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Katsuki scowled as he trailed behind his mother, hands stuffed into the pockets of his hoodie. They were at a park—of all places. A park. At fifteen, Katsuki was sure he was too old for this kind of thing. Mitsuki Bakugo wasn’t the sentimental type either, so her dragging him here without much explanation felt off.
“Why are we even here, old hag?” he muttered, kicking a stray pebble on the path.
Mitsuki shot him a sharp look but didn’t answer. Instead, she motioned toward a nearby bench. “Go blow off some steam. I need to make a call.”
“Tch,” Katsuki grumbled but wandered off anyway. He didn’t really want to pick a fight right now—not with her, at least.
As he ambled through the park, the sound of children’s laughter and the rustling of leaves filled the air. It was annoyingly peaceful. He was about to plop himself down on an empty bench when something caught his eye.
By the sandbox, crouched in the dirt, was a green-haired boy. The kid was small, maybe younger than him by a year or so, with freckles scattered across his cheeks and a focused expression as he carefully packed sand into a bucket. The boy’s hair was messy, catching the sunlight in shades of emerald, and there was an odd calmness about him that Katsuki couldn’t look away from.
He didn’t realize he was staring until the boy suddenly glanced up, meeting his gaze.
“Oh!” the boy said, startled at first. Then, he smiled—a warm, inviting smile that Katsuki didn’t know how to respond to.
“Do you wanna join me?” the boy asked, holding up the bucket.
Katsuki blinked, caught off guard. His first instinct was to scoff and walk away. He wasn’t here to play with some random kid. But for some reason—maybe it was the way the boy was looking at him, hopeful and genuine—he found himself shrugging.
“Whatever,” he muttered, stepping into the sandbox.
The boy’s smile brightened. “Great! I’m Izuku, by the way!”
Katsuki didn’t reply right away, instead plopping down across from him and grabbing a handful of sand. He felt weirdly self-conscious but tried not to show it. “Katsuki,” he finally said, his voice gruff.
Together, they worked on the sandcastle, with Izuku chatting excitedly about techniques to make it stand taller and stronger. Katsuki mostly grunted in response, but he secretly enjoyed the attention. It was rare for someone to notice him without flinching or bracing for his sharp tongue.
Just as they finished adding a moat, a warm voice called out from the distance. “Izuku!”
The green-haired boy perked up, brushing sand off his hands. “That’s my mom! I gotta go.” He looked back at Katsuki with a wide grin. “Thanks for helping! Bye, Katsuki!”
“Yeah, whatever,” Katsuki said, his tone indifferent. But deep inside, he felt a strange warmth at being acknowledged.
As Izuku ran off toward the voice, Katsuki stood up and followed the path back to where his own mom was waiting. He spotted her sitting on a bench—next to a woman with soft features and curly green hair. The green-haired boy from the sandbox was now clinging to her side.
Mitsuki waved him over. “Katsuki, come here.”
With a sinking feeling, Katsuki obeyed, his sharp mind piecing things together. His mom never brought him to parks, never casually met with strangers. This wasn’t random.
“Katsuki,” Mitsuki began, gesturing to the pair, “this is Inko and her son, Izuku.”
Izuku smiled up at him, his face lighting up with recognition. “Katsuki!”
Katsuki shoved his hands back in his pockets, trying to mask his surprise. “Tch. Yeah, I know. We already met.”
Inko laughed softly, her voice as warm as her son’s. “What a coincidence! It’s nice you two got along.”
But Katsuki knew better. His mom might’ve thought she was being subtle, but he could see the glint of intention in her eyes. This wasn’t just some casual introduction.
It meant something.
“Don’t tell me you’re trying to—” Katsuki started, but Mitsuki cut him off with a sharp glare.
“Not now, brat.”
Katsuki clenched his jaw but said nothing. He wasn’t stupid. His mom was trying to blend their lives together, bit by bit. It didn’t matter if there wasn’t a ring yet. This was her way of saying get used to them.
And as much as he hated change, Katsuki couldn’t help glancing at Izuku again. The kid was still smiling at him, the same bright, hopeful grin from earlier.
Maybe this wouldn’t be so bad after all.
----
Katsuki wasn’t stupid.
After his omega dad passed away, his mom had thrown herself into work, her fiery personality burning through the grief. But something changed recently. Her sharp edges softened; her usual scowl replaced by rare, fleeting smiles. It wasn’t just her demeanor—her scent shifted, too. The tangy, fierce undertone of a driven alpha had mellowed into something warmer; more content.
Then there were the dinners. Mitsuki never cared for eating out, preferring quick meals at home, but now there were frequent evenings where she’d come back with the faintest hint of lavender and chamomile clinging to her. Katsuki could smell it—a signature Omega scent—and he wasn’t surprised when she finally dragged him to meet Inko and her son, Izuku.
From then on, visits became routine. Inko started dropping by their home, her calm presence filling the space with an unfamiliar warmth. Sometimes, Katsuki and his mom would head to the Midoriyas’ house instead. Over time, Katsuki got used to Izuku, who was shy but cheerful, always trying to strike up conversations. They weren’t close, but they were familiar.
Then one day, Katsuki noticed something different. Izuku had started wearing a collar—a soft, green band snug around his neck, unmistakably marking him as an omega. Katsuki’s crimson eyes lingered on it for a second longer than he’d care to admit before he looked away with a scowl.
The day came when Mitsuki and Inko gathered them both in the living room.
“We’ve decided to get married,” Mitsuki announced, her voice firm yet calm.
Inko smiled, her hands clasped tightly in her lap. “We’ll be one family now. Isn’t that wonderful?”
Izuku beamed, his green eyes lighting up with excitement. “Kacchan! We’re going to be brothers!”
Katsuki barely held back a snort at the nickname, rolling his eyes. “The hell is Kacchan? Tch. Whatever, Deku.” The nickname slipped out almost instinctively, his way of masking the strange, twisting feeling in his chest.
Mitsuki reprimanded him for it, yet Izuku paid no mind. Thus, the nicknames stayed.
The months passed quickly, and before Katsuki knew it, the wedding day arrived. It was a simple ceremony, but the way Mitsuki and Inko looked at each other made it feel significant.
Now, living under one roof, Katsuki was faced with the reality of his new family. Inko’s cooking filled the kitchen with tantalizing aromas, and Izuku’s constant chatter buzzed in the background of his days. It was strange, having someone call him “Kacchan” so earnestly, so warmly.
And yet, every time Izuku smiled at him, his collar glinting faintly in the light, Katsuki couldn’t quite shake the feeling that life had taken a turn he hadn’t seen coming.
----
Mitsuki and Inko went to a business trip leaving the young alpha and omega alone.
Izuku had been tidying up the house, dusting the furniture and rearranging things when he started feeling overheated. The warm spring air had seeped into the house, and he decided to take a quick shower to cool off.
Meanwhile, Katsuki had been out playing basketball with his friends. He returned home drenched in sweat, tossing his shirt into the hamper and heading straight for the bathroom.
He pushed open the door, not thinking anyone was around, only to freeze midway in the doorway when he saw Izuku standing under the spray of the shower. The sight of his stepbrother—his toned, wet body covered in soap—took him completely by surprise. His gaze involuntarily lingered over Izuku, caught in the unexpected moment. Katsuki's eyes roamed around the naked omega's body from his cute plump breast to his curvy hips, down to his trimmed green pubes, in which he is sure a slicking cunt is hidden, then to his round ass and thick legs.
Izuku, oblivious to Katsuki's presence at first, continued rinsing off, his mind focused elsewhere. It wasn’t until he turned slightly, catching sight of Katsuki standing in the doorway, that the shock hit him. He quickly grabbed for a towel, his face turning bright red as he stammered in embarrassment.
Katsuki, equally startled, immediately averted his gaze. “Sorry.” he muttered, retreating quickly, his face flushed with embarrassment.
Izuku, still flustered, sighed and muttered to himself, his heart still racing from the unexpected encounter.
Katsuki slammed his door and immediately held his bulging cock. The image of Izuku’s naked body was still plastered in his mind. “Fuck! Fuck! Deku.”
His hand stroked his massive length as he pictured himself in between of those thick legs straddling his face as he ate that pussy out. He recalled the lingering jasmine and green grapes that he can taste it on his mouth.
“Deku…fuck, I gotta have that cunt.” His hands moved faster, and his grip tightened while chanting “Deku” repeatedly. His cock vibrated as he climaxed picturing Deku fat cunt on his face.
Katsuki looked at his cum-soaked palm and chuckled darkly, “Haa. Fucking shit.”
----
Ever since the incident, which was never brought up. The sudden tension filled both Izuku and Katsuki. The blond alpha will take every opportunity to put his hands all over the greenette omega.
From elbows touching during meals, to shoulders bumping when they do the dishes together. Or to subtly touching Izuku’s neck as Katsuki passed by the living room.
Izuku found it unsettling at first, but the touches were gradually reeling him in that he felt himself touch starved. He would move closer to the alpha waiting for warm hands on his skin.
One night, Izuku was busy cooking dinner, since their moms were out for a dinner date. He was left alone again with his stepbrother. Izuku plugged in his earbuds and played his favorite band. He was cooking a simple miso soup and sauteed vegetables when he felt a looming presence at his back.
His instincts were all up yet before he can turn around, arms wrap around his waist. Izuku sucked his breath in as he was assaulted by a fiery peppermint and dark chocolate.
“Kacchan…” He exhaled.
“Mmm…Deku, it smells good. What’ya cooking?” Izuku knows that his stepbrother is not pertaining to his dish as he can feel the alpha sniffing his collared neck.
“I-I’m cooking miso soup and some vegetables. C-can you help me set the table?”
“Mmm…” Katsuki hummed and moved away from the trembling omega. Izuku sighed in relief, but his cheeks burned bright at thought that one day Katsuki might eat him up.
----
Izuku had been thinking about how to mend the awkwardness between him and Katsuki. The tension that had been building up was starting to weigh on him, and he knew that the best way to address it was with time, patience, and maybe a little bit of effort. So, he came up with a plan.
He invited Katsuki to his room, wanting to keep things casual, and suggested they watch a movie together. It wasn’t anything fancy—just a simple setup with a blanket on the floor and an action-packed sci-fi movie playing on his laptop. He thought it would be a nice, neutral way to spend time together without the pressure of words or expectations.
They sat there, the room dimly lit by the screen’s glow, both lost in the movie. The sounds of the action sequences filled the space between them, but the quiet was far from comfortable. There was an unspoken tension that neither of them could ignore. Despite the effort to relax, Izuku couldn’t shake the feeling that something was still off.
Then, in a quiet moment, he felt it. Katsuki’s hand, surprisingly warm, rested lightly on his thigh. His heart thudded in his chest; the air suddenly thick with something he couldn’t quite place.
Izuku’s thoughts raced, but he didn’t pull away. Instead, he remained still, feeling the heat of Katsuki’s hand pressing through his skin like hot branding.
“K-Kacchan…your hand, they uhm…” Izuku stammered as he felt the hand moving upward until it reached the hem of his shorts.
“Shh…be quiet. I can’t hear the movie.” Katsuki replied but sly grin can be heard from his voice.
Katsuki’s hands continued moving up until he can feel the underwear of the omega. He grinned as he heard Deku whimpering but made no effort to stop him. This stoked his ego to continue his ministrations.
“Spread your thighs, Deku.” Katsuki whispered lowly yet his eyes were still on the screen. He heard some shuffles and felt Izuku’s legs slowly moving sideways. This granted him access to feel the mound of the omega. His thumb swiped along the omega’s clitoris and Izuku shuddered beside him.
“K-Kacchan…what are you doing?” Izuku whimpered and rested his head on the alpha’s shoulder.
“Nothing. I’m watching a movie. We’re watching a movie as you suggested, Deku.”
“But your hand…you keep touching my…” Izuku moaned voicelessly as Katsuki did another swipe of his thumb.
“What am I doing, hmm Deku?” Katsuki was smiling victoriously as he finally looked at the omega wantonly trembling by his side.
Izuku looked up and his eyes met burning crimsons. The omega’s eyes glazed with want and desire that he bit his lips lightly, “Whatever you’re doing, don’t stop.”
Katsuki chuckled, “Good boy, Deku. Such a dirty whore, aren’t you? Now strip, or else I’ll stop all of this and go back to my room.”
Izuku moved slowly and remove his shirt first, Katsuki revel on sight as the perky buds and a slight plump of breast met him. “Hmm…sexy. Strip for me, nerd. Show me your fat cunt.”
Izuku nodded and with shaking hands and trembling legs, Izuku stripped down his sleep shorts and was about to remove his panties, but Katsuki halted him.
“Hmm on second thought, not yet. Come here, Deku. Stand in front of me. In front of my face.”
Like a little lamb, Izuku gulped and followed the alpha. He stood in front of Katsuki. The blond alpha was still on the floor, so he kneeled and leveled his face with Izuku’s clothed cunt.
Katsuki buried his face over the cloth and sniffed Izuku’s potent smell. Izuku moaned on contact and held his mouth to refrain making more sound as their moms were probably still awake.
“You smell fucking good, Izuku. So good. Fucking mine to smell.”
Katsuki continued burying his face over the omega’s mound and Izuku instinctively put his hands on Katsuki’s head to push him closer. Katsuki’s wet tongue licked over the fabric and Izuku held his whimper; his fisting of Katsuki’s blond locks tightened.
“Haa…mine. Fuck, you’re a fucking dessert, Deku. So sweet, so fucking sweet.” Katsuki continued lapping over the fabric as Izuku’s slick poured out.
Izuku was lost in the clouds as he felt himself close to cumming, yet Katsuki stopped his torturous tongue. He stood up, removed his clothes except his boxers and laid on Izuku’s bed. Izuku’s eyes widened as he saw the massive bulging on his stepbrother’s boxers. He instantly drooled over it thinking how big Katsuki really is. Will it fit?
“Remove your panty, Deku and come here.” Katsuki ordered and Izuku followed religiously and removed his now-wet panty.
Naked, Izuku crawled on the bed not knowing where to position himself. “Not there, nerd. Come here, sit on my face.”
Izuku’s mouth dropped as he heard the demand of the alpha. Yet, he breathed a lot of air and courage in and straddled the alpha.
“Move up, Deku. I want your cunt in my mouth.”
Izuku positioned himself properly and put his hands on the headboard. He carefully carried his weight and sat down on Katsuki’s face.
Hot tongue touched his clit that made him quiver in an instant that he forgone his weight and fully sat. “Fuck!” Katsuki cursed, yet his hands cupped Izuku’s peachy ass spreading them.
Katsuki’s started eating him. Wet tongue moved up and down his clitoris that Izuku arched his back on every contact. His slick was pouring like a river and Katsuki slurped them like a warm bowl of miso.
Katsuki’s tongue moved away from his sensitive clit and went down to the omega’s gushing hole. His tongue poked inside and fucked his cunt. Izuku was trembling, moaning and a complete mess as Katsuki ate him out noisily.
“K-Kacchan…I’m close…please…” Izuku didn’t know what he was pleading for, and he didn’t even notice he was moving in sync with the alpha’s tongue. Izuku moved his hips languidly as pleasure started building up, then he moved a little faster, then faster until he was panting hard yet rubbed continuously his mound on Katsuki’s mouth. The alpha nipped and sucked his clitoris that Izuku was sure that it’s already swollen.
With one last flick of a tongue, Izuku shattered and cum strongly on Katsuki’s mouth. Katsuki ate him cleanly, with no slick and cum wasted.
Izuku lifted himself up and laid beside his stepbrother. Silence filled the room that it lulled Izuku to sleep. Just before his senses numbed, he heard Katsuki, “I’ll fuck you, next time.”
Then Izuku blacked out. Movie still playing on background.
----
“Katsuki, don’t you bully sweet Izuku, okay? We’ll be gone only for a week. I will be putting credits on your cards so don’t stay holed at home. Go out with your friends but be safe, okay?” Mitsuki crossed her arms as she waited for her wife to come down and be on their way.
“Tch. Yeah, yeah. I never bullied, Deku. I’m the fucking best brother he’ll ever had.” Katsuki rolled his eyes and smirked on Izuku and raised his eyebrows.
Izuku flinch on the implication yet remained composed. “Don’t worry, Mama. Kacchan takes good care of me. Please have a safe trip.”
Inko came down with her luggage, “Izuku, don’t be a burden to Katsuki, okay? Also help each other with the chores. I’ll miss you, both.” Inko hugged Izuku and petted Katsuki’s head.
The couple set off, and by the time the gates were fully closed, Katsuki grabbed Izuku and pinned him on the sofa. “Hmm…what should we do for a week, Deku?”
Izuku’s heart raced but his eyes never leaving the smirking alpha. “Whatever you want, Kacchan.”
Katsuki grinned deviously and took Izuku’s mouth. The kiss was bruising, hot and wet. Katsuki curled his tongue with Izuku’s, slurping the omega. Saliva drooled over them, yet the brothers paid no mind and continued swapping spit.
Katsuki broke the kiss and hurriedly removed Izuku’s shirt. He cupped the plump breast of the omega and dived in to bite his nipple. Izuku moaned yet offered more of himself as the pleasure started clouding his mind.
Katsuki then moved to other bud and gave the same special treatment as the other received, Katsuki’s hands roamed down and cupped Izuku’s wet cunt. “Already wet, nerd? I knew you’re desperately waiting for our moms to go. Can’t wait to have your brother pound you hard, hmm?”
Izuku moaned in response and spread his legs wider to cater Katsuki’s body pressed on him. “Kacchan…more…” Izuku drunk on the alpha’s pheromones, rubbed himself on the bulging cock of the blond.
Katsuki removed his clothes and Izuku’s remaining clothing article. His dick sprang free, and he rubbed it on the omega’s-soaked cunt. Katsuki grabbed the omega’s hips and lifted it to his face. Izuku’s glistening pussy on plain sight and Katsuki dived in. Tongue tasting the sweetness of jasmine and green grapes making him lose his mind.
After sucking Izuku dry, Katsuki positioned himself and his blunt tip seeking entrance to Izuku’s tight walls. “Kacchan---slowly…you’re so big. It hurts.”
“Shh…hold on to me, you already took me twice, it won’t hurt thrice.”
Katsuki pushed more until Izuku’s walls caved in and welcome the massive and curvy length of the alpha. “There…see you can fucking take me, Deku. I know your cunt was made for me.” Izuku nodded yet tears framed his face but urged Katsuki to start moving.
Katsuki started moving and speared Izuku. He held the legs of Izuku up and moved in and out rhythmically. Izuku’s loud moans filled the empty house as Katsuki’s grunts and groans on the background.
Katsuki flipped the omega on fours and pounded him hard. Izuku held on the armchair as Katsuki bred him good. Every thrust of the alpha, Izuku can feel its fullness. He feels how hot it is, how consuming and how good it is. “Kacchan…feels good. So good.”
“Haa…fuck, you’re fucking tight, Deku. You want my knot, nerd? I’ll fucking knot you.”
“Yes Kacchan…mmm I want it so bad.” Izuku raised his hips more as Katsuki hits his pleasure spots. “There…oh gods. Kacchan!”
Katsuki hovered over him and grabbed his head sideways for a punishing kiss. They kissed wetly as Katsuki rammed him deeper and faster. Katsuki traced his clit and rubbed it while abusing his hole. “Nggghhh…Kaccchan I’m coming, I’m coming!”
“Cum for me, nerd. Let it all out.” Katsuki sucked on his neck and bit on his collar. Katsuki’s knot started to swell, bulging on Izuku’s womb. It locked and loaded Izuku’s breeding hole full.
Izuku slumped on the sofa with Katsuki on top. Both panting hard, still in post-coital bliss but they know it’s just the start of their week free of adults.
----
It became a routine, every time the adults went out, the young alpha and omega would find themselves knotted in every part of the house. They tried to be on their best behavior whenever Mitsuki and Inko are around. Yet, the lingering gazes and touches remained heated and unseen.
Years passed by and Izuku and Katsuki are now entering university. The brothers requested to have their own place near their university in which their moms approved believing the harmonious relationship of their sons.
Time went by again and both graduated colleges. Katsuki and Izuku went home and Mitsuki spotted a mating mark on the omega’s neck and smells suspiciously like peppermint and dark chocolate. Mitsuki eyed Katsuki and the grown alpha just gave a knowing smirk at his mom.
The next time the brothers came home, Izuku was pregnant. Inko was worried since his omega son did not disclose who was the alpha who knocked him up. Saying it was a mistake, but they don’t have to worry since Kacchan is taking care of him. Mitsuki looked at his alpha son who is bearing a smug grin. Mitsuki clenched her fist but said nothing.
“Nana!” The five-year-old daughter of Izuku ran to greet Inko. Inko lifted her up and nuzzled her. “You’re such a sweet child, Ringo. Just like your mom.”
“Ringo? Is that you darling?” Mitsuki called from the kitchen. She heard footsteps running towards her. She was greeted by a curly blonde little girl with red doe eyes and a speck of freckles on her face. Such a copy.
“Grandma! It’s Ringo!” A bubbly laugh filled the kitchen that whatever Mitsuki was thinking, it disappeared momentarily.
Izuku and Katsuki arrived with a basket of fruit. Ringo was already helping setting the table with Inko and Mitsuki gave a single look to his alpha son whose hand were obviously wrapped around Izuku’s waist.
“Katsuki.” She called and signaled him to follow her.
Katsuki whispered something on Izuku’s ears and went to his mom. “’Sup?”
“I’ve held it for years, brat. For fucking Inko’s sake. But what the fuck were you doing? Izuku’s your brother.”
“On paper. Not by blood. Ringo’s your blood.” Katsuki replied curtly. Shrugging his shoulders.
Mitsuki breathed in deeply, controlling her temper. “Katsuki, you better fucking know what you’re doing. Goddamnit, I swear if Inko gets hurt with this---”
“Tch. I fucking know, old hag. Just live your life to the fullest. You had your fun with mama Inko, and I’m building a life with Izuku. Some fruit is not far from its tree.”
Katsuki strode away slowly from his mom, yet before truly leaving, he dropped, “Besides, we’ll move abroad so Deku can give birth to our second pup. We’ll send postcards.”
End.