I forgot where this is from but I had it saved in my documents. I think there was a story behind this but idk just enjoy the smut.

(In this one Dekus a monster fucker and Kacchan just so happens to be a monster)

Izuku didn’t know how he ended up being pinned under this... this hairy monstrosity, who was breathing down against his face. Smelly puffs hitting him in the face, spit trickling down on his face and neck. But... but Izuku definitely was where he always wanted to be.
He had known from a very young age that he was different than the other humans in the small village he grew up in. Being more interested in the mythical creatures that lived in hiding in their world. Wanting to know more about them. His desire for knowledge turning into a desire to see one, touch one, eventually to his sexually awakening, the older he had gotten.
Izuku shivered as the body looming over him moved its snoot against the side of his neck, pushing it against the crook and taking a deep breath of his scent.
He could feel his soft cock slowly hardening under the treatment and... this was most definitely the wrong time to be horny. Just one snap of those razor-sharp teeth and he could be death. But here he was, trying to wilt down his boner. Izuku tried to calm down, taking deep breaths. Though he couldn’t stop the whining that left his parted lips as he felt the cold, wet tongue of the beast licking the skin behind his ear. Sucking on his ear lobe.

“Please. Please don’t eat me.”

He whispered more to himself, assuming the beast wouldn’t be able to understand him. He assumed wrong.

“Oh I will definitely be eating you up. Don’t worry you will like it, little one.”

Mouth agape and eyes wide open Izuku stared at the beast who was smirking down at him. Maybe he was dreaming? It wouldn’t be the first time, neither the second, for him to have this kind of dream but this felt so much more real than his other dreams. Or maybe the beast had already killed him and this was his own heaven... or hell. Who knows?

“I can smell your arousal, you know. And it’s mating season so don’t blame me about what’s going to happen with that sweet ass of yours.”

That day Izuku lost his virginity.
He sobbed around the beast’s, Bakugou Katsuki he learned later, fingers while he, as promised, ate his ass out. Preparing him with too much spit, his tongue and fingers until Izuku felt the spit trickling down his thighs like slick. Until his hole was clenching down at the intrusion, trying to suck it in deeper. Until he was begging to feel his cock inside. And what a gorgeous cock it was. Entering in one hard thrust it left him breathless. Without time to adjust Katsuki was pounding into him.
Izuku didn’t know how much he came that day or how long they were going at it. At one point he had lost conscious and woke up later with Katsuki’s cock still buried deep inside him. But instead of the dirty forest ground they were on, they were on top of a soft bed and Izuku felt clean. Katsuki had cleaned him up while he was unconscious.
Katsuki himself had wrapped his arms around Izuku, holding him tight against his hairy chest and was sleeping peacefully behind him.

This went on for days, weeks... Izuku couldn’t really tell how long time went by while he was locked up in Katsuki’s bedroom. He was only allowed to get up of the bed, ‘den’ Katsuki had called it, to go to the bathroom or eat something. And any time Izuku was walking the short distance to the on-suit bathroom or to the table, already set up with lots of food which Katsuki probably brought in while Izuku was sleeping, the beast of a man was looming over him. Not letting him out of his eyes for even a second. As if Izuku would run away. Never mind his shaking legs, sore body and overall exhausting he felt like this was a dream come true.
Any sane human being would try his hardest to escape the grotesque monstrosity that was Bakugou Katsuki. Looking more like a mix of a lion and a wolf on two legs, easily over towering Izuku with his build and manhandling him into submission just the way he loved. Any sane human would have been scared of him. But not him. On the contrary Izuku couldn’t get enough of Katsuki even though they had sex every day. Repeatedly. He couldn’t get enough of that big cock, all angry red and veiny with an even bigger knot at base, pounding into his tight ass. Destroying him daily. Practically rearranging his guts with how big it was. Every time Katsuki bottomed out, thrusted into him, his stomach bulged out. He could see the outline of that pretty cock on his lower abdomen. It was delicious.
Izuku wished that the mating season never ended so he could stay here with Katsuki. Be his toy. To be used to his heart’s content.
Though there was one thing that bothered Izuku about their ‘arrangement’. They hadn’t kissed at all. He craved to feel Katsuki’s lips on his. Craved to feel that long, wet, rough tongue going down his throat and fucking his mouth in the same rhythm of Katsuki’s hips thrusting into him. Wanted those sharp teeth to bite his lips bloody. But Katsuki refused to do so. No matter how much Izuku begged him for a kiss, just a short peck during the sensual foreplay, Katsuki never gave in.

Izuku had woken up alone. Shifting on his back and winced at the sharp pain he felt down his spine because of earlier activities. Cum drippled down his used and puffy hole, making him gasp.
Lately Katsuki had stopped cleaning his cum out of him, mumbling something about how it should take this time and Izuku... he didn’t have the heart to tell him that as a human male Izuku couldn’t get pregnant. Though he still angled his hips up, shoving a pillow underneath to make sure not a drop escaped. Let the man have his fantasies since he fulfilled every of Izuku’s fantasies. Even if he was been denied a kiss.
When Katsuki finally returned, unlocking the door to the room, Izuku had already taken another nap, cleaned himself up in the on-suit bathroom. He had to get rid of the dry cum inside him sadly but he would be filled again soon. He had found some fruits left behind on the table and eaten them to get back some of his energy.
He turned to the door, putting on his best pouting face, and tried his best to show Katsuki how dissatisfied he was with being left alone for a whole day. Katsuki had the audacity to not even look apologetic. He snorted at the view Izuku made with all his naked glory and locked the door behind him.

“Did you miss me, little one?”

Izuku couldn’t stop the whine escaping him. The growling undertone coupled with the look Katsuki was giving him made him weak. So weak.
Katsuki wasn’t wearing any clothes of course. His cock already hard, curving upwards towards his stomach. Izuku’s mouth watered, wanting to get his lips all over that. He was hypnotized, following the small pearls of precum leaving the slit and slowly gliding down the length until they disappeared from his view, probably dripping down on the ground. His green eyes snapped up to Katsuki’s face when the other was already so close, he could have leaned down to take the head of his cock in his mouth and suck the droplets of precum so they wouldn’t go to waste.
Katsuki was smirking down at him knowingly. That narcissistic bastard! A bastard he wanted to feel inside of him. For the rest of his life if he had any say in it.

“Do you see something you like?”

Izuku snapped his mouth close, swallowing down the saliva that had pooled in his mouth. He forgot his goal to berate Katsuki for leaving him alone with nothing to do. With nothing to entertain himself. Right now, Izuku just really wanted to taste him. So, he did. Izuku leaned the few inches towards him and put his lips around the head of Katsuki’s dick. Wrapping his tongue around it and lapping at the steadily dropping precum. Taking in even more of his cock as Katsuki groaned above him. Motivating him to suck even harder.

“That’s right! Just like that. Get me wet to mount that tight ass of yours, little one.”

It was a demand. A demand Izuku couldn’t and didn’t want to deny. He relaxed his throat as best as he could and took the rest of Katsuki’s cock in in one go. Sucking and licking until he felt his breath going short. He gripped the base with one hand, his fingers not even close to touching, and slowly moved his head up and down before taking the cock out of his mouth to take a big breath. He looked up teary eyed. His whole body shivering at the hungry look Katsuki was giving him.

“Good job! Now on your hands and knees. Present yourself!”

In his eagerness Izuku almost stumbled over the covers. But within seconds he was on his hands and knees, lowering his upper body, ass up in the air. He turned his head to the side so he could watch Katsuki inspecting him. See the hunger in his eyes, how he licked his lips in anticipation.. it was impossible but Izuku felt wet. He felt like slick was dripping down his thighs. Katsuki put a hand flat on his back, joining him on the bed. With his other hand he was lightly brushing up Izuku’s thighs, the spots where he had felt the phantom slick dribbling down.

“You are ready to be bred. To carry my children.”

Katsuki was behind him. The head of his cock teasing Izuku’s twitching hole. When both of them pushed against each other at the same time the head of Katsuki’s cock easily slid into Izuku. Without any preparation.
Izuku gasped loudly, moaning even louder when Katsuki pushed down more. It felt more intensive than the other times. Izuku’s mind fogging. Drool slipping past his lips. By the time Katsuki bottomed out Izuku was a mess already. Mumbling incoherent things. Begging for more. And clenching around that delicious cock inside him. He might have cum already, he didn’t know. All he knew and felt was pleasure, was Katsuki around him, moving his hips in a slow rhythm ang grinding down on him.

“You are doing so well, Izuku, taking me in so well. Milking my cock with that greedy ass of yours. Do you want it? Do you want me to cum inside until you are plumb and round with my spawn?”

Izuku’s leg quivered, almost giving in. He needed more. He wanted more friction, for Katsuki to go in harder. He wanted to see Katsuki’s unhuman face while he pounded into him. He wanted... he wanted a kiss.

“Ka-Kacchan, please.. kiss.. please.”

Katsuki stopped moving, contemplating, before he pulled out of Izuku, who let out a whine, easily turning him around onto his back and sliding back home in one hard thrust. Gaining in speed as he saw Izuku’s blissed out face.
The fertile smell was too much for Katsuki he wouldn’t be able to keep up for longer. Had prolonged their mating for today for too long. Growls and whines, the sound of slick coated skin slapping against skin, filling the room as Katsuki folded Izuku in half. Izuku’s knees easily touching his ears. Katsuki’s hips stuttered. He was still hesitant about a kiss but the moment his knot slipped in, inflated impossible big, flooding the already cramped insides of Izuku with an unhuman amount of cum, making his stomach bulge even more, Katsuki leaned down and claimed these soft lips in a hard kiss. All tongue and teeth. Scraping Izuku’s skin and tasting his blood.
Finally. Izuku clung onto Katsuki, holding him close and returning the kiss just as aggressive as Katsuki was kissing him. He had waited so long he wouldn’t let go for a while. When Izuku opened his closed eyes ajar his eyes almost bulged. He accidentally bit Katsuki hard and tried to get away. If it wasn’t for the knot up his ass, he probably would have success.

“What the fuck is your problem, bitch?”

“Who... who are you?”

“Huh?”

Instead of the face of a beast, Izuku was greeted with the face of a handsome young man who looked very much human. But. But he had Katsuki’s red eyes. The same scowl. And he was very much stuck to Izuku via ass-to-knot. It could only be Katsuki. How was that possible? Had Izuku had hallucinated all this time and Katsuki was a human all along? But he still had a knot...

“Shut up! You are mumbling.”

Izuku covered his mouth with both of his hands, staring expectantly at... Katsuki? Waiting for him to explain what was going on.
Katsuki wasn’t really in the mood to explain anything. He had wanted to claim his mates lips some more. Ground into him until he is milked dry. He sighed. Grabbing onto Izuku’s hips so he could potion them into a more comfortable position in which they could talk properly. Katsuki leaned against the headboard of the bed with Izuku in his lap, pushing his nose into the crook of his neck to take a deep breath of his mate’s scent.

“Calm down, Izuku, it’s still me. Katsuki.”

Skipping the parts of him being scared that Izuku’s kiss wouldn’t be the one to break the curse thus making him not Katsuki’s true mate even though Katsuki imprinted on him the moment he had seen him. He explained how he had been cursed long time ago by a witch because he kind of upset her by calling her anything but her name. That how he still was a so called ‘beast’ even though he looked very human and would keep his knot, to which Izuku cried in relief.

“How the fuck could you not know that you are part of the faeries? You reek of them and you are a male with a womb. Human males don’t have a womb.”

Izuku stared at him with his mouth agape. Glancing down at his bulged stomach before looking back at Katsuki.

“Excuse me? My mom is a human and I think I would know if.. I had a womb..”

“Well, I said “part” not “full” faerie.”

He smirked down at him.

“And you will know and see that you have a womb soon enough.”