Work Text:
Izuku was really starting to hate his new birth control.
It's not that he wasn't grateful for it, he absolutely was. Before he got on this new birth control his heats were absolute murder; they were bad before he got OfA and even worse after, especially with all the broken bones and twisting movement he had to do as a hero student. The cramps were bad enough to have him limping everywhere during pre-heat if not staying home entirely, and no over-the-counter medication seemed to take them away fully.
This new birth control seems to have balanced whatever was messed up and made his cramps more manageable, but it came with an odd - and annoying - side effect. One of those one-in-a-million side effects that your eyes gloss over just because you just never think it's going to happen to you.
Ever since he had started taking his new birth control, Izuku had been lactating.
Not a lot, not enough to be seriously concerned about, but enough to be annoying. Izuku's chest had gained a bit of plush to it since his presentation and now his pecs were always slightly sore, nipples tender enough to need tape so they didn't scratch against his hero costume.
There wasn't even a lot of milk. He had initially ran to Recovery Girl when he first spotted the little dribbles of milk on his chest, thinking for one hysterical second that he was pregnant (even though he had never slept with anyone before), but she had assured him that this was a normal, if uncommon, side effect of certain birth control brands. She also assured him that, as long as his nipples weren't properly stimulated, whether by a pup or a breast pump, the leakage would stay small.
He thought about switching brands again but after thinking about the horrific cramps he had been enduring for years, he decided that a bit of breast milk was a small price to pay to be without crippling pain. He applied for some absorbent padding in his costume and didn't think anymore about it.
It was around his next cycle that he noticed a trend. He thought that the milk just dribbled out whenever it wanted to and, since he was either wearing his costume or his uniform most of the time, he didn't worry about it. The costume absorbed it and his uniform jacket covered his shirt if any wet spots popped up.
But then, about three days before his heat leave, he had realized there was one particular person, one particular alpha that seemed to make him lactate whenever he was in their presence.
Kacchan.
(Of course.)
He didn't dare go to Recovery Girl for this, especially since he already had an idea of why it was happening. Some frantic googling and thorough forum searching confirmed his theory: both omegas who were lactating for pups AND those who had it as a side effect reported that they tended to, uh, produce more when they were around an alpha they had feelings for or were compatible with. The reason dated back to the way, way olden days, when omegas would lactate to attract a mate, to prove they could provide for the alpha's future pups.
So.
Absolutely humiliating.
But Izuku figured it wasn't any worse than when he slicked up when watching Kacchan lift weights or kick ass in training, so he was learning to deal with it. Slowly, embarrassingly, he was dealing with it.
And he thought he was doing a pretty good job too until Kacchan came to his room after an afternoon patrol, scent colored with frustration and misery.
This was a relatively new thing for them. Now that they were repairing their relationship and were friends again, they were doing friend things, like seeking each other out for comfort. They had always found each other's scent comforting, even when they were pups, so sometimes just being in Kacchan's room, and vice versa, was enough to bring him comfort and reprieve.
Kacchan didn't do it as much as Izuku did since he was still struggling with asking for help and things like that, but after particularly difficult shifts he occasionally dragged himself to Izuku's room to flop onto his bed and sit in silence. It was what he did tonight, not even bothering to knock on the door and not saying anything to him either, just flopping face-first into his nest and curling up. He hid a fond smile in his homework and stayed sitting at his desk, knowing that saying anything would scare him off.
He continued working, hoping that his nest, and the slight calming scent he was letting out, would turn Kacchan's scent into something more settled and pleasant, but it seemed like that wasn't working tonight. Kacchan still wasn't saying a word, he knew he wouldn't, since he knew he would see it as conceding and being 'weak', so Izuku finished his work as quickly as he could before tucking it away. He got up and turned his overhead light out, clicking on his LEDs so the brightness wouldn't irritate him. He poked at Kacchan's bulk, making him grumble and half-heartedly snap his teeth before he moved over to make room.
Once he was in the nest and grabbed Kacchan and moved him, ignoring his protests until he was settled with his head over Izuku's heart, body cradled in between Izuku's thick thighs, one of his hands rubbing down the blond's back. Kacchan was tense at first, as he knew he would be, because for all the progress he had made it was still hard for him to accept comfort without getting defensive or angry, but Izuku wore him down. Five minutes pass before Kacchan finally relaxed into him, letting Izuku comfort him. He wouldn't ask what had happened, Kacchan would either tell him or he wouldn't, but right now he needed comfort, and he would always help Kacchan if he needed it.
Everything was fine; he was even able to tamp down on his excitement and disbelief at his crush being on top of him since Kacchan's scent was still pretty miserable. It was going well and he almost thought he would fall asleep.
Until Kacchan started rumbling.
An alpha's rumble, different from an omega's purr, only came out to provide comfort, not express it. Alphas rumbled when their packmates or mates or pups were distressed, and sometimes alphas rumbled to themselves as a way of self-soothing. It was completely normal for Kacchan to rumble right now considering he was still pretty upset from whatever happened on patrol, but the effect it had on Izuku was decidedly not normal.
Objectively, it made sense why he would lactate in response to an alpha's rumble.
Kacchan was seeking comfort, both through his scent and through his actions, and his omega decided that the best way they could comfort their-the alpha was to provide nourishment.
The act of nursing not only nourished pups but also comforted them, getting them close to an omegas content scent and connecting them together.
The difference was, Kacchan was not his pup, and he undoubtedly wasn't interested in whatever comfort his suddenly active breasts could provide.
But of course his omega didn't care to listen to that. His omega just wanted to comfort the alpha they had long since seen as mineminemine and, before he could try to somehow stop it or even manage to push Kacchan away, his shirt was getting wet. Kacchan noticed almost before he did, face scrunching as the fabric under his cheek suddenly grew wet. He pulled away and sniffed instinctively, brow furrowing as he undoubtedly caught the unmistakable scent of milk and not seeming to connect the dots yet.
"It's-!" He squeaked, embarrassed beyond belief as they both watched two wet patches grow on his - tragically bright-colored - t-shirt. "I-it's a side effect of my new birth control, I'm so sorry Kacchan I can't control when or where it happens-"
He cut himself off as Kacchan leaned closer, nostrils flaring as he silently sniffed again. He knew the scent of an omegas milk was potent, laden with all the nutrients a pup would need and slightly flavored with the specific omega's scent, just like their slick was. Kacchan kept leaning closer until his nose was almost brushing against Izuku's nipple through his shirt, now swollen and tender as they always were when he leaked. He was frozen where he lay, not wanting to spook Kacchan and undo all the work he had put in to calm him down.
The room was dead silent around them, quiet enough to where he could hear his own heartbeat in his ears. All he could do was wait and watch his friend, terrified of the moment he would shove himself away and snarl, tell Izuku how disgusting he was. An irrational fear, since Kacchan would never do something like that nowadays, but he couldn't help it as the silence stretched, waiting for Kacchan's judgment to shatter the air around them.
He was almost tempted to say something until Kacchan's mouth dropped open and he -
- he whined.
It was plaintive and needy and probably the most un-alpha sound in the world - not like he cared about that - but it was a beg so strong that he felt his nipples twinge, almost sure that his body was already working to make more milk in response. For a brief second Kacchan looked mortified, but he could see the way his eyes glazed over as the patch on Izuku's chest grew even darker, unconsciously licking his lips at the sight. Izuku felt his omega rear up, slipping instinct-driven thoughts along his own.
Alpha need. Omega provide.
He felt his face flush a horrible red. This was-this was not something his omega should be encouraging! Kacchan wasn't a pup, wasn't his pup, he shouldn't want to-want to nurse from him! It was wrong!
But why? A voice in his head whispered, and he didn't know if it was himself or his omega or a combination of the two. Why is it wrong? He obviously wants it and it'll make him feel better. You want to help Kacchan, don't you?
He bit his lip. He did want to help Kacchan, wanted to comfort him however he could and help that bitter scent go away. And maybe this wasn't the traditional way that most friends comforted each other, but it's not like anyone was getting hurt, right? It might even be a bit of a relief. Before now whenever he lactated he would just have to hold back a wince and subtly rub his chest to ease the ache, but now he had someone who wanted to...relieve him. It might make the soreness go away.
He nodded, mind made up (as if denying Kacchan was ever an option in the first place) and leaned back. An aborted whine slipped from Kacchan's mouth, obviously trying to hold it back but not really being able to but Izuku shushed him, only moving far enough to pull his shirt off. Izuku's tits were small, as was common for male omegas who weren't pregnant, and really only noticeable if he laid on his back so the weight could gather. The subtle swell of them was practically drenched in milk now, after being pressed against the wet fabric of his shirt.
He had barely managed to lay back down before Kacchan was leaning forward and running his tongue along the side of one, clumsily lapping up the milk that had already dripped. He bit back a gasp, not wanting to spook the alpha, but kept himself still and Kacchan continued.
Kacchan avoided his nipple until his little tits were clean from milk, except for two pearly beads waiting at the opening. The alpha looked up at him, pupils blown wide and mouth lolled open but not brave enough to take the final step on his own. Izuku smiled down at him, unbearably fond even with the odd situation, before combing a hand through his hair. A little of the tension in Kacchan's shoulders relaxed and Izuku placed a hand on the back of his head, leading him forward until he latched onto his left nipple.
Izuku hissed a bit at the strong suck when Kacchan latched on, causing him to freeze where he lay, but he quickly soothed him with a hand on the back of his head.
"Easy." He crooned, letting out a soothing scent. "Suck gentle, Kacchan."
Kacchan let out a little noise in the back of his throat, half moan half whine, and followed Izuku's instruction. His next suck was more gentle, only pulling a little at the tenderness of his nipple. It was an easy enough pain to ignore. Izuku didn't know what he was supposed to be feeling, if anything was actually happening, but then on Kacchan's next suckle he could feel it. Feel just a bit of the tension leaving his breast, almost feel the milk coming out to coat the alpha's tongue.
He felt Kacchan shiver on top of him as the taste hit his tongue, suckling again to coax out more of the milk. Izuku himself relaxed with a sigh, grateful for the pressure that was slowly being relieved from his chest. It still hurt a bit, but the relief overshadowed it. He ran a hand down the alpha's back, soothing over his shoulders as he nursed. He could feel that coiled tension that had been weighing his friend down since he came in draining away with every pull of his nipple, every mouthful of milk.
It didn't take long for his own nursing pheromones to hang heavy in the air, sweeping Kacchan's bitter scent away until the entire room was drenched in contentment and relaxation. Kacchan was weighing him down to the bed and keeping him warm in the nest even with his shirt off. There was something so unspeakably intimate about this moment. Kacchan, an alpha who always tried to be the strongest and best at everything, curled up on top of Izuku and nursing from his breast. Taking comfort and letting himself be taken care of for once.
Izuku's omega was more content than he could ever remember being in his life save for maybe when he was a little pup himself, nursing from his own dam. He was in his nest with the alpha he adored, the alpha he was taking care of just as a good omega should. Any pain or discomfort he had felt before drained away with every pull Kacchan took from him. He was practically boneless as the alpha drank his milk, eyes half-lidded and hands lazy as they stroked up and down his back, keeping him relaxed as he nursed.
Most of this was instinct, he knew. He was practically treating Kacchan like he was a pup, like he was his pup, but it didn't make him feel weird like before. Both of them were obviously enjoying themselves and while he might be embarrassed later, right now it was only bliss.
Soon enough though, he felt Kacchan suckle and come up dry. The alpha whined, pulling again, hard enough to have Izuku wincing, before he managed to get a hand on his face to gently pull him off.
He whined as soon as his mouth left Izuku's nipple.
"No," He said, almost petulantly, "More!" Izuku just shushed him, words coming up on instinct.
"Shh, it's alright, pup. I have more for you on this side." He cooed, leading Kacchan over to his other breast. The alpha's eyes fluttered, lapping at the milk that had beaded when he was focused on the other nipple. He licked it all up and pulled back once it was clean, confusing Izuku since he thought he would go straight in for more. He looked up at the omega, pupils wide and face flushed.
"Thank you, mommy."
And before he could even begin to process that Kacchan had leaned back in, taking his right nipple into his mouth and nursing again. He felt like his face almost went up in flames when Kacchan said that, so open and sweet.
It was so incredibly adorable, and touching, and a little humbling that the alpha trusted him this much.
It definitely shouldn't be making him slick up.
To be fair he didn't even KNOW that was something he was into until the moment that Kacchan said it, He knew people had kinks like that, had heard his friends both make jokes and have half-serious conversations about it. He just didn't think he was one of those people. So he couldn't really be blamed for the way his panties got wet when Kacchan called him that. His pheromones were already all over the place from nursing the alpha and this only made things more confusing. He was still content and blissed out but now he was also aroused.
With each moment that passed with Kacchan latched on and his hard, broad body weighing him down, Izuku's body craved more for a knot. His knot specifically, not that he would ever ask. Besides, this wasn't about him. This was about Kacchan. Kacchan was the one who needed comfort, and closeness, and nourishment. Whatever stupid reactions his own body was having weren't important. He wanted to help the alpha first and foremost.
So he did his best to ignore his steadily mounting arousal, not even shifting as his panties got so wet his slick started leaking onto his thighs. He didn't make a single noise of complaint as he grew even more desperate, wanting to be filled. At this point, he thinks he could go without a knot as long as he got filled with something, anything.
He was thankful that Kacchan seemed so focused on his meal, hoping it would keep him distracted enough to not notice the arousal spicing the air.
It was a fool's hope.
He could only watch as the alpha's brows furrowed, eyes cracking open from where they had slid shut in bliss as he nursed. His nose crinkled as he sniffed, not taking his mouth off of Izuku's breast for even a second.
He snuffled once, twice, before it seemed to click behind his eyes what he was smelling. He opened his mouth to offer an explanation, or maybe an apology, but before he could even say anything the alpha was moving.
He shuffled up onto his knees, carefully leaning forward so he didn't detach from the omega's nipple as he put space between their bodies. He didn't even have the chance to ask what he was doing before his pants and his panties were both gently, but surely, pulled down his legs. In what felt like a moment he was naked, still technically hidden from the both of them by the way Kacchan was still latched on, but his thighs trembled as cool air hit the slick between them all the same. Kacchan's hands moved to his own waistband, shoving it down until his dick flopped out. Izuku squeaked when he felt it fall onto his thigh, hot and thick and so, so hard. He mourned the fact that he couldn't see it. Kacchan gripped both of his thighs and hitched them over his waist, pushing and pulling and confusing him.
It didn't click in his mind what the alpha was doing until he felt the head of Kacchan's cock pressing against his opening, rubbing against the slick there, before slowly, smoothly, pressing inside. He was so wet and relaxed that it took barely any effort to take him to the hilt. He couldn't hold back his moan even if he wanted to. The sudden full feeling had him reeling, eyes rolling back and squirming beneath the firm body of the alpha. Kacchan grumbled around his tit before settling back down, seemingly having no plans of moving or fucking.
He blanketed himself over Izuku again, contentedly suckling at his nipple just like had been, as if he hadn't just speared Izuku with his cock. He clenched around the cock inside him on instinct but, besides a little twitch of his hips, it seemed like Kacchan didn't even notice. He waited another few moments to see if anything would happen, but it seemed like Kacchan was perfectly happy to continue nursing with his cock snug inside Izuku's pussy. He scented a bit of arousal in the air but it wasn't pressing or frantic, like he was holding himself back.
He blamed it on the heavy pheromones that were still laden in the air for taking so long to put it together. Kacchan had obviously scented his arousal and responded by filling him up, exactly like he wanted, without him even having to ask. He was taking care of Izuku, just like Izuku was taking care of him.
The thought brought happy tears to his eyes and he relaxed back, lazily squeezing around Kacchan's cock as the alpha continued to nurse, feeling safe and full in his nest.
Kacchan eventually dozed off while suckling, head propped against the side of the nest with a nipple still in his mouth, and his cock still in his hole. He was thankful that both of them managed to get ready for bed before all of this happened because he couldn't imagine moving.
He knew Kacchan had stayed latched on through the night because he woke up in the same position, slightly sore but more satisfied than anything else. The alpha was still asleep, and he watched fondly as he suckled every so often, more out of comfort rather than seeking milk.
It became something of a routine for them; whenever Kacchan was stressed or down or upset he came to Izuku and nursed from him, letting the omega croon and stroke his hair as he languished in his calming scent and tasty meal. Sometimes he just nursed, sometimes he nursed while Izuku cockwarmed him. The omega didn't get aroused every time it happened, but with Kacchan's penchant for calling him 'mommy' whenever he was particularly content, he did slick up every now and then. Kacchan was all too happy to offer his cock to satisfy the omega just as his milk was satisfying the alpha. Everyone was satiated in the end.
Their little habit followed them as they graduated, through the years they sidekicked and lived together, to their marriage and the birth of their first pup. Though he did have to deal with a pouty and needy alpha whenever he nursed their little Katsumi. Eventually Izuku got used to nursing them both at the same time, basking in the comfort of his little family and so, so grateful he had switched his birth control all those years ago.