MS!BKDK ABO AU

When omegas first present, it works kind of like when a duckling is born. At age five, Izuku presented while standing next to Katsuki as they both picked out a pack of hero trading cars.

His eyes latched onto Katsuki and he imprinted on him.

It didn't work the same for alphas, though. Alphas didn't imprint. They only bonded. Still, Katsuki was subjected to the symptoms of Izuku's imprinting.

The younger omega would always follow him around, wheezing with exhaustion as Katsuki tried to outrun and lose him.

On days when he couldn't find Katsuki or Katsuki was off playing with his friends, he'd come home to find tiny Deku crying in front of his house, whimpering, "Kacchan.." It only stopped when he saw Katsuki.

Not that Katsuki paid him any mind. He just walked into his house.

It continued as they got older, but it gradually changed. Soon it was Deku taking his things. Not very noticeable ones - maybe an eraser, a pencil. A used tissue. Anything the alpha had touched.

Ten-year-old Katsuki would growl at the smaller boy. "What's wrong with you?"

"I-I don't know," Izuku would stammer. But he would go home and every night sleep with one of the things he'd pilfered, Katsuki's faint scent enveloping him in a blanket of calm.

It was around that time he started getting those heat symptoms.

Deku would get super anxious then, finding Katsuki immediately after school and crowding him, latching onto him with those sobs, "Don't leave, Kacchan."

Katsuki was so baffled by it he sort of just let it happen, though not without reprimand.

"Shitty Deku. So pathetic.

How're you gonna survive when I'm a big hero and you're a wimpy loser?"

Deku would just sniffle at that, clutching tighter to the other boy as if he could keep him with him if he tried hard enough.

Within the next year or two, Katsuki started experiencing more alpha symptoms.

He didn't feel as bothered by Deku trying to cling to him, not that he would tell the small omega that. He'd let Deku come home with him most days. Katsuki wouldn't really talk to him, but he'd let Deku silently do what he wanted for the most part.

It felt kind of nice to lie in bed with Deku curled around him, head on his chest as they leisurely watched a rerun of one of All Might's fights. "Such a baby," Katsuki would mock as Deku nuzzled himself against his collarbone, trying to hide his own pleasure.

He knew this was when Deku was most comfortable. Whenever they were apart, the omega was abuzz with anxiety, an intense need to be with the alpha he imprinted on overtaking his senses.

Part of him liked that. Deku needed him and only him. And he'd do anything Katsuki asked.

That's how he would find himself working on homework, with Deku underneath the desk between his legs. It was Katsuki's idea at first.

"I just need to be close to you," Deku said one day as they laid in Katsuki's bed.

Katsuki tutted, looking away. But his wheels were turning.

"You wanna be closer, huh?" Katsuki asked, hand moving to his zipper. "Fucking prove it."

So Deku did. It didn't feel as good as Katsuki's hand at first. Katsuki would have to take control, gripping Deku's hair hard and fucking his face until he was a slobbery, sobbing mess.

Still, he could tell Deku loved it by how blown his pupils got, how eagerly he licked and sucked, and his pleased moans as Katsuki used him. He'd happily chirp when Katsuki came in his mouth, slurping it up and swallowing.

It became pretty routine.

Deku would suck him off just about every night while he worked on his homework. Then Katsuki would fuck his face again later. Sometimes he'd have him lay on the bed, head hanging off like he saw in porn. It felt amazing to watch Deku's throat stretch from his generous cock.

Sometimes he'd have him do it while he watched TV, one hand idly playing with the omega's hair as he suckled on him, slow and leisurely, often for up to an hour. He'd gotten a lot of experience, learned how to work Katsuki to the brink only to let him cool back down.

Over and over again, until Katsuki was bracing himself against Deku's head, plunging in as deep as he could and growling his climax. "Fuck! Yeah, that's right. Take it, Deku. Mmm, fucking swallow it all. Shit!"

After that, he'd tuck his cock back in his sweats and lie boneless.

He would vaguely register the wet spot on the front and back of Deku's pants, evidence of how just getting Katsuki off got the omega off. He couldn't help but feel powerful at that.

Whenever Deku was anxious, he'd plead with Katsuki to let him suckle on his alpha cock, and it pacified him like a baby. How could he say no?

He still bullied him at school. But now, sometimes he'd drag him into the bathroom.

Make him suck him off. One day he even took Deku's pants off - a first. He didn't peek much that time, adjusting Deku so his thighs touched and urgently fucking between them until his spend coated Deku's thighs and the stall wall.

"Clean this shit up," he ordered as he left.

It was only after that he became more interested in Deku's body. Probably around late middle school. His balls were nice and heavy, the lump at the bottom of his cock growing bigger with age, and his instincts demanding he pop it into something warm, wet, and willing.

And Deku was all of those things. So what would it matter if he fucked him? Same thing, different hole, right?

So that's what he did. The first time, Deku was in the middle of one of those long, slow blow jobs. Katsuki always enjoyed those, let the omega take his time.

He usually wasn't in a rush, and he liked seeing how long he could last and feeling how intense it got. But this time he wanted something more.

"Get up here, Deku," he said. Those half-lidded eyes looked up at him in confusion as he paused his worship of Katsuki's cock.

He wordlessly climbed up the bed, confused as Katsuki climbed atop him, thighs bracketing the omega's hips as he sat on his ass.

"Kacchan?"

"Mmm," Katsuki groaned, feeling the wetness from Deku's hole through his soaked pants caressing his still bare cock.

"I'm gonna give you a treat today, Deku."

He pulled the waistband down below Deku's ass cheeks, admiring their generous curve on his small and scrawny body. Must've been those omega hormones filling him out all nice. And those freckles dotted everywhere.

He gripped those cheeks and spread them wide, eager to appraise the hole he'd ignored for so many years.

It was... pink. A pretty shade that had Katsuki's breath catching, his fingers tracing it and becoming sticky with slick.

Deku gasped. "Oh... Ka-Kacchan, no.."

"Why the fuck not?" he asked, dipping one thumb in. "You've been gagging for this cock since you were a fucking toddler."

But Deku couldn't respond to that question, not with the sensation of Katsuki's digit breaching his hole. That wet hole tensed around him.

"Trying to suck me in, huh, Deku?" he mocked. "Don't worry. I'll give that slutty ass what it needs."

He removed his thumb and replaced it with his cock in one quick thrust. He groaned at the tightness suddenly holding him in a vise grip.

Deku's mouth opened in a silent scream, but Katsuki had one hand shoving his face hard into the pillow for good measure. He didn't need his parents hearing this.

"Fuck, Deku," he snarled. "So tight... won't even let me pull out."

He began to thrust then.

Short, slow experimental thrusts as he enjoyed the new sensation. This felt so much better than Deku's mouth. Impossibly better. And he could have been having it this whole time.

He removed his hand from Deku's head to grip his ass cheeks once again.

"Shit," he groaned in appreciation at the clear view of his cock spearing Deku's hole, rim gripping him every time he went to pull out even slightly. "Such a greedy ass. That feel good, Deku?"

All he heard were sobs through the pillow, which had him tutting in disapproval.

One hand moved to grip Deku by the hair, yanking him up. " I said, how's it feel, Deku. Answer me when I'm fucking talking to you."

It was then he noticed the slobber dripping down the omega's face, soaking the pillow. Deku... he looked /gone/.

Cute little pants and whimpers were the only noises Katsuki could get out of him until a strong arm pulled back to bruisingly spank the omega, shocking a yelp from him.

"How's it feel, Deku?"

"Kacchan's cock," Deku moaned, "Kacchan's cock feels so good. I can't... I'm... I'm..

Ohhhh..." Deku keened, a high and pained sound.

"Ha!" Katsuki laughed. "Come already? God, such a whore for my big alpha prick." He leaned down to lie atop the smaller boy, chest pressed to his back and his full weight bearing down. Deku groaned at the pressure.

He turned to speak directly into his ear. "And you know what, Deku?"

"Nooo..." the omega wept.

"That's all you're ever gonna be," he whispered, a malicious smile quirking his lips. "When I'm a pro, hundreds of miles away fucking omegas prettier and smarter than you...

.... you're still gonna be here. Desperate for my cock. And no one else's. Know why?"

Deku couldn't even answer, but the clenching of his ass around Katsuki's thick cock ensured that his words were doing something to him.

"It's because you were destined to be my fuckhole."

As soon as the word left his mouth, Katsuki was groaning in pleasure. It was coming on fast, and he quickly pulled out to jerk it above Deku just before it spattered all over the omega's freckled ass and back.

"Nnngh... guhh.. fuck, you like that, Deku?"

Katsuki was heaving, exhaustion overtaking him. He collapsed back down upon Deku, enjoying the subtle shaking of his body as it wracked with shameful sobs.

"S'okay, Deku," Katsuki chuckled. "No one ever expected you to be anything else."

That didn't seem to console him.

Not that Katsuki thought it would or cared if it did. Still, he continued.

"Who knows? Maybe I'll take you with me, if you prove you can be anything more than pathetic."

That seemed to quiet the sobs, though barely. His words had him thinking, though.

He truly couldn't imagine a world without Deku. He'd always had Deku around - to bully, to command, to use. It'd be weird to leave him behind. Besides. Deku really /couldn't/ be useful to anyone else. He was bound to Katsuki, though Katsuki wasn't bound to him.

He'd just waste away here until he died. And Katsuki had plenty of uses for Deku, all incredibly satisfying.

He sighed, breath tickling Deku's cheek as he made up his mind. He'd definitely be taking Deku with him.

The decision had his belly warming.

His inner alpha obviously agreed with the him. Now to just keep it from Deku.

Sure, it would cause him a lot of distress.

But distressing Deku was his favorite pastime, and Deku couldn't leave him even if he wanted to.

END.