically involved. Nagisa had shown him that there was more
to physical intimacy than the traditional act of penetrative sex. They'd done
just about everything—kissing, hand jobs, dry humping, heavy petting, and most
recently, oral sex. And all of it had felt fantastic. As with anything he took
an interest in, Rei began researching the various sex acts they could do
together if they wanted to take that final plunge.
 
What he'd found in his research was both arousing and frightening. It turned
out they'd only seen the tip of the proverbial sex iceberg. With such a wide
array of possibilities available, he'd done his best to narrow down their
options to the few that were suitable for absolute beginners. He'd attempted to
account for all of the variables: age, athleticism, pain tolerance, genital
size... In the end, he'd come up with a solution that he believed would be
mutually equitable. Naturally, he'd done some testing just to be sure, but...
 
“Rei-chaaaaaan!” A blond head bounced between the students making their way out
of the school's halls and into the crisp December air outside. Despite his
nervousness and embarrassment at being caught daydreaming in class, Nagisa's
enthusiasm still brought a smile to his face.
 
He was almost prepared for the weight of the shorter boy jumping onto his
shoulders from a meter away. Lurching under his burden, Rei put up his
customary protest. “Nagisa-kun, please! You're deceptively heavy for someone
your size, you know.”
 
“Sorry, Rei-chan,” Nagisa said between giggles, slipping down to the floor and
wrapping his arms around one of the taller boy's. “How was class? Learn
anything exciting?”
 
Rei spluttered, looking away to hide the blush on his face. How could he admit
to being so preoccupied with their after-school activities that he couldn't
even concentrate in class? “Well... It was mostly review, so...” He adjusted
his glasses.
 
“Review, huh,” Nagisa said, stretching his neck to get a better look at Rei's
face. Apparently satisfied with what he saw there, he straightened, a soft
smile playing over his lips. “It's okay... I had trouble concentrating all day,
too.”
 
A shiver passed through Rei as their eyes met over his glasses. Nagisa was
constantly surprising him with his powers of perception. His original
impression of the boy was that he paid only enough attention to make it through
any given situation onto the next. He'd revised this theory as he observed
Nagisa around the other members of the swim team. The blond was always finding
little ways to cheer people up if they were down, or mend fences if someone got
offended, or (most recently) get Haru-senpai and Makoto-senpai to realize their
glaringly obvious feelings for one another. Rei smiled back, his fingers
slipping through Nagisa's of their own volition as they made their way to the
train station.
 
–-----------
 
“You're sure your parents won't be back tonight?”
 
The two teens dropped their backpacks on the way into Rei's immaculately
organized bedroom. “Not until Monday. They left for Tokyo this morning.
Apparently there's a big conference going on for dad's company and he's a
keynote speaker. We've got the house to ourselves...” The words hung thick in
the air, full of uncertainty and expectation. Rei placed his shaking hands on
his desk chair and took a deep, calming breath.
 
Slender arms wound their way around his torso from behind as Nagisa pressed his
forehead into Rei's shoulder. “Hey, we don't have to do anything you don't want
to do, okay?” The shorter boy gave him a comforting squeeze. “We can just have
dinner and watch those dorky physics documentaries, then gorge ourselves on ice
cream until we pass out. There's no pressure.”
 
His heart thumped hard at his ribcage. It was true, there really was no
pressure to go through with anything other than their normal routine. But it
was Nagisa's consideration, his sweetness, and his ability to push Rei out of
his comfort zone without taking things too far that had him all the more
excited to take this step with him. He turned to look down into kind eyes,
taking the smaller boy's round cheeks in his hands and kissing him thoroughly.
Heat was already beginning to pool low in his belly, even before Nagisa opened
his mouth to deepen the kiss. When he pulled back, they were both breathing
heavily, pink staining the edges of their cheeks. He'd been anticipating this
all day... All week. Possibly his whole life. Like hell he was going to back
out now. “No, I want to.” He pressed closer, relishing the pressure of Nagisa's
hipbone against his hardening dick. “I really want to...”
 
The corners of Nagisa's mouth turned up in a knowing smile, his eyes twinkling
with an air of excitement and mischief that belonged only to him. He grabbed
Rei's belt, yanking their hips together as he ground against the taller boy,
and leaned up to nip at a reddened earlobe. “Then what are we waiting for?”
 
They made short work of each others' clothes, ties and jackets and shirts
falling in a trail leading to Rei's bed, where he sat, pants and boxers around
his ankles. A hot, slick tongue trailed its way from his neck to his right
nipple, where Nagisa began to suck as he eased himself out of his own pants.
“So how did you want to do it,” he asked, kissing his way down sculpted abs.
“With me on my back and you in between my legs?” He paused, skirting his way
around Rei's dick to tease at the sensitive skin over the hipbone. “Maybe
doggie style?” He pressed his tongue into the base of Rei's cock, licking
slowly up to the head, then fixing him with a questioning stare.
 
Rei took a shuddering breath and swallowed. “A-actually... I did some r-
research... And I think it might be best if I were to... Ride you.”
 
“... Eh?” Nagisa's eyes were impossibly wide. He jumped up, only to realize
that his pants were still around his ankles, and careened onto the bed, half on
top of Rei. They laid there, a tangle of limbs and mostly removed pants,
staring at each other awkwardly for an interminable amount of time.
 
“I-I mean, not that I'm going to complain or anything! I just thought...” Rei
had never seen the younger boy so flustered. In a way, he was almost proud of
himself. “Well, you know, you're... Taller?”
 
“... Taller?” It took several moments for that particular bit of information to
process. But once it did, Rei's stomach began to quiver. The shaking progressed
up through his chest and into his throat where it emerged as a raucous,
uncontrollable laugh. He flopped back onto the bed and covered his face, wiping
at the corner of his eye where a tear was forming.
 
“Rei-chan, you jerk! Stop laughing at me!” Nagisa slapped him half-heartedly
across the chest, but it just made him laugh harder.
 
When he finally moved his hands and looked at the Nagisa, the other boy was red
to his ears and pouting up at him. “S-sorry,” Rei said between chuckles, “it's
just... You've been reading your sister's yaoi manga again, haven't you?”
 
Nagisa hid his face against Rei's chest. “I wanted to make sure it was good,
'sall. And the taller guy always does the smaller one, so I just thought...”
 
Wrapping his arms around slim shoulders, Rei buried his face in the smaller
boy's wild blond curls and hugged him tight. “It's okay, really. Even though
manga isn't a very reliable depiction of real life, I suppose it was just your
way of doing research.”
 
“That's right,” Nagisa said, relaxing against him. “So, Mr. Research,” he
propped himself up, fixing Rei with an expectant glare. “How did you come to
your conclusion that I should do you instead of you doing me?”
 
“W-well,” Rei started with a nervous gulp, “I'm definitely the more flexible of
the two of us, which is necessary for being on the receiving end. In addition,
since I'm larger in build and your um... Equipment... Is slightly shorter than
mine... It minimizes the risk for potential internal injuries.” He could feel
his face heating with every point he made.
 
But rather than poke fun at him for his compulsive attention to detail, Nagisa
simply listened, brushing a stray lock of hair away from his forehead. “Mm-
hmm... Makes sense. Was there anything else?”
 
Rei hesitated. “Yes, well...” The repeating pattern on the ceiling tiles
suddenly became very interesting. “N-naturally, research couldn't account for
all of the factors, so... I did a little... Experiment...”
 
The fingers combing through his hair twitched, then stilled. Nagisa's face
filled his field of vision. “What kind of experiment, Rei-chan?
 
How could he possibly tell Nagisa what he'd done on his own? It was
embarrassing... It was weird... It was...
 
Pain shot through his cheek as the younger boy pinched him. “Don't go over-
analyzing this! I know how you get. No need to be embarrassed, just tell me,”
Nagisa said, kissing the spot where he'd pinched to soothe the burning skin.
 
Rei took a calming breath and cleared his throat. “I wanted to know how it
would feel... So... I used my fingers to simulate being penetrated...”
 
Unusual pink eyes glimmered in the waning sunlight streaming in through Rei's
window. “You fingered yourself...” Nagisa's breathing accelerated, his hips
starting to rock against Rei's sculpted abs. “And? What were the results of the
experiment?”
 
His dick twitched against the smaller boy's thigh as he took up the rhythm. “It
was... very stimulating. However, ultimately I would rule the experiment
inconclusive...”
 
Nagisa pressed a kiss into his neck, grazing sensitive skin with his teeth.
“Oh? Why is that?”
 
Rei let his hands wander, enjoying the play of smooth skin over hard muscle as
they moved against one another. “A-as the book suggested, I slowly made my way
up to three fingers... But... I still wanted more...”
 
There was a sudden shuddering rush of air against his neck, accompanied by a
shiver that shook through Nagisa and into him. Without any attempt at pretext,
his mouth was taken in a kiss unlike any he'd had before. Teeth clicked,
tongues fought, fingers scrabbled against his shoulders just shy of causing
pain. Nagisa let out a sound somewhere between a grunt and a whimper as he
attempted to pull Rei's tongue as far into his mouth as he could without
actually detaching it. By the time they parted for air, they were both panting
and shaking, bellies smeared with precome. “Show me.”
 
The next minute or so passed in a dreamlike state. Blood rushed hard in Rei's
ears as they rid themselves of their lingering clothes, and as he leaned over
the bedpost to open the top drawer and retrieve a garish blue and pink bottle
he'd bought at the corner store with his hat pulled over his eyes. Nagisa
dutifully spread a towel over his bed. Even in this, he couldn't abide a sticky
mess on his clean comforter.
 
The other boy was unusually silent, kneeling between Rei's spread legs and
watching patiently, but with an edge of anticipation written plain across his
usually soft features. If Rei had to label the emotion, he'd call it hunger.
 
Fumbling hands opened the lube bottle, squirting a dollop of clear viscous
fluid onto waiting fingers. Rei held his breath and reached down to hold his
balls out of the way and expose his tight entrance, his lubed fingers making
their first tentative circle around the wrinkled pucker. His dick jumped at the
tickling, electric feeling as he exhaled with a shudder. Nagisa gripped his own
cock hard, mirroring Rei's breathing as he watched, fascinated.
 
He took his time, playing at the edge of the little hole in order to make it
open up on its own. In his first attempt, he'd gotten overzealous and pushed
his finger in too early, a mistake he didn't intend to repeat. Gradually, the
tip of his finger began to slip further and further into the softening flesh.
When it popped past the first ring of tight muscle, his knees lolled to either
side. However the soft, “Ah,” that rang through the quiet room came not from
him, but the blond kneeling between his legs, face flushed and lips parted in
pleasure. He wondered if he looked as beautiful to Nagisa as the other boy did
to him.
 
The second ring, the gateway to the silky, pliant sheath inside, was tougher to
breach than the first. He circled his finger, applying more and more pressure
until it yielded, and his finger sank in to the knuckle. This time, it was
Rei's moan that broke the silence.
 
Nagisa thrust into his fist, matching the pace of Rei's finger which was slowly
pumping in and out of his loosening hole. “That's... So hot, Rei-chan... Better
than anything in my sister's manga...” His eyes flickered between Rei's face
and his exposed ass. “How does it feel?”
 
His finger emerged from the winking hole and was joined by a second, repeating
the whole process anew. Rei focused hazy eyes on Nagisa, trying his best to
control his panting breaths. “G-good... Strange, but very good.” The second
finger slipped in and he gasped as the strong muscle clenched around it.
 
Strong fingers wrapped around his wrist, stilling him. “Let me... I want to
feel it, too.” Rei's dick throbbed in agreement.
 
“Okay,” he said, passing the bottle over to Nagisa. “But use this, and go
slow.”
 
“I promise,” came the enthusiastic reply. The blond squirted an indecent amount
of lube onto his fingers and brought them Rei's already slick opening,
massaging the brown-pink flesh with the utmost care.
 
His index finger slipped in almost instantly, leaving both of them gasping. He
pulled it most of the way out and pushed in again, and this was different
somehow than when Rei had done it by himself, more intense, deeper. He writhed
with it, biting back a whimper.
 
“Is this okay? It went in so fast...” Nagisa's voice was thick with awe and
arousal, his finger stroking deep inside in a place where Rei hadn't yet gotten
on his own. It was too much. It wasn't enough.
 
“M-more... Nagisa-kun.” When the finger left him, he whined. His left hand
began to move of its own accord, rubbing the base of his dick as he awaited the
next onslaught of sensation. This time, two fingers pressed at his hole,
wiggling gently until they both worked their way in.
 
“It's so soft,” Nagisa said, breathless. He worked his way around, pressing and
exploring, pushing and retreating, until Rei's hips began to chase after his
fingers, eager to keep the feeling of fullness and pressure from escaping. “I-
I'm... supposed to get to three, right? Will they fit?” His voice shook, and
Rei looked down to see the younger boy jerking himself off, his dick straining
and red against winter pale skin.
 
“Just... Do it... They'll fit,” Rei said between gasps.
 
The wait was agonizing, the third finger stretching the sensitive skin to a low
burn as it pressed its way past one, then two layers of muscle into Rei's ass.
“Wow... It's so hot, Rei-chan... And tight...” Nagisa swallowed, the unspoken
understanding that it was his dick that would be in there next hanging heavy
between them.
 
And Rei wanted it, wanted to feel what it would be like to have his hole even
fuller, to feel Nagisa's heartbeat from inside his own flesh. He ground against
the fingers slowly pistoning into him, feeling Nagisa's knuckles stretch him as
those slender fingers reached inside and stroked.
 
Something electric sparked deep in his gut, and he jackknifed off the mattress
with a choked cry. Nagisa pulled his fingers out abruptly, leaving him empty in
their wake, his cry fading into a frustrated whimper.
 
“Rei-chan, are you okay?!” Sticky fingers slipped against his shoulder as the
smaller boy shook him, brows drawn together in concern.
 
“C-calm down... I'm fine.” He took Nagisa by the shoulders, sitting up and
pushing the other boy prone. “I think I'm ready.”
 
“Oh... Oh...” Nagisa turned and flopped down, arms behind his head, unable to
hide his excitement. His prick stood proud and wet, and he smiled up at Rei
through the blush on his face.
 
Rei rummaged in the drawer and emerged with a square packet, tearing it open
with his teeth when his trembling, slippery fingers failed him. He pinched the
tip just like he'd learned, and rolled the condom over the blond's cock, making
sure to get it all the way down to the base. He doused it in lube just to be
sure. The book said you could never have too much. A soft snort, followed by a
high pitched giggle broke his concentration. He glared down at the smaller boy,
eyebrow beginning to twitch. “... What's so funny?”
 
“It's the same face you make when you're studying really hard. You're just so
intense... It's really cute,” Nagisa said, leaning up to steal a kiss. “I'm
usually the eager one, so I thought it was funny that you were so excited.” His
hands gripped Rei's hips, guiding him to straddle the smaller boy. “Come on...
You want to do it, right?”
 
Rei nodded, mortal wound to his pride averted, and swung his leg over Nagisa's
thighs.
 
“Then ride me.”
 
Rei sat back, feeling the thick hard pressure of Nagisa's dick against him. It
was like standing on the edge of a cliff, wondering if he was about to plunge
into a deep ocean or crash on the rocks below. He'd never know if he didn't
jump in the first place. But it seemed like the more he pushed, the harder the
pressure got without actually breaching the waiting hole. Suddenly, he felt a
popping sensation, and Nagisa's face contorted into a pained grimace.
 
“Ow, ow, ow! I think my dick got bent there for a second!” Sure enough,
Nagisa's cock now rested in the crevice of Rei's cheeks, curving up toward the
small of his back.
 
“Ah, s-sorry,” Rei said, lifting himself up to readjust. “Are you okay? Can we
try again?”
 
“Yeah, hold on,” Nagisa said, reaching down between them. His fingers searched
out Rei's entrance, grabbing his dick and guiding the head to rest snugly
against it. “Okay. I think it'll work this time.”
 
Breathing deep, Rei sat back. The pressure felt different this time, stretching
him, rekindling the dwindling fire in his abdomen. When the flared hood of
Nagisa's cock finally pushed past his sphincter, it burned. More than three
fingers, more than he'd possibly anticipated. But beneath the pain, there was
the promise of a blinding pleasure. They shook against one another, breaths
shallow and trembling, wide eyes locked in awe.
 
“T-tight...” Nagisa's hands fluttered their way to Rei's waist. “Is... Is it...
Okay?”
 
Rei nodded, face fever-hot, voice failing, sweat dripping in rivulets to pool
at the small of his back. Bracing himself on the smaller boy's shoulders, he
sank down an inch. Lifted up. Sank down further. Nagisa throbbed inside him and
they both moaned.
 
Rei swore the younger boy's cock was of average size, but it felt absolutely
enormous crammed inside him. It seemed to take forever to work his way down to
the base. When his ass finally made contact with the firm muscle of Nagisa's
thighs, he sighed in relief, breathing his way through the unnerving feeling of
fullness and his body's attempts to expel the intruder.
 
“It's so good, Rei-chan... You're so good...” Nagisa's hands traced the
contours of Rei's abs, brushed over peaked, sensitive nipples.
 
Rei gasped, his hips making their first, tentative sway. Nagisa's name ghosted
past his lips in the rush of pleasure that followed. They moved together in
awkward starts, learning a timeworn rhythm with each hitched breath and moan.
As their thrusts gained tempo, Rei became bolder, angling his hips, searching
for that spot that Nagisa had grazed with his fingers before.
 
The further he leaned back, the more the pressure built in his belly, his dick
leaking a steady stream of clear precome as it bounced against the blond's
stomach and his own. It had to be close... He reached back, bracing himself on
strong forearms, and arched up, then dropped down...
 
“Ah!” The pleasure was blinding, shooting through him like electric current.
“Yes! There!”
 
“Fuck... You're so beautiful like this, Rei-chan...” Nagisa dug his heels into
the mattress and thrust up, striking that spot again, bringing forth a choked
cry. Emboldened, he grabbed Rei's dick and began to stroke leisurely as he
fucked up into him.
 
“N-nagisa!” The last vowel drew out, pitch escalating as the younger boy took
full advantage of their new angle to drive Rei further and further toward the
oncoming precipice. “I can't... I'm going to...”
 
“Me, too,” Nagisa said, voice tight in his throat. “Let's go together...” The
wet sound of flesh slapping flesh punctuated the rising cries of pleasure from
the two boys as they neared their peak. With one final push, Nagisa's head
tipped back, mouth open in a rough scream as he filled the thin rubber sheath
separating his dick from Rei's ass.
 
Rei followed close behind, shooting ribbons of cum over the younger boy's chest
and neck as the hard cock inside him pulsed at his prostate, milking him. He
slumped, sated, against Nagisa's smaller form, smearing the sticky fluid
between them, not even caring about the mess they'd have to clean up later.
 
As their breathing slowed, Nagisa petted Rei's hair, neck, and shoulders,
murmuring praise and thanks in his ear, showering his cheeks and eyelids with
soft kisses. He returned some of them, grimacing through the discomfort as the
blond's softening dick slipped from his abused hole.
 
“Whoa,” Nagisa said, marveling at the full condom as he rolled it off carefully
and held it up for inspection. “I came a lot! It was like you were squeezing it
out of me...”
 
Rei hid his redding face in the crook of his elbow. “Don't talk about it like
that...”
 
Nagisa giggled. “And you're back to being your usual embarrassed self.” He
plopped down next to Rei, taking his wrist and peeling his arm away from his
face to place a playful peck on the tip of his nose. “It's okay. You're
beautiful no matter whether you're embarrassed or all hot and wild.”
 
He bounced over to his backpack, naked and unashamed, and rifled through it,
coming up with a disgustingly pink book, a blushing and overly effeminate boy
being molested by a tall and masculine man on the cover. Flashing the “V” for
victory, he grinned, mischief written plain across his face.
 
“So,” he started, jumping onto the bed with his legs crossed, looking for all
the world like this was an elementary school sleepover and not a couple of
high-schoolers doing naughty things while their parents were away, “what do you
say we order some pizza, then I show you what I learned from my research?”
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