Archive of Our Own

When exactly the mutation began, Izuku did not know. All he knew were the tales of Alpha and Omega’s who could hardly breathe during their cycles, writhing in agony upon sweat-clad sheets as they begged and pleaded for someone, anyone, to put them out of their misery - whether it be through death or orgasms, they did not care.

Heats and ruts weren't always something to fear; rather, it was a period of time when one focused on their personal needs.

A time during which self-care trumped all else.

But then the unbearable ache appeared; it was not a common condition, it was not something which troubled many, but everyone was warned about the possibility of it happening before they presented. The tales of it were almost used to frighten children, to warn them about what was to come, about what they needed to prepare for.

The pills were created shortly after - medicine specifically designed to assist those who couldn’t bear to be present and lucid during their cycles.

Izuku simply thought they were nothing short of glorified, over-priced sleeping pills, but he did not know the effect they had on those who chose to take them. Since his heats were fairly regular, pain free, he didn’t understand how the medicine worked.

Yet he understood the desire for relief, he understood why someone would much rather sleep for 12 hours, their temperature lowered and hormones stabilized, rather than deal with excruciating pain. It was easier, simpler to take the pill, sleep, and in between the intervals, have an orgasm or two, eat and drink, while crying, chirping and chuffing for a mate that would never come, and take another pill before going back to hibernation.

Kacchan did not keep his own condition a secret, he never attempted to convince anyone that he was not one of the Alpha’s forced to go through this shit every few months when his rut hit, yet no one in his class knew about it - no one except for Izuku.

Because of course he knew.

Izuku knew everything there was to know about his Kacchan, whether the information was given to him voluntarily or taken through whispers in the hallways and texts read on stole- borrowed phones.

But all of his other findings - the ones about his quirk, his diet, his sleeping schedule, his apparent closeness with his Middle School friends, even his damn skincare - those were carefully researched, purposefully sought out, while this was something he’d found out purely on accident, back when they did not speak to one another and Izuku so rarely had an excuse to go to Kacchan’s home.

It was several years ago that it happened - Katsuki’s presentation as an Alpha, something that did not surprise Izuku one bit.

With both of his parents being of the subgender, it was to be expected that Katsuki would turn out every bit of Alpha that Masaru and Mitsuki were. It was even expected of him to present early, which he did - the first in their school year.

Auntie Mitsuki came to visit his mother that day, face tired and filled with pride all at once, and while he was scrolling on his phone and the two women were sitting on the couch, sipping their tea, he heard the blonde make an offhand remark, something that shouldn’t have gotten stuck inside his head but it did anyway.

“Ah, fuck, I have to go pick up Katsuki’s rut meds - his rut is coming up and the brat can’t make it through without them, ended up in the damn hospital the last time, back when he was presenting.”

The second she had left, Izuku had excused himself and rushed to his room, doing what he always did whenever he found out new information about Kacchan - with shaking, excited, hands, he’d written it down into one of his many notebooks, into the newly created section dedicated to Katsuki’s rut cycle.

The date of the first one he had, the notes of his scent that Izuku had only caught the slightest hints of, and now the medication which he quickly researched, medication designed for difficult and unbearable ruts.

Of course, none of this mattered to him. The notes, the curiousity, the lingering stares, they were all harmless.

All he was gaining was new information about Kacchan, and it did not matter he knew about his ruts. And so, after confirming it was not life-threatening in any way, he moved on and pushed it to the back of his mind.

Well. Maybe he was a little bit curious if Katsuki’s harsh ruts were affected because of the chemical imbalance his quirk caused, and maybe he wondered if his Alphan hormones were stronger or more powerful, but that was it! And, maybe he, sometimes, when he caught him in pre-rut, wanted to ask him if he had his meds with him, if he was ready for his rut, but that was just what any good friend would do - he never wanted Kacchan to be hurting while in such a weak, vulnerable state.

But, other than that, it wasn’t important.

That was until he, himself, presented as an Omega.

Despite the lateness of his presentation that filled him with nervous energy, the negative emotions were immediately replaced with excitement - his desperate desire to fit into the rest of the pack would finally be able to be fulfilled.

It happened in the midst of their second year, when the anxieties of what would happen to them had already vanished with the disappearance of the League, and they slowly began to relearn what it meant to be teenagers, normal students with relationships and friendships and pack bonds that couldn’t be replaced.

After a calm heat he had spent with one of Kacchan’s stolen tank tops pressed to his nose, he had exited his room, freshly showered and a smile tugging on his lips as he rushed down the stairs. No matter his excitement, however, he knew it was as uneventful as every other presentation that had occurred during their past two years of studies at UA.

He was an Omega, one of the handful in their class, and that was that.

When he arrived downstairs, the class only congratulated him, asked if he needed anything of theirs for his new nest, and they moved on with their lives, as if nothing had happened or changed at all.

And there lay his problem - they all moved on.

It was irrational, stupid and childish of him, but for some goddamn reason he was yet to understand, when Katsuki simply hummed in acknowledgement, sparing him nothing but a fleeting glance before he turned towards the sheets of homework he was working on on the coffee table in the common room, not even offering so much as a damn T-Shirt for his nest, Izuku had to dig his nails into the palms of his trembling hands to stop himself from punching the Alpha in his stupid handsome face.

His newly presented Omega whined and cried pitifully as that familiar scent of gunpowder and firewood filled the air, and yet there was not a single hint of desire within it.

There was nothing there. Nothing at all.

For a brief moment, Izuku almost convinced himself that, maybe, Kacchan simply had better control over his scent than most and he was hiding his true feelings.

But then he remembered the joy, the comfort and happiness that uncontrollably bloomed within his natural perfume whenever he was with his friends, his pack, and he bristled.

Even with his newly developed cunt and the notes of strawberries and homemade cookies emitting from his glands, Kacchan still didn’t see him as a potential mate, didn’t even care enough to breathe in deep when Izuku walked into the room.

And that was a new thought, an unexpected one, one he’d never even realized was something he actually wanted.

He never considered the fact that he might’ve been viewing Kacchan as a mate, or as someone who would become his mate at the end of the line, nor did he think the need to know everything about the Alpha was a byproduct of his emotions - desire mistaken for admiration.

Finally, all of those strange feelings of annoyance whenever someone other than himself was close to Kacchan, the tingles and goosebumps when Kacchan touched him, the thoughts of holding his hand and kissing him breathless while they lay underneath the sheets, they all made sense.

Everything clicked into place.

And yet it did not matter one bit, not at all, because Kacchan didn’t look at him that way - he didn’t trail his gaze over his body, he didn’t breathe in deeper and deeper and deeper until Izuku’s scent was embedded into his very lungs, and he didn’t care about him in that way.

He never would.

But that was fine! Izuku didn’t care about that; he had lived without Katsuki’s affections for so long, he could continue to do so.

Finally, after years of animosity and arguments, they were getting along, and Izuku couldn’t lose that, he simply couldn’t. They were friends, truly and undeniably friends who spent time together outside of the obligatory training - they walked into each other’s rooms, ranting and venting about whatever came to mind, they sat on each other’s beds and their arms and legs touched as they watched movies, they talked, and they didn’t hate each other. And, maybe, during some of those moments, Izuku caught Katsuki’s eye, and thoughts lingered inside his head, thoughts which were now viewed in a much different light - maybe there was a chance that beneath the friendship hid something more.

Still. He couldn’t risk it, no matter his suspicions, he needed his Kacchan by his side.

So, who cared that Izuku wasn’t hanging off of his knot every second of every day like he thought about when his fingers trailed beneath the waistband of his shorts in the late hours of the night? Who cared that Kacchan wasn’t sleeping beside him in his nest where he belonged and, instead, Izuku was forced to steal his sweaty clothing and pretend as if he didn’t know what the hell Kacchan was talking about when he kept asking where his clothes went?

It was fine.

All he had to do was ignore the nagging and whining his Omega seemed determined to keep up and it would all be fine.

But, of course, Kacchan had to go ahead and ruin it for him.

Izuku already knew Katsuki’s cycle in an embarrassing amount of detail - every three months, his scent would thicken and fill with neediness that was uncommon for the Alpha. Soon after, he would scent the members of his pack, hold them close as they cooed at him and purred in satisfaction, make enough food for the class to live off of for a week, and then he would proceed to lock himself in his room and stay there until his rut finished. Then, he would exit the room in a worse mood than usual and they would all keep their mouths shut as they tried not to look whenever the Alpha readjusted his (probably) aching knot in his sweatpants.

So he didn’t really understand how he managed to forget about it this time - it didn’t even register in his mind that Kacchan’s rut was near until the Alpha missed all of his lessons one day.

Immediately, Izuku realised just why he’d been so restless lately, why he couldn’t stand anyone being near the Alpha, and why he couldn’t help but steal a pair of Kacchan’s boxers after training that he proceeded to shove into his nest while slick dripped from his cunt and his tongue darted out across the fabric.

Maybe that was also why he’d spent the previous night baking for hours - placing cookies and pastries into containers and labelling them all with Katsuki’s name; he needed to take care of him, to make sure he had enough supplies for his rut.

He almost felt silly for missing all the signs, but as soon as he realised what had happened, he waited until night fell and rushed to Kacchan’s room.

And, before he even stepped foot past the threshold, he was hit in the face with faint rut pheromones.

Maybe his stupid Omegan brain was scattered now that he’d presented, affected by the clear reluctance of his Alpha to mate with him, or maybe it was the nervousness he felt thrumming through his body, he didn’t know, but no matter the knowledge that he couldn’t be anywhere near Kacchan - he wasn’t allowed to - he simply couldn’t leave.

All he had to do was turn back around, climb into his nest while the scent of Kacchan’s rut was still fresh in his lungs and make himself cum, and that was it. He would be okay.

But he couldn’t.

Because, despite Katsuki’s lack of interest, Izuku still knew they were fated mates. Just like he knew what Katsuki’s favourite food was, or the weakness he had when it came to anything sweet, or even his favourite hoodie that was worn and torn yet Kacchan could never get rid of it.

He knew him, he knew them and what they were, what they were supposed to become.

This was Kacchan’s first rut since Izuku presented, and something inside of him screamed and yelled with each second that he wasted not being with his Alpha and helping him through it.

Perhaps that was why he was standing in front of his door, fingers pulling at the edge of his T-Shirt and gaze nervously jumping from one side of the hallway to the other as if he knew what he was doing was both wrong and stupid.

So damn stupid.

But Izuku had done plenty of stupid things for Kacchan before, and he wouldn’t stop doing so now, especially when there was no one around to stop him - they were all asleep already, his classmates, the professors, and no one would even think he would do this. No one had to know, including Kacchan.

He couldn’t help it.

His palms were slick when they gripped the doorknob, clad in anxious sweat, and, with shaking movements, he turned it.

An- Oh.

Oh.

It clicked open. The sound echoing in the empty hallway. Loud, far too loud, and Izuku tensed as the seconds ticked by.

Izuku didn’t really expect it to work - he thought that he would try and when the door remained shut, he would simply return to his room as if the attempt had not been made in the first place. After all, Katsuki was known to be diligent in every part of his life, particularly when it came to keeping his den safe - it was important to every Alpha to maintain the sanctity of their den, especially during their ruts, but Kacchan had always been far more intense than most. Even though Izuku had seen many enter the room, he knew Katsuki was still careful, diligent in who he allowed in.

Poor thing must’ve gotten sidetracked in his bleary, rut haze.

Which was exactly why he needed Izuku. He needed his Omega there to take care of him, to make sure everything was perfect and nothing could hurt his Alpha - surely, Kacchan wouldn’t wish for anyone but Izuku to be so close to him in such a vulnerable moment. They’d known each other for years, since they were just pups running around the forest and talking about who they’d become when they grew up - there was no one but him that had the right to see Katsuki during his rut.

Before he pushed the door open, Izuku stopped.

This was his last chance, the last chance to step back and leave and pretend as if he’d never tried to intrude on his mat - his friend in such a horrific manner. Because that was what he was doing - Katsuki didn’t want him there, and there were rules set for all of them to prevent students from spending time together doing their heats or ruts. They weren’t allowed to mate until they all turned 18, after all, and they weren’t trusted to control themselves, stop themselves from biting one another if they chose to spend their cycles by each other’s sides.

His Omega whined, a desperate and needy sound, and it successfully distracted him from the sudden appearance of his distant moral compass.

And so he opened the door, and at the sound of deep breathing, he felt some of the tension fall from his muscles. Kacchan always did have that effect on him - just his mere presence could melt away any worries Izuku had.

When he stepped over the threshold, he did not look, not yet.

Instead, he made sure the door was closed shut, securely locked behind him - it was the only barrier between him, his mate and those who wished to separate them and prevent him from helping his Alpha, as if that wasn’t what he was made for, what his true purpose was.

He wouldn’t allow it, not when Kacchan was hurting.

He would always put Kacchan first. It did not matter who or what stood before him.

When the click of the lock sounded in the room, he turned towards the bed, towards the very centre of Kacchan’s den, where his nest would be if things were right, if they weren’t quite so out of place.

And the doubts of the morality of his actions evaporated into thin air, as if they weren’t even there in the first place.

Because, with Kacchan there in front of him, who cared about what was right and what was wrong? Who cared about the stupid rules implemented by those that didn’t understand how badly he and Kacchan needed each other?

None of it mattered.

Izuku slowly trailed his gaze over the sight before him.

He’d seen Kacchan in various states of nudity before - when they’d gone to the beach as kids, when the Alpha walked around the dorms with only his basketball shorts on, the garment hanging low on his hips as if the Omega’s in the room - fuck, even the Beta’s, the Alpha’s - weren’t staring at him, in the locker room, the showers, but never like this.

All those instances lacked any sort of sexual connotations, but this… this was different.

The sight, alone, was enough to cause his overly-sensitive scent glands to begin swelling up, growing sensitive as oils spread across them, designed to entice his Alpha to bite him, mark him, make him his.

Fuck.

Already, he could feel slick dripping from his hole. Even the feeling of his clothes rubbing against his skin caused him to shiver, goosebumps spreading across his body from how sensitive he had become. Too much. Everything was too damn much yet not enough all at once.

He could hardly keep himself from simply straddling the blond and taking what was rightfully his. What had been his since they were pups.

Because that was what Kacchan was, what he would always be - no matter their tumultuous past or comfortable present, that was his Alpha.

Self-control had never been his strong point, always craving for things that he would reach for regardless of the possibility or lack thereof of success. Always risking things just to get the desired end result. And he very rarely tried to stop himself from doing what he pleased - even with his need to have Kacchan’s scent in his nest, he simply took what belonged to him, what his Alpha should’ve given him in the first place.

But at that moment, he knew nothing would entice him in this way, nothing would ever push his limits this harshly; he was at his breaking point, and the longer he stared, the closer he got to the eventual snap.

Yet he couldn’t seem to look away, he didn’t want to.

Katsuki was sprawled across the messy, tangled sheets, one arm limp beside him while the other was raised above his head, revealing the trail of hair beneath. His right leg bent at the knee, the left hanging off of the bed, foot barely touching the floor. His blanket - one which, Izuku noted, didn’t look anywhere near as soft and warm as the ones in his nest where Kacchan belonged - just barely covered his crotch while the rest of his body lay bare. Yet, Izuku could still see the line of hair trailing from beneath his navel and up to the edge of the blanket, disappearing beneath the stupid covers.

Izuku leaned in, and the light shining from the lamp that Kacchan must’ve forgotten to turn off made sweat glimmer across his golden skin, his nipples pink and pebbled atop soft-looking pecs that Izuku was dying to leave marks on, and, even though the blanket obscured his sight, Izuku could still see his hard cock, his half-swollen knot, and he wanted, he needed it.

It seemed as if the pills, while successful at making him sleep, didn’t quite get rid of all the little intricacies that occurred during ruts. Even with the drugs, that desire, that need to breed and fuck and knot, still thrummed through Kacchan’s veins.

Hm.

Interesting.

Not that it mattered! It didn’t! He only wanted to check up on him, see if he needed any help, any food or something to drink… maybe a warm hole to push his knot into - like any good friend would!

But, apparently, Kacchan didn’t need any help, judging by the mess surrounding his bed - the empty water bottles, some of them uncapped and spilling the remains onto the carpet, wrappers from the protein bars designed for Alpha’s in ruts, tissues strewn across the floor.

God, Izuku just knew Kacchan would be mad at himself when his rut was over - he always did like to make sure every part of his life was organised, that included his room. The few times he’d been allowed to enter his den, Izuku took stock of the way everything had its place - the books, school supplies, figurines, everything.

Maybe he could help him?

Yeah. He could do that!

Good Omega’s always helped their Alpha’s. Good Omega’s made sure their Alpha’s didn’t suffer. Good Omega’s took care of their mate.

And Izuku would be a good Omega, anything for his Kacchan!

On shaking legs, he stepped forward, inhaling deeply in order to calm himseld and, fuck.

Fuck.

His knees buckled, almost making him fall to the floor as a whine escaped from deep inside of him when Katsuki’s full scent finally reached him.

Normally, Kacchan wore scent patches - just like all of them were required to in order to prevent any sort of distractions. But, as much as Izuku appreciated it during training, it meant that Kacchan kept those notes of his scent hidden, and even when Izuku got the privilege of being near him, breathing him in, it was never this strong, this overwhelming - all-encompassing.

He could practically taste it, feel the rut sticking to his skin and his taste buds the closer he got to the bed.

Firewood and gunpowder filled every inch of the room, thick and potent and delicious.

The stale smell of sex hid beneath the layers of frustration and pain.

It was fine, though. It was alright. Izuku would help him, he’d make him feel comfortable, he would rid him of pain.

He was a good Omega. But only for his Alpha. No one else.

With a determined nod, Izuku steeled himself and stood by Katsuki’s side, fingertips itching with the desire to touch, to soothe and get rid of those furrowed brows - he wanted him relaxed.

Instead, he crouched down low and began grabbing the remains of the wrappers, quickly throwing them into the trash can placed near him.

But with every second he spent in his proximity, it became harder and harder to focus - he could hear his deep breaths, the occasional shuffle in his sleep, and the memory of his hard cock was burnt into his mind.

It was fine, though.

He didn’t care. It didn’t matter.

As he moved his hands, the back of his knuckles nudged against something beneath the bed - hard, seemingly made out of plastic. Yet still warm, as if it had only been touched and held recently.

With his bottom lip between his teeth, Izuku hesitated for only a moment before reaching forward and pulling the object out where he could see it, underneath the moonlight shining through the window.

And the second he set his gaze upon it, he dropped it, hands rising to press against his mouth and suppressing his shocked gasp.

Oh.

He knew the Alpha had needs, he wasn’t a complete idiot, and he knew such things were necessary during most ruts, particularly those as violent and harsh as Katsuki’s - the Alpha’s instincts to breed were probably stronger than most, after all.

But he still couldn’t help but falter at the sight of the fleshlight now laying on the floor.

With a quick glance towards Kacchan, making sure he had not suddenly woken up, he held the toy up once more, his breathing coming out shaky and far more nervous than he would’ve liked it to be.

Warm. It was warm.

For a moment, a stupid, absolutely ridiculous and illogical feeling filled his body - jealousy.

He was jealous of a goddamn toy.

But he couldn’t help it! Kacchan didn’t even look at him, he was a willing Omega, desperate to bend over for him and let him use his holes, and, instead of doing that, he opted to use a piece of stupid shitty plastic.

Stupid Alpha.

He knew it was pure instincts driving him to feel this way, as was this strange sort of possessiveness he felt over the Alpha - his Omega was just desperate to please, to own, to be owned in return.

And so he knew Kacchan shouldn’t be using anything other than him, his cunt, his mouth, his ass, anything he wanted.

He just wanted Kacchan. In whatever way possible. Even if it was just getting used during a rut.

A glance towards the toy caused him to hesitate, body tensing as he tried to think.

He didn’t know what compelled him to do so - maybe it was sick curiousity, or maybe it was the knowledge that it was his Kacchan who held the toy, who gripped it with those strong, large hands and pushed his fat cock inside.

With nervous movements, he turned the toy, and only then did he see a drop of cum sliding out of the lubed up slit.

His mind went blank, and he leaned in.

Tongue lolling out, he swiped it across the drop, allowing it to linger atop his taste buds before he swallowed, and a moan escaped it him at the taste. Like a man starved, he moved closer, pushing inside, licking at the insides and tasting the mixture of lube and cum, allowing his groans and moans to fill the silent room.

And when the final drop was gone, he moved away, panting as he looked to the side, right where Kacchan’s head was resting against the pillow.

He dropped the toy to the floor, the thud of it falling barely registering in his mind.

This close, he could see the sweat covering Kacchan’s face, the furrow of his brows and the rapid rise and fall of his toned chest.

A pathetic-sounding whine that he just knew Kacchan would make fun of escaped him and he looked away, only for his gaze to fall upon the bottle of pills placed on the shelf above Katsuki’s bed, right next to the manga he was currently reading.

He shifted closer and read the label.

Oh.

‘Provides 8-10 hours of completely undisturbed sleep.’

Well, he supposed that gave Kacchan plenty of time to rest without having to deal with the pain and the cramps and the insatiable desire for an Omega to knot.

Hm.

When was the last time he had taken one of them?

Surely, it couldn’t have been that long ago, not with how warm the toy still was.

He must’ve taken them right before Izuku came into the room.

Would… Would he wake up with Izuku there?

Would he yell and scream and tell him to get out of his den as if Izuku didn’t belong right there by his side?

Or would he finally realise Izuku was his Omega and he would take what belonged to him, he would grab him and fill him up with that fat cock and bite him an-

Izuku shook his head.

Shit.

Maybe he shouldn’t have come here. Maybe this was a horrible mistake.

But just as the thought appeared in his head, just as he kneeled up and got ready to stand, he glanced down, and inches away from him was the Alpha he’d been fantasising about for far too long - ever since he’d first even figure out just what sex and attraction even were. Before he even presented and learned they could actually mate and be together.

Pink lips parted and scent glands swollen, a picture of perfection.

And, suddenly, a rumbling groan escaped the man, and Izuku stiffened.

It was a sound he’d never heard from the Alpha - deep, frightening, and filled with layers of desire, need, and desperation. And Izuku just knew it was because of him, because his Alpha could sense his Omega was right there.

He could feel his pussy throb at the noise. An ache deep in his stomach, spreading through his entire being. It was consuming. Enveloping him entirely.

Before he knew what he was doing, his gaze trailed lower, over Katsuki’s throat, his chest, the muscles shifting on his stomach, and it finally landed atop the bulge barely contained by the sheets.

Surely, Kacchan wouldn’t mind if he just took a look - after all, they’d seen each other naked before. Izuku still remembers the mocking tone of Katsuki’s voice in the locker room, the way he’d made fun of Izuku’s size. So, it was fine.

This was his one chance, possibly the only chance he’d get to see him before having to wait for Kacchan to finally mate him.

Besides, it wouldn’t matter if he saw it now or… or whenever Kacchan realised he was his fated mate - they were going to end up together no matter what.

With that in mind, he moved his trembling hands and gripped the edge of the covers, dragging them down to Kacchan’s muscular thighs.

And so he watched as his cock sprung out, slapping against his stomach, the tip of it dark red and swollen, dripping with precum which slid down his shaft, veins protruding down the intimidating length and all the way to the half-formed knot.

It was big, far bigger than any of his toys which he had selected specifically because he believed them to be closest to Kacchan’s size, bigger than he thought it would be.

He was certain that if he tried to wrap his fingers around it, he would be unable to do so.

But that would be too far, wouldn’t it?

Looking was one thing, but touching… That he couldn’t do.

No. He couldn’t carry this on, he wouldn’t, it was too much. No matter the temptation, he wouldn’t allow himself to break.

His fingers curled around the edge of the blanket once again, ready to cover Kacchan and his modesty up before he ran out of his den and acted as if this had never happened, as if the taste of Kacchan’s cum wasn’t still lingering on his lips - it was fine, he might struggle with looking the Alpha in the eye without thinking about everything that had happened, but he would be alright.

Just as he gripped the blanket, a whine echoed in the quiet of the room, breaking apart the silence - a desperate, needy noise, akin to a wounded pup, and his Omega chirped in response, attempting to call for his mate and soothe him.

He looked up, green focused on the pain in Kacchan’s expression, drawn on every line of his handsome face, and he already knew he couldn’t leave.

Just this once.

Just this one time he could finally be useful.

A shaky sigh escaped him and he rose from his aching knees, climbing onto the bed with clumsy, yet sure, movements.

The dipping of the mattress did not deter him; after all, Kacchan wouldn’t be waking up any time soon, no matter what he did.

At least Izuku hoped he wouldn’t - he didn’t know how he would explain himself if Kacchan saw him in his den. Perhaps he could pretend he was nothing more than a hallucination.

So he settled between his spread out legs, palms resting against the muscles of his thighs and his lips curling up in a smile at the feeling of Kacchan under his hands, the coarse hairs tickling at his skin as he began to trail upwards, easing the tension out of Katsuki and releasing his sweet scent until Kacchan finally lay lax on the bed, lacking the previous tension he held.

Izuku couldn’t resist, he purred as he smiled down at him, the praise escaping him before he could help himself, “Good Alpha.”

With the words hanging in the tense air, his Alpha’s muscles twitching beneath his touch as if he could hear the praise, as if he knew his Omega was happy with him, Izuku leaned in and pressed his lips against the soft skin of his inner thighs. He hummed as he moved, nipping until red marks bloomed across the pale canvas. He could taste the sweat on top of his skin, the desire the higher up he moved. It was unlike anything he’d tasted before.

He wished he could leave marks, he could bite into the flesh and stake his claim, but he couldn’t. Not yet. Not until Katsuki agreed to do the same to him.

Only when his nose bumped against the crease where his thigh and pelvis met did he stop, and he inhaled, groaning while he did so - here, his scent was stronger, muskier, more concentrated than anywhere else, and hidden beneath the layers of gunpowder and firewood lay pure, unbridled desire.

It wasn’t for him, Izuku knew it was a product of the rut, but for now, he could pretend - he could pretend that while fucking into the toy, Kacchan was thinking of him.

Because who else would Kacchan think of if not him?

Kirishima? No, no. He was an Alpha and… and Izuku knew Kacchan would never look at him in such a way. Their bond was brotherly. Nothing more.

Kaminari? A pretty Omega. Entertaining. Funny. But that was it. Kacchan would not even look at someone of such low class. He wasn’t good enough for him.

The rest of his friends were not ones Katsuki would be interested either - Mina and Sero, far too boisterous and far too foolish in their own right.

Izuku was the only obvious choice.

After all, no one knew him the way Izuku did, no one had grown up with him, no one could please him the way Izuku could.

It only made sense that Kacchan would think about him as much as Izuku thinks about Kacchan.

With the thought deep inside his head, his tongue darted out, and he trailed the length of it over his balls to the tip of his cock, groaning when the taste of sweat and precum filled his senses.

God. He just knew Kacchan would taste delicious.

Of course, he was already aware how sweet he tasted - not that Kacchan had ever found out about this particular discovery; Izuku was many things, but he wasn’t completely and utterly idiotic. Telling Kacchan that he once spent ten minutes licking over his palms and sucking on his fingers while the Alpha was asleep would surely result in his death, as would the fact that he once swiped his tongue across his scent glands. It was forbidden to do so. Only mates could touch those particular spots. Izuku didn’t care. He knew where they would end up, anyway.

But, even then, he didn’t get to taste him like this.

His own pleasure was pushed to the side for the moment, ignored for the sake of flicking his tongue over the slit, over his frenulum until Kacchan growled in frustration, hips bucking upwards and hands clenching around the sheets as if he wanted to rip them to shreds.

Only then did Izuku notice the intricate bracelets around his wrists. Flashing green lights.

Ah.

Quirk-cancelling.

He was probably obligated to wear them, as were some other members of the class - Kaminari, maybe, Tokoyami, perhaps even Todoroki.

It made sense. Quirks were difficult to control alongside instincts and such primal needs.

But Kacchan was so amazing, Izuku was sure he didn’t need them.

For now, he would leave them on, but once they shared their heat and rut together, he wouldn’t let Kacchan restrict himself in such a way. He would let himself get burned, the sparks dancing across his skin like fireworks. Leaving a mark on every spot they touched.

Izuku smiled when he saw Kacchan shift, desperately trying to get the friction back on his sensitive cock.

Finally, Izuku parted his lips and allowed himself to do the thing he’d been thinking of for far too long, ever since he first learned what it even was - he slid down, lower and lower until Katsuki’s cock was hitting the back of his throat and he couldn’t move further without gagging.

His movements were slow, measured, and calculated, just like everything else he did. Every flick of his tongue, every time he wrapped his fingers around Kacchan’s knot and squeezed or trailed his fingertips over his balls, he watched his reactions - whatever made Kacchan’s brows furrow and a low, satisfied groan escape him, he repeated. Whatever made his hips hitch upwards and his fingers pull on the sheets, he imitated over and over again until he could feel his knot begin to grow.

Hand wrapping around the protruding mass, he gripped it tightly, continuing to move his head as the fingers of his other hand trailed over the Alpha’s balls.

His eyes closed shut, he didn’t pay any mind to his surroundings, he didn’t care about anything or anyone outside the room - only the taste and feel of Kacchan on his tongue, only Kacchan’s legs tensing around him, only Kacchan moaning and pushing further into his throat until cum shot down it and Izuku’s eyes widened.

But his shock disappeared the moment he felt Kacchan’s body trembling, back arched and brows furrowed as his lips parted and he moaned in pleasure, writhing on the bed as Izuku groaned and sunk down lower, swallowing over and over again while maintaining pressure on his knot.

He almost wished he could move down, let the knot catch beneath his teeth and make his jaw ache from the strain - if it broke him, it wouldn’t matter, he would take it for Kacchan.

Next time. He would have plenty of chances to practise, to try again and again until he became what Kacchan needed, what he deserved. What he secretly always wanted but did not ask for.

Closing his eyes shut, Izuku hummed and relaxed his head against Katsuki’s thigh, cheek pressed up against warm skin and solid, lax muscles as he suckled at the length in his mouth.

It was almost relaxing, calming in a way he didn’t quite expect it to be.

Maybe, someday, when old bitterness and memories of mistakes weren’t in the way, Kacchan would realise this was what they could have all the time - he didn’t need the toys, the pills, or the pain; all he needed was Izuku.

Hm. Maybe.

Soon, Kacchan’s knot began to deflate and the steady stream of cum stopped at last.

Only, despite the orgasm, the knot was still there, still partly full, and as Izuku moved away, mouth feeling far too empty without the delicious weight on his tongue, Kacchan’s cock began to grow hard once more.

Oh.

No.

It was over and done with - he had already done what he wanted to do, he had helped his future mate and lessened his pain for the moment. That was all he was here to do.

Taking more than what he deserved wasn’t right, not when he had done nothing to earn it - they hadn’t even courted yet, dammit!

And so he ignored the way his underwear stuck to his wet cunt, he ignored his hard little cock tenting the front of his leggings, and he went to stand from the bed.

But the moment his foot touched the floor, Katsuki whined once again - this time, the sound was filled with more pain than before, riddled with agony as his face scrunched up and he began to curl in on himself.

For a split second, Izuku worried he was waking up, but he knew that wasn’t possible - the pills were tried and tested, and they always ensured nothing awoke the Alpha’s taking them.

He couldn’t stop himself, he chirped in response, purring softly and easing himself back onto the mattress, attempting to gain his Alpha’s attention for long enough to distract him from the awful pain he must’ve been in.

Poor baby. Kacchan didn’t deserve this.

His hand settled onto Kacchan’s abdomen, fingertips brushing across his abs before they reached the tuft of hair surrounding his cock, and he wrapped his hand around it once more, stroking up and down and squeezing his knot until those horrible whines finally disappeared.

But the look of discomfort remained in place.

Maybe… maybe there was something else he could do.

They never were a traditional sort of pair, were they?

Courting didn’t matter, they could do all of that after they got through this, when Kacchan wasn’t hurting and begging for his mate to help him.

Yes. That could wait.

It was selfish of him, deep down he knew - disguised under the layers of concern and pretence that he was caring for his future mate lay a selfishness he wasn’t used to feeling.

So used to putting others first, it always made him falter whenever he indulged in these feelings - but since they were just pups, he had been this way with Kacchan. Weak. He was sure had Kacchan known just how whipped he was for him, he would be taking advantage of it any chance he got - after all, Kacchan only had to think about wanting something and Izuku would do anything he could to please him. Kacchan wasn’t like that, though. As smart and perfect as he was, picking up on Izuku’s true feelings - and their mere intensity - had always been something he’d struggled with. His Alpha could be clueless sometimes.

Besides, maybe Katsuki wouldn’t do a damn thing even if he did know. Maybe he would scoff and laugh about how pathetic useless little Deku truly was, and Izuku, in his true lovesick fashion, would soak up the attention he received, even if it was negative.

Yes.

So damn selfish, so greedy.

But, maybe, selfishness was not the only reason he wished to do this.

It would help, it would make Kacchan feel better, the pain would disappear and he would be able to rest without the unsatisfactory orgasms, the screaming of his inner Alpha, or the ache in his body.

Was it really selfish if Izuku wished to help someone else? Even if it meant risking his own safety? Because that’s what he was doing - if someone caught him, he would be expelled, if Kacchan woke up, he would either claim him or he would tear his throat out.

He was risking a lot for Kacchan! The Alpha should be grateful, really.

Izuku glanced at him, at the sweat covering his temples and the furrow of his brows.

Kacchan didn’t deserve to suffer, not anymore. All his life, since his ruts first started, he’d had to go through this horrible cycle in which he felt nothing but pain and frustration.

Not anymore.

Not when he had Izuku there for him.

His hole clenched at the thought, slick dripping from it - useful, he would finally be useful for his Kacchan, his Alpha.

With a deep breath and hands shaking with excitement and trepidation, he pulled his underwear and leggings off all at once, quickly throwing them to the side before he settled between Katsuki’s spread out legs once again.

Like this, with his thick thighs pressed together, rubbing against each other with slick covering the soft skin, and pussy and dick throbbing with arousal, everything seemed far more intimidating than it did before.

Kacchan had always been much bigger than him - taller, now even more so than during their first year, more muscular, shoulders broad and hands able to encompass his entire waist if they wished to do so. And as the years had slowly gone by, he’d only grown more and more intimidating, while Izuku’s height stagnated.

Even for an Omega, Izuku was small, while Katsuki - the leader of his own pack at such a young age - was the prime example of an Alpha.

Tall. Muscles covering every inch of his body. His scent as powerful as his form.

And… And he was right there.

Right there for Izuku to take and do whatever he pleased with.

Normally, Izuku liked the difference between them, he loved the way Kacchan made him feel - small, delicate, safe. His Alpha was able to envelop him whole and hold him close until all he could feel, smell, taste, was Kacchan.

But Izuku had never done anything with anyone else before. No one had ever touched his cunt other than himself - his own fingers and the toys he owned were nothing in comparison to what he would now have to take.

For Kacchan, though, he could do it.

Only for his Alpha.

On shaky knees, he lifted himself up, moving until he straddled Kacchan’s abdomen, hands splayed across his abs, and, gently, he lowered himself onto the shaft of his cock.

The length rubbed against his clit as he began to grind, covering it in his own slick, mixing it with the precum already bubbling at the tip. His movements sped up as the cockhead pushed between his folds, up against his clit and catching on his hole whenever he moved too far.

Just with this, he knew he could cum, he could take and take and take and Kacchan wouldn’t do a thing about it.

Because he was a good Alpha, and didn’t good Alpha’s always give their Omega’s what they desired?

But Izuku didn’t want that, he didn’t want to cum without Kacchan inside of him. It would feel incomplete. An orgasm that was selfish in nature, that had done nothing to help his mate.

He could feel his own slick covering Katsuki’s body, dripping down into his pubes and his balls as his cocklet slapped against his stomach, leaving behind trails of precum upon the skin.

With the ache of his thighs, the muscles trembling from exertion, he slowed his frantic movements, rising in the air and feeling his body twitch from how close he was to the edge.

Only when he felt as if he wouldn’t cum from the lightest touch of his clit did he lower himself onto Katsuki’s thighs.

Distantly, he thought about searching for a condom, even though he knew that Katsuki didn’t have such things in his room. He had no need for them.

After all, who would he sleep with? He and Izuku were meant to be together. And the Alpha surely knew it.

Of course Kacchan would save himself for his future mate.

In the past, he had doubted this - whenever he saw Kaminari, Jirou, Mina, Sero, Tokoyami, the whole damn class or, fuck, even Monoma and Hitoshi, exit Katsuki’s room, he wondered if there was something there. If their messy hair, glassy eyes, and sweat covered skin had anything to do with the knot that belonged to Izuku. Those thoughts never lasted long, though. He would always remember that this was Kacchan, his Kacchan.

And Kacchan would never be unfaithful to him.

So he knew he would find no condoms in the room.

But… But maybe he could go to his room? Ruffle through the drawer where an unopened box lay, waiting for the day Kacchan finally decided to take what was his.

But then, Katsuki whimpered, he let out a pain-filled sound that caused Izuku’s Omega to whine in response. The Alpha’s hips bucked upwards, strong hands gripping the sheets in a tight hold, and the thoughts of leaving disappeared from his head.

It was fine. He was on birth control.

With that in mind, he moved up, kneeling above him and reaching back to hold his cock, nudging it against the opening of his cunt.

And, finally, he began to sink down.

When the tip pushed past his entrance, he couldn’t help but gasp, eyes clenched shut and breath coming out rapidly and uncontrolled - just this was almost too much, spreading him further than anything else before.

Maybe if he had prepared himself beforehand, this would’ve been easier.

But he knew what he was doing - he wanted to feel it, he wanted the burn, the pain, the struggle to take him until he succeeded. He hoped he would feel the ache for the following days, that he would be reminded of his Kacchan every time he moved.

So he steeled himself, opened his eyes, and watched Katsuki as he sank lower.

And lower.

And lower.

Not once did he look away from Katsuki’s face, from his parted lips and elongated fangs. He almost wished he had his phone out, that he was recording his expression as Izuku took him for the very first time - as they both lost their virginities, feeling something other than their own hands and toys.

Next time.

Next time he would be more prepared.

For now, all he could do was pant as he finally sunk down on the barely-inflated knot, pussy walls clenching around the intrusion while he desperately tried to adjust.

And as he felt himself relax, he let out a breathless chuckle.

Fuck, he’d done it.

Finally, he had Kacchan.

With a euphoric look on his face, he leaned back, hand pressed against Katsuki’s muscular thigh, and as he looked down, he saw it - a bulge, a clear protrusion from where Katsuki’s cock was pressed up inside of him.

Shaky fingers trailed across the skin and he whined as he pressed down onto it, eyes closing shut.

Full.

He was so fucking full.

And as his palm pressed down on his stomach, feeling the bulge protruding through the skin, he had a distant thought that this would break him, leave him loose and gaping so that no one but Kacchan would be able to use him, he would be useless for anyone else. Even for himself. He would not be able to please himself, to use his own pussy.

He almost felt giddy at the thought - his Alpha’s perfect Omega. He was made just for him, his cunt ruined and marked by his mate.

Eyes focused on Katsuki, he finally began to move.

It took a few tries for him to gain the rhythm that caused Katsuki’s breathing to hitch, his eyebrows furrowing and shaking hands gripping the sweat-covered sheets beneath them, but once he finally realised what Kacchan liked, he did not stop.

Izuku desperately wished to close his eyes, to focus on the stretch of his cunt and the way it so perfectly hit every goddamn spot inside of him, the slight friction on his clit whenever he bottomed out and the knot pushed his walls apart even further.

But he couldn’t, not when this was the first time he had gotten to see Kacchan like this - this vulnerable, this open with what he was feeling.

Katsuki had revealed parts of himself to Izuku that no one else knew about - he’d cried, he screamed his insecurities, he’d allowed Izuku into a part of his life that was normally kept private, but he had never allowed him, or anyone else, to see him like this.

He was… completely at Izuku’s mercy. Powerless.

His expression was lax, void of any anger or trepidation, and his cock was so big, so fucking hard, all for Izuku to use, to fuck himself onto until tears fell down his cheeks in the way that Kacchan always mocked.

This Kacchan was his - every version of him was, but no one else had had the privilege of seeing him this way.

Izuku rolled his hips, hands placed upon Katsuki’s abdomen, and he watched those pink lips part as a delicate groan escaped him. He could see the sharpness of his fangs, the venom dripping from them and down his chin.

“D-Does that feel good, Kacchan?” Izuku smiled as he spoke, his breath hitching when he began to lift himself up before lowering back down, over and over again.

A soft moan was all he got in response - it was as if Kacchan knew who it was that was speaking to him, who was making him feel so good, who was milking his cock with their cunt.

His Omega.

Izuku’s smile widened and his movements sped up, breathing coming out quick and uneven as he leaned forward and looked at his Alpha, at the sharp lines of his face, the light bump on his neck where his scent gland hid - swollen and sensitive with his rut.

And Izuku knew he shouldn’t even dare to do what he wished to do - it was dangerous, risky, far riskier than what he was doing at that moment.

Yet he couldn’t stop himself even if he tried.

With haste movements, he threw his T-Shirt to the floor and he fell forward, naked chest meeting Katsuki’s as his face fit perfectly into the crook of his neck.

He inhaled, and he clenched down, moaning as his eyes rolled into the back of his head and his lips latched onto the skin before he could even think about what the hell he was doing.

It was Katsuki who snapped him out of the haze he found himself in, Katsuki’s desperate moan, a sound so loud he would’ve feared someone would hear them had the room not been soundproof, followed by a deep, harsh, thrust of his hips.

Izuku moaned, rubbing his cock against Katsuki’s abdomen as he slowly began to move once again, continuing to lick over Kacchan’s scent gland and revelling at the mere desperation in the Alpha’s voice.

So needy, so desperate for his Omega. Almost pathetic.

Izuku smiled at the thought as his eyes watered with tears and lifted himself up on his elbows, inches away from Katsuki’s face.

“S-so good, Kacchan, you taste so good, I love you so much.” He panted, arms trembling as he felt the knot catch at the rim of his cunt.

The lingering notes of gunpowder and firewood were still upon his taste buds, urging him to seek out more, to take and take and take until Kacchan’s neck was bruised up and marked by his Omega and everyone knew not to touch what was his.

A growl fell from his lips as his brows furrowed and he slammed down onto Kacchan’s cock, grinding in circles as Katsuki whimpered and whined.

His expression softened at the sight, and he cood, “Oh, it’s okay, Kacchan - I’m not mad at you, you’re so good. Such a good Alpha.”

He would never be mad at him, not at his Alpha - it was the fact that they were both so stubborn that he detested, the fact that they were yet to fall into each other’s arms the way they were meant to.

It was the fact that he was forced to hold himself back.

Soon. Soon Kacchan would figure it all out and accept him.

He shifted upwards, moving on his cock and beginning to feel his orgasm approaching.

It wouldn’t be long before Kacchan filled him up as Izuku came on his knot - he almost wished he had planned this out a little bit better, that he had stopped using those godforsaken pills and this could result in something, something that would tie them together.

Next time.

He would do better next time.

For now, he simply trailed his gaze over Katsuki’s face, down lower and lower until he reached his chest, until he could see the sweat gathering in the valley between his pecs, the way the muscles jiggled every time Izuku moved.

So pretty.

His Alpha was so strong and so damn pretty everywhere.

His mouth watered as he dared to lean down lower until his lips grazed against a pink, pebbled nipple.

He glanced upwards for a moment, watching Katsuki’s reaction as he wrapped his lips around it and sucked, laving his tongue over the bud and releasing a satisfied purr as the Alpha’s back arched, mouth opening on a gasp as his cock twitched deep inside of him.

Eyes closing shut, Izuku raised his other hand, thumb and forefinger pinching the other nipple as he continued to suck, grazing his teeth against it and moaning as he rode his Alpha.

He could feel his knot growing every time he pinched, pulled, sucked, and fell down onto his cock.

Growing and inflating as Izuku struggled to keep his strength from failing him.

“Good Alpha,” He purred as he raised his head, watching a string of spit break apart from between his lips and the spit-soaked, red, swollen nipple as he continued to toy with the other one - he already knew Kacchan’s chest would be sore, and it settled something primal within him.

At least he would get to leave this mark on him - his nipples red and sensitive from the way Izuku toyed with them. As if he were a common bitch.

“Good puppy, Kacchan.” Izuku moved up as his hands remained on Katsuki’s pecs, squeezing and holding onto them as he pressed a kiss to his cheek, “Such pretty fucking tits, baby.”

With a parting kiss to the corner of his mouth - not his lips, never his lips, not until Katsuki was awake - Izuku shifted until he was sitting up, able to hold onto Katsuki’s chest as he quickened his movements.

The knot was barely pushing past his rim, now, and he knew it would soon be time.

So he moved one of his hands away and reached down to his cock, wrapping two fingers around it and moving them up and down as he moaned and clenched around Katsuki’s cock.

“You’re mine, aren’t you, Kacchan? All mine, my Alpha, and this-” he fell down with a moan as the knot pushed inside his pussy “-is my knot, isn’t it?”

And, finally, the knot caught, growing inside his cunt just as Izuku was pushed over the edge, his cum splattering across his fingers and Katsuki’s stomach, a moan escaping him and his eyes threatening to close shut and the tears spilt down his cheeks in relief.

He watched as Katsuki tensed, and he felt the warmth fill him up, virile cum that he’d craved for so goddamn long as Kacchan’s mouth opened and he moaned desperately, in a loud, primal way that had Izuku consumed with desire.

Katsuki’s hands suddenly gripped Izuku’s waist, hips pushing upwards over and over again as the Alpha rode out his orgasm, and Izuku could hardly hold back a sob at the sight.

His Alpha.

His Alpha wanted him, he was pushing into him, holding him even in the depths of sleep.

Izuku knew this was simply more confirmation they were made for each other - Kacchan didn’t need anyone else, only him.

His hand rested upon his lower belly, feeling the way the skin grew taught as Katsuki fell limp on the bed, still cumming, but finally relaxed, finally without the agony of his rut coursing through his veins.

And as a sob left his lungs, Izuku fell forward, and he pressed a kiss to Kacchan’s scent gland, right where his future bite would be.

“I love you, Alpha,” And he knew, his Alpha loved him too.