Fanboy & Zero AU #bkdk
CW: NSFW. Kink exploration. Humor. Audience participation (choose your own adventure of sorts). Established Relationship.
--
It was bound to happen that at some point Katsuki was going to confront Izuku about all of his thirst posting over the years.

Katsuki had long since caught up on every one of Fanboy's hundreds of posts. They ranged anywhere from professional opinions on heroes to him drooling and begging for GZ's dick. It was easy to see what days Izuku had been feeling particularly horny.

Katsuki had also seen Izuku's fap folder that he supposedly had hidden deep in his computer. It had revealed some... interesting things to his eyes. Mostly that people made a lot of goddamn fanart of him. Including blowing his dick up to crazy sizes.

He and Izuku had been married for almost a year now and they were just as smitten as they had been since the days they had only communicated through the computer and phone screens. Their sex life was amazing in between Katsuki's work schedule. They were completely in love.

Which is why Katsuki thought it was about time they started mixing things up a little. They'd already tried a couple of new things - toys, and mild bondage for example - but for the most part they'd been pretty vanilla despite Izuku's fantasies.

See, it wasn't that Katsuki didn't have fantasies about things to do with Fanboy. It was just that Katsuki wasn't exactly... interested in putting a lot of effort into that stuff. He loved having just him and Izuku, bodies together and moving against one another.

Sue him if he enjoyed just that. It was usually enough for him. Even if it was just a quickie, he didn't think he would ever really get his fill anytime soon of Fanboy crying out his name and praising him. He didn't know how he had lived without it before.

God, just picturing it was enough to get him going. Fanboy spread out on his bed in his colors, his shirt hiked up to reveal his rosy brown nipples and hard cock. Ass glistening with the lube he'd already prepared himself with. Cock ring on while waiting for Zero in him-

Whoa, wait, he was getting distracted. He needed to focus. Goddamn sexy Fanboy. He wasn't even home and Katsuki was fucking hard. Katsuki was still on a trip and was supposed to go home soon. He'd only had Fanboy's texting to get him by. The anticipation was killing him.

Vanilla sex aside, Katsuki figured it was time to reward Izuku for sticking by him and being, well, the love of his goddamn life. He deserved to be treated well. And that included indulging in some of his kinks. He claimed he wasn't kinky, but Katsuki had read his blog dammit.

Admittedly not everything on there was bad. Hell, some of it could be exaggeration. He didn't exactly know for sure what Izuku wanted, so he had to ask. There were plenty of things Katsuki could easily do, but he figured he would let Izuku take the lead on this.

He waited until he was finally back home and had Izuku in his arms. He had the next day off which meant a long night of indulging in his husband. Katsuki kicked Sexy Pillow Ground Zero-sama 2.0 from the bed and ravished his husband slowly and passionately until Izuku was a mess.

"I love and hate when you go on trips." Izuku told him, petting his neck and shoulder as Katsuki pressed slow kisses to his throat up to his ear. He shivered in his grip. Their arousals were ignored in favor of indulging.

"Yeah?" Katsuki asked. "How come?"

"You always come back to me like you haven't seen me in forever." He laughed but sounded thrilled nonetheless. "I never get used to it."

"Good. Don't get used to it." Katsuki captured his lips again before he pulled back to hover over him instead, watching him.

Izuku blinked at him. "What's up?"

"Got some questions for you."

"Oh no, it's serious Kacchan." Izuku teased, but he sat up on his elbows. Katsuki sat back properly. "What is it?"

"I was thinking we do some new stuff."

"New stuff?"

"Yeah. Like..." Why did he feel weird bringing this up? How the fuck did Fanboy look so innocent when Katsuki knew he was a horny little shit? Hell, his dick was still tented in his boxers. He shouldn't look so cute right now. He hated being in love. He also loved it. Damn.

"Kinks." He finally got out. Izuku's eyes widened. "Let's try some of the shit you drool about on your blog."

"REALLY?!" Izuku yelled, startling both of them with his excitement. His eyes sparkled. "Can we really?! You want to?!"

Katsuki scowled. "Sure."

"I didn't think you were interested! Oh my god, what do you want to do?!"

"That's up to you, idiot. Why do you think I'm asking? I don't know anything about half the stuff you bring up. Or what you even like. Do you seriously want me to choke you out?"

Izuku flushed. "Oh, um, I mean it's a turn of phrase-"

"I'm not interested in doing that." Katsuki told him right away. He had promised not to hurt Izuku anymore, and the thought of doing something like that reminded him too much of when he had bullied Izuku.

"Okay. I never really thought about that anyway." Izuku rubbed at the back of his head. Katsuki couldn't tell if he was lying. "...So it's my choice?"

Katsuki nodded. "You choose. Just know that some stuff we may need to get things for."

"Got it. Okay, let me think..."

(Which kink does Fanboy want to try out first?)

"How about we try out ABO?"

Katsuki's mind flashed through a series of fanfiction that'd he'd read and seen. The mental image of a knot the size of a child's fist at the end of a dick that only a horse could have. The scenting and the biting. The claiming and the bond.

Then he saw Izuku on his back, stomach slightly rounder as he was pregnant with Katsuki's child. His legs and ass shiny with slick as he begged for his cock and his knot. Izuku presenting himself for Katsuki and crooning for his Alpha and needing to be fucked by his Alpha.

Izuku had that slightly mischievous look on his face that pissed Katsuki off to no end. The asshole was messing with him. Katsuki refused to admit he had ever read ABO even though they both knew he had.

He scowled at Izuku. "I'll fucking kill you. Try again, asshole."

(Lol, you guys thought it would be that easy? This is a comedy AU.

Also I don't have time to write more right now so one more vote)

(Oh shit I called it too early what the fuck)

(I had an entire thing done for hero/villain and yall came out of fucking nowhere in the last 4 minutes and voted for ABO what the actual fuck alright)

"Come on." Izuku crawled across the bed and into Katsuki's lap. He purposely wiggled against the semi that was only beginning to wilt in his sweatpants. Katsuki hated how easy it was to get it back to attention, but his half-naked husband did well with it.

"I'm being serious. You're interested in it. I'm interested in it. Why not roleplay?"

"My dick is big, but I don't have a fucking horse cock and I don't have a tumor at the base of it either." Katsuki crossed his arms, refusing to be cajoled.

"Who said you would top?" Izuku asked with a frown.

"Every goddamn fanfiction about me in an ABO setting."

"I've seen ones where you bottom to Kirishima."

"DON'T MENTION SHITTY HAIR WHEN YOU'RE ATTEMPTING TO FUCK YOURSELF ON MY DICK THROUGH OUR CLOTHES, IDIOT!"

Izuku stopped grinding against him just for the sake of being able to talk seriously. "I could be an Alpha if you don't wanna do it."

"There's no way in hell I'm an Omega."

"But I'd be a great Alpha!

"I'll be the best goddamn Alpha!" Katsuki announced with a growl.

"Prove it then." Izuku raised his chin a little. Katsuki snarled and shoved him back onto the bed.

"You think I couldn't be?" He said lowly. Izuku thrilled by the angry and determined look on his face. His Zero. He was sexy as hell like this.

"You're an amazing Alpha, Zero." Izuku murmured, easily switching gears as he kissed Katsuki. He lifted a leg to hook over Katsuki's hip and sighed with pleasure. Katsuki blinked at him, eyes widening at the change. "I've been waiting for you to fuck me."

Katsuki hadn't really caught on yet. His anger shifted into his usual cocky confidence when Fanboy praised him. He rolled his hips against Izuku's with a low hum. "Been dreamin' about your ass since before I left, Fanboy."

"Omega." Izuku corrected, grabbing Katsuki's hands.

He linked their fingers so that Katsuki was pinning him down. "Your Omega."

Katsuki mentally flailed. Oh shit. Oh shit, they'd already started. What the fuck was he supposed to do? Growl? Bite his neck?! How the fuck did ABO roleplay even work? What was foreplay?!

"My heat'll be coming on soon, Alpha. Is that why you're here? Did you smell me? I thought I had locked my door, but I didn't expect to find a strange Alpha in my bed." Izuku continued, trying to help him. He let out a shuddering breath, leg pressing Katsuki down more.

Katsuki only made a face. "Thought we'd already be Mates."

"I mean, we can do it that way." Izuku said.

"You want me to fucking rape you during your heat?"

"NO!" Izuku's head thumped back against the bed. Why were they discussing this?

Katsuki scowled. "I'm trying to get into character!"

"Have you only been reading the really questionable ABO fics?"

"Fuck you, I don't read fanfiction! I only see bits and pieces on your blog!"

"I /want/ you in my nest. I'm playing coy, Zero."

"You don't know how to play coy to save your damn life. I've seen you fingering yourself on the bed as a seduction technique."

"Oh my god, Kacchan."

"I ain't gonna act out that illegal shit. If I'm gonna fucking bond you, it's gonna be cuz we both want it!"

Izuku closed his eyes briefly. He loved Zero with all of his heart and soul. That included the sometimes idiotic parts too. Kacchan was his wonderful husband that sometimes had really weird and strict morals. He couldn't hate him for that.

"Okay. Okay, let me try again." Izuku's leg slipped from Katsuki's hip to cage him in between his bent legs. He had been excited for a random encounter kind of deal, but a loving relationship worked for him too. He wanted to think of something good.

(How should the Omega approach it? "Heat is coming up and I want to finally bond with you and have your pups" (Romantic encounter) or "Driven crazy with lust and desperate for a knot" (Lusty encounter)?)

(I'm not going to ask for opinions at every turn, btw, just where I'm actually conflicted or it's funny for the plot of the thread lmao)

"My heat is coming." Izuku murmured, arms wrapping around Katsuki's neck to pull him in. He kissed the corner of his mouth. "I've been waiting for it. I've been wanting your pups, Alpha. Lets bond and make a family together. I need you."

Katsuki did not move for a moment. Izuku blinked and pulled back to see Katsuki staring at him with a wide-eyed slack look. He only stared. Izuku waited and then got a little concerned. "K... Kacchan?"

That snapped Katsuki back to it. His cheeks turned red and he sat up.

"Holy shit." His hand covered his mouth as he attempted to hide his embarrassment. Izuku shifted nervously. He hadn't seen this kind of reaction out of Katsuki since their wedding. "What the fuck."

"...Too weird?" He asked. He found it weird to be talking about getting pregnant.

But it was part of the quirk of playing ABO. The thrill of fucking an Omega intent on making them pregnant with little babies even though they're a male. At least, that was the interpretation Izuku got out of the few ABO fanfics he'd read.

"It's..." Katsuki shook his head. Then he dove back in to hide his face in Izuku's neck. "Fuck, that was effective."

Izuku's skin felt like static ran across it. Katsuki's hands slid along his chest as his tongue lathed against his neck. "Really?" He asked.

"Fuck yes. I've been hoping you'd invite me into your bed, shitty Omega." Katsuki's teeth scraped against the side of his neck. Izuku shivered as his hands stroked his neck and back. "You've been needy as fuck for my knot, huh?

So much for Katsuki pretending he'd never read ABO. He knew just the right things to say. Izuku grinned where Katsuki couldn't see it.

"I've wanted it badly." He moaned a bit as Katsuki's hand slipped under his boxers to cup his hardening cock and his balls. "So badly."

"You're already so wet for me. It really is close to your heat, isn't it?" Katsuki lifted his head and gave Izuku that devastatingly hungry smile that never failed to go straight to his dick. It hardened under Katsuki's hot hands. "And you want me to bond you?"

"Yes!" Izuku nodded. Katsuki's finger circled his entrance but didn't press in. Izuku knew he needed to actually grab some lube, but he needed to taste that smile. "Make me yours, Kacchan."

"You're already mine." Katsuki growled. Izuku captured those lips.

He was lost in the sensation as Katsuki stroked him to fullness, fingers playing against his slickening head as his tongue coaxed him to melt with familiar movements. He could smell Katsuki's natural musk.

He loved Katsuki's scent, but imagining that it was stronger and was causing him to be turned on more only made him groan.

"Lube." Izuku whispered when he pulled back to kiss at Katsuki's jaw.

"Got it." Katsuki pulled away to go fetch it. Izuku ripped his boxers of swiftly.

"Alpha~" He whined, shifting against the bedspread. He stroked himself teasingly when Katsuki stumbled in his haste to retrieve the lube. "Fuck, I can't wait for you. I need your big cock in me."

"My massive horse and tumor cock." Katsuki couldn't resist saying.

"Your massive horse cock fucking my uterus!" Izuku responded, crying out dramatically. Katsuki collapsed on the bed, shoulders shaking from the laughter he buried into the covers. Izuku threw an arm over his own eyes as he laughed as well.

"I'm gonna fuck you so hard with my gigantic dick and lock myself to you for hours at a time!" Katsuki threw back at him as he brought the lube. Izuku adored the playful side of Katsuki that came out once in a while. His laughter wasn't exactly the sexiest thing but his face was.

"I want to feel your head so far up my ass that I can't breath without feeling it." Izuku squirted some of the lube into his hand and prepared himself as he and Katsuki kissed once more. The Alpha slipped down to lick his nipples and his chest as Izuku opened himself up easily.

He mostly only needed the lube. His ass was used to having things inside it by this point and despite the silliness he was aroused as hell.

"I'm gonna make you shit babies, Fanboy."

Izuku couldn't fucking handle it as he cackled at the thought.

"Dammit, Kacchan!"

"Move your hand already." Katsuki continued to grin as he yanked Izuku down to meet him. His sweatpants were pushed down enough to expose himself as he swiped his hand along the extra lube to slick himself up.

"This is so not sexy."

"You say that, but you're hard as fuck for me."

"I'm always hard for you."

"Shit, have I told you I love you today?"

"Yes, but I love hearing you say it."

The dorks shared quick, soft glances before they got serious again. Katsuki pushed into him.

"Fuuuuuck." He groaned. "I love you and your /ass/. Shit, I could stay here all day."

"Knot me and you can."

"You're not in heat yet, bitch."

"That's Omega bitch to you, Alpha."

"God, shut the fuck /up/." He laughed as he kissed him.

It was probably one of the more ridiculous times they'd had sex as Katsuki's hips rolled and his cock fucked Izuku. It was sweet as the two attempted to use the ABO names for each other, but it fell away as they both actually became caught up in the moment.

Katsuki loved hearing his names from Izuku's lips. He'd missed them over the two weeks he'd been gone. He could only focus on the sensation of Izuku pulling him in. He was better than any cocksleeve both of them ever had. His lips were much sweeter too.

"Shit. Shit, I'm gonna cum in you hard, Fanboy. Haven't had a good orgasm in weeks."

"Come in me, Alpha. I want your pups! Don't forget to bite me!" Izuku cried, knees practically to his ears as Katsuki bent him in two. He was so goddamn flexible, it killed Katsuki to see.

"Holy shit, fuck off with that already." Katsuki listened, though, and bit Izuku's neck hard as the man screamed and they both came. Katsuki shuddered as he milked himself a little longer, but didn't really get to enjoy it as Izuku shoved him away from his neck.

"Ow." He made a face. Katsuki frowned and glanced between them. This wasn't usually how Izuku acted after sex.

"You didn't really like that, huh?"

"The bite kind of distracted me at the end." Izuku confessed. He touched the bite gingerly. Definitely bleeding.

"Sorry." Damn, that sucked. Izuku usually liked being creampied once in a while. Guess he fucked that up.

"We kind of lost it in the middle there." He said as Katsuki pulled out of him and helped to lower his hips back to the bed.

"I lost it talking about horse dicks."

"Me too." Izuku paused, and then began to snicker again. Katsuki sat back and tucked himself back into his pants. "I kind of want another shot."

"At the ABO thing?"

"No, at the kinks thing. If that's alright."

Katsuki shrugged. "Up to you. You're into the kinky shit."

"Our marriage isn't so old that we need to spice things up a ton. But I would love to do more fantasies. ABO was more your thing."

"THE FUCK IT IS!" Katsuki snarled at him. Izuku didn't fight back.

"I have a couple ideas. But right now I mostly just want a shower and some food."

"How about we go out tonight?"

"That sounds great."

(TBC tomorrow after I get home from work. I'll post the kink vote now, though.)

(Which kink does Fanboy wanna try next?)