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Izuku was still a small boy when his father introduced him to the world of humans, they all walked the same earth after all.


Their castle in the giant forest of mysteries, humans dared not traverse into it. In fear of the creatures that lived there, in fear of the demon king whose castle was taller than any man-made structure. The forest dead center of the human's world, no human knew exactly how large the forest was, how long demons had lived there. Not a single human knew that the demon king and prince were as gentle as could be.


Hisashi helped his son with a spell, to hide his little green demonic marks and to hide his twisty childish horns, to turn his claws into chubby little hands. Izuku looked like any human boy, save for his excited tail, how heavy it swayed side to side. Izuku was too young to learn to hide that much yet, but a cloak would do the trick. Hisashi held Izuku’s hand as the demon king opened a portal, a little bit away from a human village. Hisashi wanted to show his son the wonders of the humans, how they thought and how they celebrated with festivals and food.


“What food do they eat? Goblins? Sun ogres? No, they probably eat selkies, the ocean is close by!” Izuku looked around excitedly, taking in the sight of the oncoming village. Hisashi’s little spell broken quickly and the boy's marks appeared on his temples and his cheekbones. Izuku’s father sighed and placed another spell, a little more magical power behind it so that it would hold longer.


“I think mostly  they eat fish or chicken, Izuku.” Hisashi chuckled as his son pouted, he knew that answer was boring to his curious child. “Do you remember those large creatures; cows?”


“They’re not that large! I could pick one up, remember?”


“Yes, Yes, I remember. Though, humans can’t pick them up.” Hisashi stepped to the side, a horse-pulled wagon passing by them with leisure, Izuku’s eyes widen as he watched his first human sit lazily on the seat of the wagon. “They drink the milk of the cows, then humans eat the cows, cook their meat and such.”


Izuku made a face as he looked from the human to his father, the cows were so pretty when one wandered into the forest. At least the meat demons ate came from brainless demons, livestock that reproduced with the purpose to be eaten. Izuku still remembered petting the cow, staring into her beautiful black eyes and blinking when she blinked at him, her long lashes tickling his face when he got insanely close to her long face. She was beautiful, large and brown. He remembered how his mother demanded he put the cow down when he picked her up and ran to the castle with her.


Izuku found himself asking. “Does it hurt them?”


“If the butcher isn’t careful, yes, it hurts them.”


“Then, why do they do it? I thought humans were nice, father…”


Hisashi pursed his lips and thought for a long moment. “Humans are like us, they can be gentle, they can be cruel, that’s why you mustn’t judge one on the actions of another.”


“But if all humans eat meat then-“ Izuku’s round eyes found themselves attached to the town, how ribbons flowed off the roofs of houses, beautiful omegas and betas in dresses and gowns. Alphas in their best clothing. Izuku tugged on his father’s hand and bounced in place happily, he wanted to get closer and witness more of the human's village. His moments of cynical speculation forgotten quickly.


Hisashi followed Izuku where the boy led, young women placing necklaces of flowers around their necks, a red crown of flowers for Izuku. The boy smiled at them and sook they found food. Izuku following his nose until they reached a station, grilled duck strips for sale, just a piece of copper for two servings. Hisashi paying a piece of copper for a delicious treat for his son, Izuku’s fangs digging into the duck. Hisashi doing the same, matching his son's wide grin. His son's cheeks pink and he was glowing in the sun that light up the festival.


Izuku was literally glowing.


“That boy!” The merchant exclaimed, gaining attention from other humans who were close by, all of them looking in Izuku’s direction.


Hisashi pulled Izuku’s hood over his head, hiding his son’s glowing marks and sparkling green eyes. The child was growing stronger by the day, Hisashi’s spells weren’t working like they used to. Evidence of how Izuku would become the demon king, the child’s magical power already on par with his father’s. Hisashi picked Izuku up, the boy protesting as the sudden moves made him drop his food. Hisashi hastily walking away but he could hear the beginnings of angry murmurs, of scared crowds, of the demon child. The crowd turning from festivities to anger at the demons who entered their tradition.


“Izuku, do you remember how I said some humans are cruel?” Izuku nodded in confusion, he hugged his father’s neck, holding on tightly as he was jostled. “You can not show the humans how you look, they fear the unknown, fear those who look different.”


Hisashi hugged Izuku tighter as the boy's eyes watered, the poor child confused but his father's words scared him. The demon king made sure to start teaching Izuku everything of the human world when they returned to the castle, he didn’t want Izuku to be like his father. The previous demon king feared the humans, never left the castle, harbored Hisashi until the day the old demon died. Hisashi didn’t want Izuku to fear anyone or anything, he wanted him to remain curious until the end of his life.


Izuku began to cry for his mother, he had enough of the human world for his first day amongst them. Hisashi carried his son out of the village, Izuku’s tail curled under him in his lap. Once out of sight of the humans, he opened a portal, stepping through it and he stood in the forest of mysteries, close to the castle, a small walk to ward off any fear Izuku held onto, to air out the stressed scent Hisashi carried.


Maybe their day hadn’t turned out exactly how he had envisioned it.




Izuku never asked Hisashi or Inko again to take him to the world of humans, almost as if he wasn’t interested in meeting them. He kept his nose buried in history books of the strange humans. He studied his magic and when he presented as an alpha, he worked with his magic on shapeshifting.


Hisashi marveled in how his son could turn into a fire-breathing dragon with a few incantations. Izuku standing with a rag to cover his bits in front of his mother whose eyes filled with tears at how quickly her only child was growing up.


Izuku would make a great demon king. Now if only he was more interested in meeting humans than learning about them from books.




The humans had done it again, ventured too close to his territory, taken his animals to kill and go feast on. Granted, they were cows, pigs, and horses that Izuku took from a village because of how dirty they kept their pens, how sickly the animals looked in the hands of the human. The human soldiers injured a couple of the nymphs that giggled and played in the ponds near his castle, they had tried to run and their mossy hair was yanked back. Despite being a demon himself, Izuku thought of them as the real savages. He had seen how they treat their own kind, the power struggle, the poverty, the pain of mothers and children. Even worse amongst omegas, how they were sold and taken by the next brute they stumbled upon.


He had thought many times of conquering the human world. Izuku had thought for years on end how he would create a new structure for each gender, that omegas and betas alike could choose who they mated and bore children for. How alphas would be put in their rightful places, brought down from their accidentally bitty place.


Each time, something one of the idiotic human kings making a little more hatred for the humans fill his demon heart. His father would scold him if he could hear what Izuku thought.


He knew their primitive tongue, listened carefully as they made crude jokes at his translator, Shouto. One of the only half-demons who had survived long in the human world, finding refuge in Izuku’s kingdom. The demon boy scowling at them, though their words persisted.  Izuku decided to let them continue to suffer, he cared little, only wanted to help in a way that would profit him the most. Help himself in a way that they would stop raiding his luscious lands, to stop them from hurting the creatures of his kingdom.


His hand laid on the nymph's cheek, her soft blue skin warm under his hand, a nasty gash on her cheek. Izuku’s hand glowed for a moment as he healed her, she bowed her head and ran over with the other water creatures. He watched at how happily they took her back to the waters. How could humans see those peaceful beings and think immediately that they were harmful, think to even harm the nymphs?


Every year the humans grew braver, settling their villages closer and closer to his forest. He had commanded long ago that as long as the humans did not enter his lands, they should not be harmed. This time they escaped, most of them at least, his furries beasts eating away at the remains of armored soldiers. He picked up a broken chest piece, he recognized the sigil that was pressed into the metal, a kingdom only a moment away by the portal. Days away by horseback for those soldiers. Izuku would wait until they returned to their kingdom, he sent three-eyed crows to watch the men. They would notify him and when they did, Izuku would stand before their old king and see what could be fixed.


Though, Izuku had to admit…


He mostly just wanted to cause havoc.




“Your soldiers have stolen from us. They have hurt the creatures of the Demon Kingdom.” The demon boy loudly said, he stood to the side. Izuku and the human king staring face to face. The man on his throne, Izuku standing nearly 30 feet away. The guards and knights stood too close to their cowardly king, even if they tried to protect the old man, they stood no chance against the demon king.


The old king was pissing himself, fear so pungent that Izuku wished to gag. He had opened the portal in the center of the throne room, the old kings scared to cry and the gasps of the room were what Izuku he heard first. His green eyes surrounded in black, his twisted black and greenhorns large and powerful, his demons armor, his magical power. All of it letting the crowd know exactly who he was, the king said nothing as the demon translator began to speak.


Tell him he must pay a price, I won’t tolerate the humans trespassing or stealing from me,” Izuku spoke in his native tongue, amusing in the least how humans eyes bulge at possibly hearing a high born demon speak. The boy nodded and repeated it to the human king, who stumbled over his words.


“The men who trespassed will be punished! Please, I ask you to leave us, my people have done nothing wrong!”


Shouto made a show of speaking in a demon tongue.


“He’s groveling, I think you should kill him, he reeks of livestock.”


“Now, now, tell him I’ll return during the next full moon. That he offers what he deems worthy for the crimes of his soldiers.”


Shouto scowled and told the human king, the old man stuttering and sweating as Izuku and Shouto walked through a portal. The demons left them all alone, heavy thoughts on what would even be worthy as payment for a demon king.




Izuku did as he promised, he returned the night of the full moon. The king had amassed a large pile of worthless golds and silvers, horses and cows. Izuku sighed and let his eyes wander over the pile.


Tell him they’ll burn tonight…”


Shouto nodded and told the human king who cried out, shaking his head.


“Wait! Please! We offer one last gift! We hope it is to your liking, King of Demons!”


The king waved over some guards, who nodded and left Izuku’s sights. The alpha men return quickly, they dragged a human boy, who is tied in ropes, dressed in sheer clothing, gag over his mouth but the way he pulled and resisted against his restraints had Izuku guessing what profanities the boy would shout. Though, the captured boy was a beauty amongst every human present.


Blond as the sun, eyes red as blood.


A human slave. Recently captured by the looks of the marks on his wrists, the marks on his ankles. Izuku can already smell that the boy is an omega as well, no older than 15 or 16 human years.


The human king thinks he has pleaded the demon king with the offering of an omega, he had assumed correctly in guessing Izuku was an alpha.


Izuku wanted to rescue the omega, if there was something he despised more than having his territory trampled on. It was the mistreatment of omegas, such beautiful and gorgeous creatures treated like animals, like breeding livestock.


“He is untouched! He will do well to please you!”


Izuku growled at the human king who got too close to the human boy, anger as his fangs dug into his lip as the old man grabbed the slave's chin roughly to properly show his face to the demon king.


Izuku moved in a swift motion, the human king’s hand on the floor. The human king screaming and holding his handless arm, guards drawing their blades but they did not move in advance of the demon king.


The slave boy stared up at him, red eyes continuously glaring. Izuku grabbed the boy's restraints and opened a portal, his words reaching Shouto.


“Burn it all to the ground.”




The boy fought back when a couple of servant demons took his clothes off, stripping him for a bath under Izuku’s command. Izuku couldn’t help but be a bit amused, usually, humans were frozen with fear.


“Get off me! Don’t touch me!” The boy was relentless and one of the servants gave Izuku a deadpan look. The demon king nodded and waved them away, the human boy scurrying to pick up his clothes. Izuku touched the tub with his clawed hand, the water was warm but it wouldn’t stay like that for long. The blond kept Izuku in his sights, watching his every move, pressing himself against the wall as the demon king came closer. “D-Don’t touch me!”


Izuku touched him anyways, letting droplets of water touch the boy's cheek. The blond blinked and slapped the man’s hand away, glaring at him and rubbing his wet cheek.


Izuku tilted his head and looked back at the tub, using a bit of magic to bring a goblet size of water towards them, dropping it on the boys head. The boy blinked and looked surprised, he was drenched now. He looked at Izuku again, questioning his motives.


Izuku brought another goblet of water and dropped it over the boy's shoulders this time.


Red eyes never leaving him as he continued to do so, little bits of water splashing and hitting Izuku’s armor. He was washing away any dirt to get a better look at any injuries, they needed to be healed immediately, he didn’t need the human boy to get infections. He reached down and held onto the boy's wrist, even as he tried to pull away, Izuku didn’t let him. He healed the raw skin and the boy stopped struggling, his eyes wide as he looked down where they touched. Izuku easily got a hold of the other wrist and did the same.


His clawed hand trailed over the boy's ribs, a nasty bruise vanishing, over his cheek, a small cut disappearing. This was as far as he tested the waters, not wanting to push the boy any further, he didn’t need the human omega to panic on him over being touched too much. He stepped back and left, letting the servant demons deal with the more calmed slave.




Izuku learned the boy's name, asking an enchanted book of whatever he pleased to know.




Katsuki had no surname, as many slaves don’t. He did not ask the book anything more, he closed it and traced the intricate patterns on the cover. He was curious about this human, he had learned much about alphas and betas, omegas were a rarer gender. Even if they were in scriptures and books, the telling of them was that they were nymphomaniacs, sex-crazed beings. The symptoms similar to that of an Alpha’s rut, why was it different? Humans had their cycles much too often. Izuku experienced rut possibly once or twice every two years, he knew of other omega demons that would have similar cycles.


Human omegas had their heat every month regularly. Human alphas had their rut every two months. Even beta humans experienced weeks in the year where their fertility rates shot up, though that seemed much better than how the two other genders had it.


He knew humans lived much shorter lives but it seemed more of a hindrance than anything. He couldn’t imagine the anguish.


Izuku looked up, his chamber door opening and a fluffy headed Katsuki was ushered in. The slave boy’s previous clothing no longer in sight, the servants had dressed him in much more appropriate clothing. Instead of sheer skirts and shirt, he was dressed in black pants and a shirt that covered some of his chest. The demons green eyes fell towards the claiming collar the human boy still wore, something for the demon king to tear off and to find new skin to sink his teeth into.


The slave glaring at Izuku as soon as their eyes met. He thanked the servants, they gave the human boy a weary look and left. Izuku wanted for them to leave then turned back to his desk to think, he could hear the human slowly begin to pad around the room. Izuku could imagine what he was looking at, decorative weapons, the horns of a dragon planted on the wall, wings of beautiful fairies in glass displays. All collections for the hundreds of years Izuku had lived.


Izuku wanted to know what the human would do, almost wondered if the human would try and fight him. He had forgone his armor in his chambers, if the human managed to grab on his weapons that hung on the wall. Katsuki could scratch him if he tried hard enough. It would be entertaining, to say the least.


“What are you going to do with me?”  


Izuku turned his head towards the omega and raised an eyebrow, he had no reason to respond to the human boy. It would be much more interesting if the boy thought he couldn’t understand his primitive language. Katsuki glared at him, fists balled at his sides as Izuku kept the air of silence around him. Those red eyes were rather beautiful, if they were the eyes of an alpha, Izuku would hesitate to keep them in a jar for his collection.


“Answer me! I asked — What are you doing?” Katsuki took a step back as Izuku moved in an instant, standing in front of the omega, holding his chin up to look at the demon. “L-Let go!”


His voice cracked as he tried to pull away but being touched again by the demon made his body freeze up in fear and shock. Izuku knew he was double the threat for the boy, a demon and an alpha. Izuku’s head motioned to the bed and Katsuki followed his eyes, face flushing as he turned back to the demon, new fears emitting off him in waves of scent.


“You’re fucking crazy! I’m not getting into bed with you!”


Izuku sighed and rolled his eyes, he reached down and picked the boy up, placing the lean body over his shoulder and walking to the bed in long strides. Katsuki let out screams, kicking and bringing his fists down on Izuku’s back.


The demon king dropped the boy on the bed, watching him scramble to the other side of the bed, away from the demon, watching with wide eyes. Izuku pointed at the bed and walked back to his desk, sitting down and looking over his scriptures again.


“What…” Izuku heard Katsuki mumble from the bed, but he didn’t hear the bed creak or anymore shuffling to signify that the boy got off the bed.


Izuku would use magic to place books back on the shelves, bringing new books to look over. An hour passed and when he turned his head towards the bed, Katsuki was glaring at him, his legs from to his chest, his chin resting on his knees. But his eyes were heavy, his shoulders slumped and Izuku could almost smell how drowsy the omega was.


“Are you scared?”


Katsuki didn’t reply, how could he? He didn’t understand that demonic language. Izuku understood human language, though he was sure his dialect would be too strange for the human to understand. If he practiced when he was younger like his father wanted then maybe he’d communicate easily. Izuku said nothing else and went back to reading.




Izuku read on foods that were more beneficial to humans, Katsuki was rather thin, extremely so. The demon king decided if he was going to keep the human boy, might as well keep him nice and well-fed. It would be up to Katsuki to eat though, by the behavior the omega had kept, it didn’t look like he would be subservient to anyone, not even Izuku. Light began to glow in the room, it was dawn and Izuku had sat all night reading.


He looked over and was glad to see Katsuki still sleeping, the boy falling asleep against the pillows sometime in the night. Izuku had decided that he would make the most of this situation, learn of omega behaviors and their cycles from an omegas point of view. Books were useless, written by alphas who wrote a perverse and delusional version of omegas.


Izuku wanted to write books and educate other curious demons, wanted to fill his father’s journals on pieces of missing information.


The demon king made up his mind.


He would hold on and learn from this human boy for as long as he could.



Chapter Text


Keeping a human was proving more difficult than Izuku first anticipated, either it was humans in general or it was simply the lack of fear and the pits of hell attitude that Katsuki held onto. The way he spoke, the way he acted, it continuously fueled Izuku’s theory that Katsuki was newly captured when he encountered one of the Human Kings.


He spoke well enough, he could have been amongst the middle class of humans. Katsuki did not have one scar or blemish on his body from what Izuku deduced when he kept to the corner of the bathroom to watch servants clean the omega. Katsuki also had no scarred mating marks on the nape of his neck or his shoulders. The omega was in the beginnings of the most fertile years, meaning he could have been sheltered until a proper match came along.


Since Izuku was essentially keeping Katsuki as his pet–to observe and learn from and nothing more–would that mean Izuku would allow Katsuki to mate amongst other demons? Would he release Katsuki once he learned what he wanted? Izuku often pondered what he wanted to learn exactly, though what he knew indefinitely was that he knew close to nothing to omega human behavior.


He should soon set up teachers for Katsuki so that at least in his time in the Demon Kingdom he would become educated. Katsuki could go back to the human world far superior in intelligence than other humans.


Before Izuku could ask any of those questions of the human or start learning, he assumed getting their names to each other was the first step. It was a bit harder than Izuku thought it could be, his language translated his name strangely and had Katsuki scowling.


“Izuku.” Izuku felt an idiot as he pointed to himself, saying his name, his accent much too heavy, his words twisted as if in his language. Katsuki made a face and stared his red eyes into Izuku’s green, his mouth moving for a moment before any actual sound came out.


“Ku… D… Deku?”


“Izuku… Izuku.”




Izuku rubbed his forehead, he supposed, for now, it was close enough, while it didn’t suit him after hundreds of years being called King or Izuku. It was fine. This time, he pointed a clawed finger to the boy, the human's name rolling off his tongue in a way he could not describe.




“Hah? What’s that?” Katsuki frowned, crossing his arms over his chest, cheeks pink and Izuku tilted his head in question. The omega almost looked offended by the way his name was said, he seemed to have none of it. “It’s Katsuki, not whatever you just said!”


“Kac… chan?”


“Katsuki! I don’t know you, you don’t get to give me pet names!”


Izuku furrowed his brow, his claw scratching his glowing marked cheek and he swore he was saying it correctly, he repeated it in his head a few times before saying it out loud. Every time, he got it wrong, no matter how hard he tried. The two went back and forth until Katsuki threw his hands up in exasperation.


“Wait… I swear I’m saying it right? Katsuki… Katsuki…” Izuku tried again, his fingers pinching his bottom lip in thought, every time, Katsuki seemed to turn pinker and pinker, eyes glaring daggers at the demon. “Kacchan.”


“Fine! Call me whatever you want, Deku!” Katsuki turned, waving his hand at the demon, he doubted the demon even understood most of what he was saying anyway.


Izuku would have to figure a way around this without bothering his translator, Shouto already crossing his arms and scowling that he would not translate to Izuku’s omega. Though, the Demon King couldn’t say the title didn’t sit well with him, warmth on the back of his neck making him question himself.


Katsuki also proved to be just as curious in his own way, his eyes never left Izuku when they went out and about. At first, the king believed that the omega was just observing his behavior, making sure that Izuku kept his distance for the time being. But, Katsuki’s mouth would open slightly when Izuku performed magic or did regular things in his day, things that Katsuki would never see in the human world. His eyes were learning, watching everything, memorizing everything Izuku did.


The demon king had caught him trying to use his book of secrets, a book that revealed whatever the user asked within reason. Magic had to be inputted from the user and Katsuki as a normal human, could not use magic unless taught. Izuku could see with his demon eyes a beautiful cauldron of magic within the omega, he was sure with practice and lessons under the right teachers. Katsuki could become as powerful as some of the demons in the castle.


“What the hell? He did this.. and opened it… Why isn’t it working!” Katsuki grumbled, opening the book of many pages, wondering if it was a certain page. The book on one of Izuku’s tables, the omega saw it often and Izuku would speak to it. The book speaking back or making words appear in visuals of fire or ice.


“Kacchan?” Izuku asked, a grin on his face, though covered behind his clawed hand. He didn’t need the boy to throw a blushing tantrum trying to hide the fact he was snooping.


“Hyah! What are you! What are you doing sneaking up on me!” Katsuki shut the book behind him, turning around and trying to hide the book behind his lithe body. Katsuki glared at him with such ferocity that Izuku could almost imagine the little horns and wings on the omega.


“Little omegas shouldn’t be too curious.”  


Katsuki assessed the word omega and narrowed his eyes at the alpha, taking a step aside for Izuku to place his palm inches above the book. The pages flapping widely before stopping. Izuku looked at Katsuki expectantly, motion to the book with a little tilt of his head. The human boy blinked before jumping slightly and looking at the book.


“Tell Deku… He shouldn’t sneak up on me or else.”


The book crackled and began to speak, almost a feminine voice. Katsuki assumed repeating the words in that demonic tongue. Izuku blinked, his chuckle low and he began to laugh. The marks on his cheeks glowing the louder he laughed, Katsuki just watched, almost shocked to see a demon look so joyous over being scolded.


“Kacchan, sow—Sorry.” Izuku corrected himself, his eyes closed with such from his laughter, the book in front of them flipping shut. Izuku’s laughter died down, a jostling chuckle as the Demon King went to do other things around his chambers. His coat lifting over and off his body with a flick of Izuku’s wrist, exposing broad shoulders, black wings extending after being folded all day and his long, thick tail swaying calmly side to side.


Katsuki felt his heart skip a beat.


He licked his lips and looked back down at the book, he’d have to figure it out sooner or later.




The Demon King sat in his study, completely and utterly betrayed. In front of him, a most disgraceful display.


His two very own hellhounds, the same two he summoned as a child, the same two he had fed countless lives and had chase down victims to bite at their ankles, their only goal was to kill and to serve. Vicious summons, the evilest of all summoning creatures. Creatures that have prowled the earth and fed on the remains of any living being to satisfy their bottomless pit of savage hunger. His two hellhounds had betrayed him for the first and last time of their meek existences.


The two creatures curled up around the human boy as if Katsuki was their master or their savior. One hell hound, Scelia, had her head in Katsuki’s lap. Her fiery tail wagging like if she was some earthly mutt as the boy's hand caressed behind her curly horns. The other hound, Iythe, had her paws crossed under her head as she slept over the omega’s knees, ears flopped in complete ease.


It had begun not too long after Katsuki began following Izuku around, it was obvious he would meet his longest-standing summons at one point in time or another. The Demon King rememberers how Katsuki just froze up as the two hounds surrounded him, walking around him in circles, sniffing at him, their noses digging into his stomach or his palm. Izuku had never seen them act affectionate with anyone other than himself, so it came to a surprise when Iythe let her tongue fall out of her mouth as she panted. Standing on her haunches and knocking the boy over, Katsuki had let out a scream of shock but it quickly died down when both hounds began licking at him, their tails wagging wildly.


“You like that, what about here? Here?”


Izuku watched Katsuki look completely enamored with Scelia, his hand running over her furry scalp. For a human, he didn’t act as if he was within the forest full of demons. The boy watching her reactions when he scratched at a good stop, her split tongue hanging from her mouth as he reached under her skulled chin.


“Oh, that’s the spot.” Katsuki chuckled, the smile on his face truly bringing forth how young the boy was. Between his childish play with the creatures to how he laughed when Scelia jumped to lick at his cheek and chin.


“Scelia.” The hound lead her attention to her master, her snout pointed up at him, Katsuki’s light chuckle disrupted her attention. Her tongue finding its way back at his cheek.


“Scelia? What’s that? Is that your name?” Katsuki asked her quietly, her snout poking into his palm, tail flapping ferociously back and forth.


Izuku left ignored as he stood surrounded by floating books and journals, he turned his attention to the book that wandered in front of him. His eyes running over the words quickly before sighing, the book slapping shut and shooting off to be placed where it belonged. He was looking to see if there was a spell that was safe for humans, a spell that would allow Katsuki to communicate with the other demons of the kingdom.


It had been almost been one full moon cycle since Katsuki came into Izuku’s possession. The question of when the omega would heat would often cross Izuku’s mind. The blond was still overly cautious when he came to be around the Demon King. Izuku could see why. He was an alpha and Katsuki was an omega, usually the genders as such didn’t interact unless it was family or to possibly mate. Though Izuku had no real urge to hump the human boy, he could easily admit how breathtaking the omega was once he was well fed and healed of any injuries. Izuku was sure if Katsuki was a demon or if he were human, then their paths could have crossed in the ritual of mating.


Katsuki slept in Izuku’s bed, only after making sure that the demon would not crawl into the bed as soon as his eyes grew heavy. Izuku had thought of giving the boy a chamber but being an unmated omega posed a few problems for the demon king. Even with guards, demons could figure out how to get to the boy. Under the king's hand or not, demons were just as beasts of alphas as humans. A lingering thought of Katsuki’s heat crossed Izuku’s mind, what would be done in that situation but it would be better left when it happened.


The boy followed Izuku around, muttering whatever came to his mind out loud in his human tongue. The demon king found it amusing, most of those who lived in the castle didn’t understand human speak anyways. Only Izuku, Shouto and a few of the elder council members. The omega only eating things that Izuku put on his plate, eyeing the cooks suspiciously. The first few days he wouldn’t eat until Izuku took a bite first, almost then force-feeding Katsuki. He couldn’t have the subject of his curiosity starving to death.


It really couldn’t be any other way, Katsuki just didn’t trust any of the other demons, he had a speck of dust compared to the trust he had in Izuku. Trailing after him, watching his perform magic and speak that demon language with others. The Demon King could tell the human boy was intently listening, as if he would suddenly decipher their language and understand every word said.


“I do not think the human child should be here for this peculiar council meeting… With all due respect.”


Izuku hummed and looked down at the table before them, a layout of his land, little figures moving along the edges. They watched a large group of humans wander an edge of the vast forest before they stopped moving.


“The boy can not understand us if it makes you uncomfortable—you may leave, Commander.”


The old demon grumbled but did not protest or move from his place. A passing thought in the king’s mind, maybe he should replace the old demon. As much respect he had for the older council member, it faded with every day. His father long was gone, the previous king’s council should also be gone. The council should be filled with a handful of demons that Izuku trusted and could easily confide in.


Izuku’s eyes trailed over to wear Katsuki sat, lounging in Izuku’s throne as if it was a simple chair. The omega dressed in blacks and reds, the colors making his pale hair almost like the sun in the room of dark demons and darker magic. The collar resting on the base of his neck, a different leather with an embedded jewel to let Izuku know his whereabouts. For precautionary purposes, of course. Scelia and Iythe at his feet, growling and snapping at the feet of demons who stepped too close to the omega. The demon king figured this was better than guarding the boy himself, Katsuki even encouraging it by petting their heads and speaking to them words of encouragement in a low voice.


Izuku’s eyes simmer with pride, the human’s unusual red eyes glaring the demons in the rooms. Glaring as if they were nothing more than lowly creatures, livestock even. Though, when his eyes met with Izuku’s, they trailed down, looking at the hound in his lap. Fingers tickling down her horns.

The Demon King turns his attention back to the large glowing table, the indicator of humans had yet to move.


“They’re setting camp, by the looks of it, kero.” An alpha woman commented, Izuku’s eyes trail to her, a new addition to his council. Tsuyu Asui, a demon priestess with the features of a frog, the tip of her tongue hanging from her lips as she placed a finger at her chin. “Should I send a three-eyed crow? Some rumor toads?”


Izuku looked to the region the humans resided. “Send toads, they reside in the wetlands, a few of your creatures shouldn’t bring forth suspicions.”


“A few? I was thinking thousands, kero…” Her chaotic smile made Izuku chuckle and he shook his head.


“I’m sure a handful will give us the same details, Priestess.”


Tsuyu hummed a small incantation, a small portal opening near where the human spots where. Her hands went over the portal, her hand glowing green. Izuku turned his head, Katsuki watching with wide eyes at the magic the priestess performed. Tsuyu continued her spell and that’s when the omega first saw it.


A toad. Slipping out of her palm, wet and slippery. It fell through the portal, then another and another. Katsuki counted seven toads in total, her incantation ending and she closed her palm—the portal shutting with a strange sound, almost like hissing and crackling from firewood. Katsuki watched Izuku hold his hand out to the woman, her finger tracing in his palm and they pulled apart.


“You have control of my toads, King.”


Izuku nodded and held his hand out, another portal, though it was different. As if they could see what the roads saw, Izuku’s hand moving to guide any of the toads in a certain direction.


“You’ll have to teach me this, it’s very interesting to see through the eyes of others summons.”


Tsuyu just giggled and touched her cheek, nodding her head at her king. “It is my mates' magic, I’m sure he would eagerly show you.”


“Ah, well, he just had a child, did he not? I can not bother a new mother when he is this busy…” Izuku voice dropped to a murmur and then tilted his head, his attention focused completely on the visions. Easily over a thousand soldiers setting up camp, laughing and drinking as if they weren’t under the watch of the demon king. Izuku looked down, his fingers pinching down where the soldiers were, then he spread. Their figures becoming more clear, the information of the toads running through their camps giving him insight on what he was dealing with.


“They’re rather brave.” Another demon commented, Izuku nodding and humming in thought. From the toad's vision, he saw a few begin to wander into the first trees of his forest. He had to admit, it angered him a bit.


“I wonder exactly how brave they will be...” The Demon king walked over to where Katsuki sat, the omega sitting up straighter as the alpha stood in front of him. Looking down at the boy, a moment passed before his eyes then looked to his hounds.


Katsuki’s hand froze on the hound’s head. “What are you-“


“Scelia, Iythe, lunchtime.”


The hounds eagerly left Katsuki, shaking their bodies to release themselves of any laziness and drowsiness. Their favorite person shifting from the human boy back to their original master.


Izuku opened a large portal, the edge of his forest in sight, with only a simple opening of his hand, the hounds growling in hunger. Katsuki could see their bodies growing, becoming more monstrous, more hellish. They were nothing like a moment ago, simply looking like large dog creatures with horns. Now their backs hunched, canines longer than fingers, muscles protruding over their bodies. Izuku pet both their heads, his hands glowed as he transferred a bit of power into them. Green lighting their bodies like electricity. He pulled away, whispering things that Katsuki could not hear and they bolted through the portal, fast as lightning.


Katsuki couldn’t understand why Izuku would turn the beasts that had been his only real friends during his time in the Demon Kingdom. He wanted an explanation but how could he ask for it without knowing what he was even feeling.


Izuku closed the portal, his hand reached out to Katsuki, urging the omega to take it. The boy eyed it the clawed hand in front of him. His hand raised and took it. His fingers barely grasped against Izuku’s. Katsuki pulled himself into a standing position and let himself be lead to the large table alongside the councilmen.


“Watch… Scelia and Iythe.” The first words that Katsuki has to understand all day from Izuku, his red eyes going from the demon holding his hand as if he were frail. He could see Scelia through the eyes of Iythe, her prowl slow and patient, drool dripping in abundance from the corner of her mouth.


Then Katsuki’s eyes landed on the first human soldier. Both hounds raced for the kill, bumping into each other, pushing each other. Iythe reached first, the omega didn’t flinch at the reading of flesh and bone, at the screams of the human that rang within the walls of the council room.


Katsuki could say without a doubt, he felt no pity for the human who was torn apart by the vicious hounds. He felt no pity as he watched another and another, soldiers running by the dozens out of the forest. Scelia and Iythe guarding the edge of the forest line, daring another to become their next meal. His eyes trailed back up to the demon holding his hand, the demon who was watching him instead of the hounds.


The demon who had a fond look on his face as Katsuki showed no sympathy for those of his own race, for those who sided with the humans. Izuku offered him a small smile, Katsuki’s fingers squeezed by the demon, ever so gently, heat flowing through his hand to his chest.


Katsuki felt his heart skip a beat. This time making him avert his eyes, he rather stare at the hound's feast on their successful kills than the face of the handsome Demon King.



Chapter Text



Izuku could smell it, Katsuki’s usually gentle scent now exceedingly sweet, wafting around in his study. Thicker than a Banshee's fur, heavier than a mother dragon. It shrouded all around him and he was sure if he were a lower demon, he would have jumped the boy the moment he was allowed.


Izuku’s green irises looked over where the boy was cuddled up with his hounds, all three of them asleep, Katsuki wrapped in a small blanket, his cheek pressed against his own shoulder. Peaceful in contrast to the thunderstorm and whirlwind of thoughts the Demon King was plagued with.


It is what he deserved for putting off the issue of heat until it surfaced.


Izuku let the books around him shut and drift down to the table, he walked over to the sleeping trio and knelt in front of them. Scelia opening an eye to look at her master, she shuffled closer to wrap herself around Katsuki and continued sleeping. He reached a handout, pushing the omegas fringe from his pale face. The heat radiating off the boy was stronger than usual, much hotter, every minute coming closer to the boy's cycle. Izuku hummed and stood, walking back to his table, a book on omega heat cycles in front of him.


Katsuki was closer to seventeen years old, about a year or two older than Izuku’s initial guess. An entire moon cycle had officially passed, it was normal for the omega to start heating eventually. His eyes read over the pages until he got to the information he desires.


“Anywhere between a day to an entire week… Seems tedious… Maybe a charm or a spell?” Izuku flipped the next page, two full-body diagrams of omegas. One male, one female. The differences weren’t many, aside from the male organ and the extra breast tissue. Both illustrations were similar. Izuku tilted his head, his eyes narrowing at the pages. He hadn’t given it much thought or even looked too closely but….


Now that he thought about it.


Katsuki had these parts, did he not? Izuku only watched to make sure Katsuki was calm and that the servants wouldn’t let their hands venture perversely. He did not gain much from the whole experience, most of the cleaning of the omega took within a bathtub anyways. Izuku had seen Katsuki’s flaccid male organ, as strange as human penises looked, Katsuki’s seemed normal in that regard. Izuku hadn’t gotten a view of the omega’s actual reproductive parts, but he was sure if he tried the omega would scream, flail or might even cry. Though Katsuki’s chest wasn’t as flat as other males, while it wasn’t impressive like that of other female humans. It was still impressive in regards of male omegas, enough that it would suffice in feeding any offspring.


His chest was mostly hidden behind the confines of the clothes that Izuku had tailored specifically just for him.


Izuku licked over lips, thinking of the omega’s heat made him fall deep into thought.


Would Izuku be the one to relieve Katsuki of the pains that came along with being unmated? Izuku knew enough that omegan heats lasted longer and were intolerable without a proper mate. The thought in itself angered him, most omegas presented around 14 years of age. Most omegas were given to alphas older than them to mate and to keep.


Izuku would not be the one to relieve Katsuki. He would not be the one to break the omegas trust by getting into bed with the boy. He had told himself again and again, after seeing the boy smile and seeing him laugh with the hounds. Katsuki was a beautiful creature, though, Izuku couldn’t see himself touching the boy in such ways just yet.


Izuku wanted Katsuki to freely choose a mate, even if it seemed cruel. He felt as if Katsuki could spare to wait a couple of years before spending the rest of his life with a dominant alpha.




Katsuki woke up to the hounds leaving him. He rubbed his eyes and slowly stood from his makeshift nap space on the floor. He dusted his pants off and walked over to where Izuku stood, surrounded by books like always.


The omega peered at one of the books that passed him, taking it in his hands to keep it from leaving. His eyes looked over the foreign language, looking almost like scribbles. He flipped page after page, little illustrations catching his eyes, looking doodles and the such. He turned the next page, a diagram of two omegas.


Katsuki felt his face catch fire at the extremely detailed drawing of the omegan body, his fingers letting the book go, it continued its floating passage. He dared look at the alpha who was entranced in a certain book, clawed hand at his chin as he thought deeply.


“Kacchan,” Izuku’s velvet voice disrupted his stare and Katsuki felt his back straighten as the aloha regarded him. The demon let the book in his hands go, the bound pages floating nearby as Izuku turned to the human. “Kacchan’s heat…. Soon.”


“Wh-What…” Katsuki took a step away, he eyed the demon suspiciously. A hundred thoughts running through his mind, why was Izuku interested in omega anatomy, why was he pointing out that his heat would soon arrive.


Unless… Izuku was going to be joining him for his heat…


“No, it’s not!”


An idiotic lie, they both knew it but Izuku still tilted his head, brows furrowed in question.


“Kacchan’s heat… Heat in two moons.” Izuku stated, it was a fact but the accuracy did not unwind the knot of nerves that found a home in Katsuki’s stomach.


“I told you, I’m not getting into bed with you!”


Izuku furrowed his brow, shaking his head.


“Kacchan,” he pointed a clawed finger to the boy. “By himself.”


Katsuki scowled and eyed the demon, from the base of his horns to the green scales on the base of his thick neck. He wasn’t sure was game or trick this was, but if Izuku tried anything, he would go kicking and screaming.


The demon said nothing more and a book fell into his clawed hands, his eyes peering over the open pages. Katsuki licked his lips and balled his hands into fists, returning to where he napped. He had little in mind of what to expect but so far, Izuku hadn’t betrayed him or made Katsuki lose trust in him yet. He could only hope his words held their promise when his heat began.




Katsuki hugged one of Izuku’s pillows close, his heat was starting but he was tired, riddled with worry. Izuku had come into the room moments ago, standing at his desk, book in hand like always. The omega watched him, if he took a step closer to the bed, the way the demon's feet shuffled as he moved around the area of his desk, how his wrists flicked to bring himself more reading material.


“You’re not going to… Try to jump me, right?” Katsuki grumbled and he ignored the warm spike of fondness that spread through his chest when Izuku glanced at him. His eyes glowing green in the candlelight room, his twisted horns catching gleam and Katsuki doesn’t know if he’s intimidated or attracted to the demon at that moment.


“No, Kacchan by himself.” Izuku’s broken human tongue was charming in Katsuki’s weak and vulnerable time. The omega licked his lips and buried his nose into the pillow, the scent of it always threw him off. He had taken almost permanent residence on the Alpha’s bed, when had Izuku had time to still keep his scent so prominent?


Katsuki lost in his thoughts for a moment that he hadn’t noticed Izuku at the edge of the bed until the demon sat down, his weight causing the bed to sink and Katsuki’s body to lean towards him. His breathing took a hitch, heart race booming in his chest and he could feel the thrum of it in his ears. Izuku reaches forward and his red eyes shut tightly as he awaited the touch.


“Kacchan… Sleep.”


Katsuki blinked his eyes and looked up, Izuku hand touching—more so petting—his head. Flawed fingers threading through his blond hair, soft scratches at his head and Katsuki watched Izuku’s mouth turn and twist. Demon tongue flowing out of the man’s mouth so eloquently and flawlessly, Katsuki could see a soft glow coming from above his brow.


His eyes grew heavy and Izuku smiled, no malice, just soft and fond. Katsuki was almost reminded of how his mother used to smile at him, how she would be gentle at times of his heat, how she protected him.


He fell asleep almost an instant after the spell was complete, Izuku laying him down and pulling the covers over him.


The demon stood and one of his journals came over, a feathered pen scribbling his thoughts down as he walked back to his desk.


“It seems to have worked, I’ll just have to see how his appetite and fatigue will be he wakes up…” Izuku licked over his sharp fangs and crossed his arms over his chest, heavy tail swaying from side to side as he thought. He glanced back to the sleeping human in his bed, the heavy scent of heat slowly diminishing as time went on. The demon nodded to himself and felt almost accomplished over a simple sleeping spell.


Now, to see what teachers would supplement Katsuki’s mind and soul. He supposed he should almost get combat trainers, the omega should be able to defend himself even against the most vicious of other humans. He had an idea for Katsuki’s lesson plans, human history as well as demon history, the common tongue as well as demon tongue. Combat and self-defense now making its way into that list.


Izuku licked his lips and tasted poison, his teeth and jaw ached, as much as he tried to deny it, he was still an alpha with an innocent and unmated omega in his bed, only the sheets between what his body wants. His eyes can see the unmarked skin of Katsuki’s neck, the omega open for the taking. Ready to have Izuku’s teeth sunk into his flesh, to become the demon king’s forever. 


The demon slams his books down on the table, his thoughts broken when Katsuki shifts to get comfortable even in his sleep. Izuku left the room in a hurry for fresh air.




Katsuki’s body woke before he truly did, his eyes closed still as he buried his face in the pillow. The hard, hot-


The omega shot up, his cheeks in flames as Izuku looks beyond peaceful against the sheets, he’s shirtless but the thrown about sheets show his tied pants. Katsuki’s hands fly to his own body, his clothes still in tack, a little wrinkled but all in place. It’s almost a relief but that still didn’t explain why the demon was in bed with him.


“Deku.” Katsuki swats at Izuku’s chest, the man letting out a heavy breath, his eyes nearly black as they open to look at his bed companion.


“Kacchan… Good morning…” Izuku sits up, his hand coming up to rub at the base of his horns then down to scratch at his pointed ears. Katsuki eyes him, the first time since arriving that he hasn’t seen the demon king look regal and sophisticated. Even now, hair messy, eyes swollen with sleep, marks on his arms from laying in the same position; Katsuki found his horribly handsome and that infuriated him to no extent. The omega raised his hand and slapped the demon, rushing to get off the bed in a panicked shuffle of tearing the sheets off his tangled legs.


“What do you think you’re doing!?” Katsuki accused, his fists clenched in front of him. Izuku blinked and while the human’s slap across his cheek and the corner of his mouth didn’t hurt or even sting—it surprised him and he couldn’t make much sense of the warm pit in his stomach.


“Sleeping,” Izuku rubbed his jaw, then pointed at the bed. “My bed.”


“I! You’re!” Katsuki started his sentences but he couldn’t find an actual reason to keep arguing, he was only frustrated by finding the demon attractive to some extent. He pinched the bridge of his nose and pouted, mumbling out an apology that Izuku waved off as he too got off the bed.


“Hungry? Feeling well?” Izuku asked, his black wings stretching and expanding to their full before laying soundly against his back. He walked over to Katsuki, a journal immediately hovering near the pair as Izuku took Katsuki’s chin in his hand. The omega looking at him like he had lost his mind.


“I’m fine? Fuck are you touching me for?” Katsuki asked, his hand brushing against Izuku’s as he took a step back.


“Kacchan slept through heat,” Izuku explained, his pen writing away without being touched, he was mumbling in that pesky language again and the pen seemed to keep up. Katsuki quickly got the gist of it, a small memory before falling asleep coming back to mind. This hadn’t been the first time that Izuku had studied him so blatantly. “Speaks well, no movement delay, overly energized it seems…”


“Quit mumbling, Deku…”


“Mm, hungry? Slept for three days.”


“Three?!” Katsuki blinked and furrowed his brow, so his hunches were right. While he had post-heat cramps in his stomach from hunger, he had no other major symptoms. No soreness in his body, no extreme fatigue. Hunger was expected, he slept for days it seems. “How?”


“Magic, Kacchan.”


“Magic, magic, magic…” The omega mimicked him, mocked his words and Izuku was amused for a moment, his pen stopping its writing as he watched the humans face then and twist with every tease. “When are you going to show me how to use that magic, huh?”


“I won’t. Teachers will.”


Katsuki’s eyes were firm on the wide grin on Izuku’s face, how white his teeth—his fangs—were, how the red and green marks on his cheeks stretched from joy.


“They’ll teach magic after Kacchan eats.”




The demoness assigned to Katsuki was named Midnight, Demon of Lust. She was beautiful but something about the way she draped over Izuku left a bitter taste on his tongue, it disappeared almost instantaneously when she hugged the human to her impressive chest, Katsuki’s ear could hear her multiple heartbeats, strong and powerful.


“Aren’t you a darling!” Midnight pulled him away from her chest, her sharp claws holding his cheeks as her strange three eyes looked at his face. He focused on the eye on her forehead, blinking and almost like a jewel by the way it twinkled. She spoke so well and clearly, if it weren’t for her demonic markings and wiggly, thin tail, she would have seemed like the most beautiful human woman. Now, if only Izuku could communicate this well. “And a beauty! Look at those eyes, you don’t see that on humans too often!”




“I’m going to have so much fun teaching you! You’ll get to know your body like no other…” She blew air into Katsuki’s ear, he covered his ear with a slap of his palm and pushed her away, his face flushed pink. His eyes turned to the demon king, that same grin as the man wiggled his fingers goodbye and left the room. He stumbled over his own feet, landing on his ass.


Midnight placed her hands on her knees, a devilish and teasing look on her beautiful features. She looked like she was looking down on a poor little animal that she was going to make a feast of.


“I-I’m not sure if this is-!”


“Now, now!” Midnight smiled, she pulled something like a horsewhip from the belt of her tight pants. She straightened up. The straps whipped against her palm and suddenly Katsuki was reminded he was in the Demon Kingdom, his position as the Demon King’s pet had no status in this room. “Let’s start with Human History, boy! Let’s learn all about those pesky beings!”




“Have fun?”


Katsuki was exhausted really, his morning and afternoon preoccupied with all sorts of characters. A loudmouth who began teaching him the basics of Demon Tongue. Midnight who almost beat Human History into him all morning. And one more strange demon, a drowsy man with black hair, Katsuki’s current favorite only due to the reason that that man, Aizawa, was the most tolerable out of the three.


Aizawa began by making him draw all sorts from circles and shapes, summoning templates. Katsuki’s hand aching by the time Izuku popped his head in to rescue the poor human. His hounds eagerly crowding Katsuki and licking at his hands to persuade him to pet their furry heads. He couldn’t take a step without bumping into one of them or one of them, Scelia, stepping on his feet from how close she was.


“It was… Annoying.” Katsuki answered, his hands coming up rubbed his cheeks, they still stung after Midnight had tugged on them so much. He looked around, a corridor he hadn’t seen yet. They came to an open area, purple grass and a little fountain spewing crystal pink water. He looked around and scowled. “What is this?”


He turned to Izuku and felt his breath hitch as the demon removed his coat, a thin shirt underneath that did nothing to hide the muscles of a prime alpha. His large hand raised and touched his horns with a glowing touch, the thick bones disappearing before Katsuki’s eyes. His large leathered wings, his heavy spiked tail; both gone with just a touch of a finger. Izuku soon standing in front of Katsuki, almost appearing to be human in front of him, even in this form, he was no less attractive. His eyes trailed over the more obvious display of freckles along Izuku’s nose and cheeks, other demonic markings having hidden them for the most part  


Katsuki was beginning to think it was starting to gear away from appearances at this point…


His attention snapped up when Izuku began speaking, a small smile on his features.


“I’m Kacchan’s combat teacher.”


Katsuki swallowed and nodded stupidly, his head turning away—eyes focused on the little pouring waterfall.


Izuku was teaching him, that was all and nothing more at that moment. He had to learn, whatever the demon king had just said to him.


He really needed to stop thinking of his captor—his rescuer?—like this, he had to find one way or another to ignore the aching pain of desire in his stomach and the aching racing of his heart in his chest.


“Guard yourself.”


Katsuki's eyes went wide when Izuku clenched his fist and brought it to Katsuki’s shoulder, it hardly hurt but caught him off balance. He stumbled a couple of steps back and tried to plant his feet as Izuku easily closed the distance with one stride. He was hit, no, pushed again and this time brought his arms up, Izuku’s fist coming in contact with his forearm. His body moved by the force but he didn’t stumble.


Again and again, Izuku smile growing wider and wider by the second and Katsuki would have thought the demon to be toying with him. It was no secret the power difference between the two, Izuku could easily overpower him or even kill him with a mere hand.


Katsuki trying his best to block every shove, they were slow and easygoing to the demon but to a human who hadn’t experienced combat? A horrible game.


“Spread your feet.”


“Protect chest and stomach.”


Little pointers and slowly, Katsuki found himself standing strong even when shoved harshly. He wasn’t sure where to keep his eyes yet but he was sure to learn.


“Good.” Izuku nodded to himself, a hand on his chin as he muttered something that Katsuki had yet to learn in his lessons. The demon turned and began to walk to one of the walls with a small armory. Katsuki’s nose scrunched up in a scowl and he glares at Izuku 's back. “Sword or staff?”


Red eyes blinked at the two weapons that were presented to him, a grin on his boyish face.




He was met with an equally eager grin.


“Good, Kacchan.”



Chapter Text





The human said nothing. He walked slowly around the dark dungeon room with the scent of the Demon King surrounding him, laid over him like a blanket. He stepped around, the lesson was to expose Izuku with a spell, his own vision stolen by the demon. 


“Do you remember your studies?” The voice draped over him, making him angry, making his body heat up—it was better, the more sweat produced, the better his grip was on the magic.


“Do I look like a slacker?” 


An amused chuckle bounced off the walls, almost as if right over his head. He didn’t flinch as breath fanned over his ear, a clawed hand on his dancing along his waist. Katsuki turned, a quick incantation from his lips caused sparks to crackle at his palms and then a loud, ringing explosion. He hit nothing underneath his palm. 


“You have not caught me… Kacchan, do you need help?” Izuku’s voice all over the room again, the gentle sound almost condescending. The demon always had some way of being worried, even after toying with Katsuki for what seemed like hours on end. The human heard a step behind them, another in front of him, he couldn’t rely on noises alone. 


“Come out and I’ll show you who needs help!” Katsuki’s tongue twisted and his lips formed in ways most humans couldn’t, his demon speech almost on par with other demons. The moment his lessons had begun, nearly two years ago, he would not miss the chance to efficiently listen to every detail during Izuku’s council meetings. 


His breath hitched as his vision returned with a snap of fingers, Izuku bent at the waist to be eye to eye right in front of him. 


“Who needs help?” 


Katsuki pushed his palm against the demons cheek and got him out of his personal space, he didn’t need to get flustered before getting to his other lessons. Midnight would not cease her teasing if she even caught a whiff of a shy scent. 


“Shut up.” 


Izuku let out a huffed laugh, crowding Katsuki again for the sole purpose of how he liked the way the omega smelled when beyond embarrassed. Almost like a kitten, prissy but loving of attention. 


“Your speech has improved again, you respond proficiently.” Izuku complimented, tilting his head side to side, little snaps of pressure making his sigh softly. Katsuki eyed him and licked his lips. They dressed themselves in their coats and Katsuki making sure his collar was secured around his neck. Izuku’s tongue licking over the top row of teeth and fangs, poison a common taste in his mouth as he let himself gaze on the omega’s soft flesh. Katsuki made the first move to leave the room and Izuku followed closely behind, his eyes wandering from the human's neck down to his supple backside. 


Now for the rest of their busy days. 




Almost two years since Izuku began caring for him. Within that time, his magic was parallel to other demons—Aizawa teaching him that omegas, in general, were more in tune with the earth, where magic was drawn from. His favorite spell was the one that let him cause destruction from the palms of his hands, only to contradict Izuku for suggesting Katsuki pick something from an element of water or light. The Demon King had created a little demon out of a human, magic spells cast wildly when learning, demonic speech used in obscene ways of cursing. Katsuki has gained confidence extremely quickly, never holding his tongue—Izuku often pretending to not hear the loud human as some of his council became insulted. 


He was amused, after all. 


Not much had changed—Izuku still studied Katsuki vigorously, his eyes watching as the human would scent things when he taught no one was looking. The way he purred when he rubbed his face into the strongest scented of Izuku’s pillows. The way he flushed around other omegas but scowled and glared at alphas who dared to look in his direction. Katsuki acted within some of the parameters of omega behavior, heats, scenting, obvious displays and scents of attraction. 


Izuku was no fool, very early on did Katsuki have this peculiar scent towards the demon. 


Hot, smoldering, wet.


 Izuku wanted to bury his nose in the omegas skin and taste at where the scent emitted from, he was sure he would never tire of it. Even so, he was sure this was a mistaken case, Katsuki only felt this way in light that Izuku was providing for him. The demon was sure if Katsuki was allowed more humans, more alphas, the emotions and desire would shift to any one of them. 


Katsuki was young and overwhelmingly inexperienced in the world of mating, Izuku felt cruel at even the thought of taking the omega for himself. 


Though, it seemed his council had caught onto his dilemma, adding salt to his injuries every meeting. 


“My king, it is about that time again, is it not? Season of coupling?” 


Katsuki’s red eyes kept down on light board watching little images of soldiers setting up camp near Izuku’s forest. When the king cleared his throat to rid himself of bile, the human peered at him. 


“This may not be the most appropriate-“


“Why not? Your father was much younger than you when he married—think of the kingdom.” 


Izuku narrowed his eyes at the blond demon, Toshinori was an older demon, someone who advised him, gave him comfort after he rose to the throne. Toshinori smiled, it was all in the best interest. Izuku was a few hundred years old, his relationship with studies and learning to keep him from seeking anything more serious than a rut partner or a companion for his bed. 


Since Katsuki’s arrival, Izuku had been dry, not mating, no sexual desire for others. The Demon King has one rut during this time, the entire time fucking into magic flesh, growls of Katsuki’s name were loud and the images in Izuku’s mind made him still feel perverse. 


Izuku could see Katsuki watching at him through the corner of his eye, strange for the blond to remain silent. 


“I don’t need a mate, marriage is for weaker beings.” Izuku ended the conversation, hopefully, this would give Katsuki incentive to begin expanding his search for a mate elsewhere. 


“Possibly not marriage, an heir?” 


Izuku felt his loins stir as Katsuki’s hands began to fiddle amongst themselves, quite a skittish and nervous habit he never rid himself of even as an adult now. The human was listening, this time, obviously staring. Izuku looks down at the small human. 


He could mate with anyone, he was the king of demons, ruler of the Forest of Mysteries. Any heir that was born from his seed would be far above any other demon in terms of power and skill. Shouto, for example, was equally strong as other demons despite being half-human. 


Izuku was not sure if he would ever live out the guilt of having Katsuki fat with an heir, forced to care for a child rather than living out a life outside of omega instinct. 


Hid eyed stayed locked with Katsuki’s. “I don’t need an heir, I don’t need a mate.” 


A lie that hurt his soul, the one he wanted to mate in front of him, eager and willing. 


Katsuki turned, his eyes downcasted on the magic table, a scowl forming in his face. 


The matter was dropped and Toshinori looked apologetic, Izuku shook his head and let another council member bring up the subject of the soldiers once again. Whatever it took to take his mind off having an heir, about mating, about Katsuki. 




Midnight held a book in her hand, Katsuki reciting the names of current Kings and the name of their kingdoms. Though, when he made a mistake, he paused longer than usual and after a moment seemed absent-minded. 


“What’s ales your mind, kitten?” Midnight quipped, her three-eyed glittering with the prospect of gossip. If there was a rumor in the castle, she wanted every detail of what or who was involved. 


“I got rejected before I could do anything about it.” He sounded angry almost, punishment himself for something that was out of his control. “Idiot Deku…” 


“Ooh?” Midnight sat in Katsuki’s table, her long legs crossed and she leaned in close. “Well, you are young.” 


Katsuki flinched at that. 


“And a brat.” 


Another flinch, that one stung a bit. 


“Inexperienced, a human. Besides, why would a King want to be tied down to one omega when he could have hundreds?” 


Katsuki glared at her, he knew all these things, constantly reminded by unavoidable beings in the castle. Omegas boasting often of how passionate the king was, how giving he was—even during his past ruts—the way Izuku was sweet with those who had been his rut mates. Katsuki barely had gotten to experience heat during his time in the castle, Izuku always making sure to put him to sleep to avoid suffering or pain. 


“But, King Izuku is an idiot… It’s obvious the way he looks at you, maybe he’s waiting until you are older? I’m surprised you weren’t marked and pupped during your first night with him.” She smirked at her phrasing, Katsuki skin blazing red at the implications. 


“He barely even slept when I stayed in his room…” 


Midnight raised her brows and then a coy smile filled her plush lips, cocked with mischief. 


“Maybe, you need to use that omega charm of yours.” 


“My fucking what?” Katsuki almost looked offended, like if she was insulting him. She rolled her eyes at his dramatic face, her hands touching his chest and then his waist. 


“This! Alphas go wild at a little flirting, wear revealing clothes!” Her long nail trailed up to his black leathered collar, her finger slipping right under it. “Remove this… Show him mating season is here…” 


While Midnight’s main subject to teach Katsuki was Demon and Human History, she had an annoying habit of adding omega lectures. They were loud and long, horribly embarrassing but Katsuki learned things that he would have never learned under the watch of his parents or while being mated too long. 


Katsuki let himself ogle her body for the infinite time since becoming her student, she was an omega as well. Her body soft and voluptuous, everything about her screamed breed me in a way that still made Katsuki flush, he couldn’t imagine himself so openly approaching Izuku like that. Her tight dress, her exposed breasts and the slit up her thighs exposing skin that usually would be shown in the privacy of a room. 


“What if… He doesn’t like it? He’ll throw me out and make me live with the humans again!” 


“You’re a human, maybe it would be better to live with them.” Her teasing tone aggravating his very being, he scoffed and stood. He was done with this lesson. He wanted nothing more than to lay in his bed and sleep off his worries. 




Katsuki wasn’t one for pussyfooting if he wanted something he would sure as hell get it or he would focus on other things. He was uncertain of how willing he would be to move on from Izuku. 


He found Izuku handsome, his personality charming and kind. He had seen Izuku speak with human kings, how cold and intimidating he was to them. Katsuki had witnessed his power first hand, his innards lurching at trying to get the most capable mate. Izuku was that, power and status, a fucking king was who he wanted to sire his future children. 


He had decided, Izuku would be his! He swung open the door to the demons study. Surrounded by books on books like always, a recent shipment of new human literature had Izuku burying his nose in them any free moment of his day. 


The demon king greeted him without looking at the human. Katsuki swallowed and licked his lips, finding confidence in himself to continue forward. His collar left in his room, his shirts tighter, a few buttons left open to expose a bit of skin. Even like this he felt idiotically scandalous. 




“Mm?” Izuku’s eyes were trained on the page in front of him, his eyes shifting side to side with the words he read, impeccable speed reading at its finest. 


“I want you to mate me.” 


“Mm… Wait.” The books around Izuku fluttered in the air, some beginning to rise to the ceiling, others falling with a slap to the floor. “Wait, what? I must.. Must have misheard, I’m, what?” 


Katsuki’s cheeks red, Izuku eyes landing on him for the first time since entering the room, glowing green looking down to his neck. He watched the demon's tongue flick over his fangs. 


“I-I,” He paused to regain himself, he wouldn’t stutter, he would boast confidence in that moment. “I want you to mate me, Deku.” 


Izuku nodded to himself, processing what he had clearly heard twice now. The demon rubbed his forehead, his hand dragging down his face as he averted his eyes. He swallowed and had hundreds of thoughts rushing through his mind, from rejecting the human boy to accepting the proposal and immediately begin the mating and courting process. 


“Did you not hear me?! I want you-“ 


“Kacchan,” Izuku let out a breath. “I don’t think that would be wise on either part.” 


The demon watched as Katsuki’s face morphed, nervous to angry to disappointment. The human's eyes remained on him, his mouth twitching almost in disbelief but no words able to form and pour out. 




“You are… Young, you deserve to find a human who will make you happy.” 


“Bullshit.” Katsuki spat, another moment of silence and Izuku felt extreme awkwardness begin to itch at his scales. “If you… If you don’t want me, then why…” 


Izuku watched as Katsuki hung his head, a second later his arm cane and the demon watched his human ward wipe at the first assault of tears. Katsuki cried without making a noise, something Izuku wished he would have never mastered. 


“Maybe it’s time for you to go back to the human world.” Why Izuku felt his chest ache with pain, he didn’t know.


“You’re just going to send me away? I really am just some human, aren’t I?” Katsuki hissed, his eyes raising to glare at the demon, his nose scrunched with anger, his eyes hot with tears. “You should have left me with them, I’m sure I would have been better use to those who caught me!”  


Words he didn’t mean but he was hurt, words pouring out that caused his heart to weep, his soul to either. 


Izuku looked down on him, his tail swaying with irritation behind him and he swallowed slowly. 


“Don’t say that.” 


“I’ll say what I’d like!” The human continued, his glare unrelenting, fists clenched at his sides, palms hot with compulsive magic. “I’m sure those fucking mutts would be happy to bend-“




The omega stopped, met with an equal glare but he didn’t falter. The demon king seemed to be seething for a moment, keeping himself in check—he quickly calmed down. Izuku reached out, his hand on Katsuki’s head and when the boy didn’t move away, he let himself pet the ash blond hair. 


“Send me away now… I’d rather be alone than have your pity…” Katsuki grumbled, his glaring moving down to the space between them. 


“I… I desired for you to choose freely and now that you have, I feel like I would be taking advantage of you.” Izuku softly said, his hand sliding from the omegas hair down to cup his chin, bring beautiful red eyes to the demons. 


Katsuki scowled, he said nothing and Izuku gave him a small smile. He would have thought the alpha was smiling at a helpless animal. 


In some ways, he was just that. 


“I’d like to court you, if this is what you’d really like.” Izuku spoke slowly as if trying to convince himself as much, speaking from his hearts. 


“Court? That could take over a year.” 


Izuku nodded, “In case you change your mind. It’s what I’ll offer you.” 


Katsuki rolled his eyes, he’d rather be mated then and there but after two years of waiting, another year would be fine. 




Izuku exhaled through his nose and Katsuki watched the demon's fangs shrink and appear as regular human teeth. He went rigid as the demon leaned in and a small kiss was planted on Katsuki’s lips. 


He suddenly felt all too warm, it’s what he wanted but with only a few sneaky kisses to other demons to try and get his mind off Izuku, this kiss made his face blazed with heat. 


“Do it again.” Katsuki demanded, stepping closer and Izuku chuckled before kissing the human again. 


And again. 


And again. 


When he pulled away, Katsuki would chase his lips for a moment before staring up at him expectantly. 


“I believe you have an afternoon lesson with the High Priestess.” Izuku spoke in a hushed tone, Katsuki nodded. 


“I do.” 


“Then you wouldn’t want to be late.” Katsuki scowled and stepped away from Izuku. “Kacchan, one last thing.” 


The demon touched his bear neck, clawed fingers digging into the skin without a hint of malice. 


“I’m courting you now, wear your collar or I’ll be cross.” 


Katsuki raised his brows and a smirk played on his pink lips, his hand coming up and slipping his fingers over the alpha’s. 


“And if I don’t?” 


Izuku snapped his teeth at Katsuki and leaned down to kiss him one last time. After a kiss that lasted moments too long, he pushed the omega towards the door. 


Katsuki walked to his lesson with his head in the clouds, he was already devising plans to cut his courting time in half. 




Congratulations on the beginnings of your courting.” Toshinori set a comforting hand on Izuku’s shoulder, a smile on the old demon's face. 


I did not take you as one to partake in gossip.” Izuku said in an amused tone as they walked side by side. Toshinori was still much taller than Izuku, despite being well into a thousand years. He had lost his physical strength, no longer large and muscular but now a demon relying on magic. 


Well, maybe I listen to the gossip here and there. I believe it is your mate that has been at the center of the gossiping.” Toshinori has a wide grin, Izuku meeting his gaze with an equally wide grin. 




Some have taken it as a challenge to become the object of your affection and your mate, and well, Katsuki did not put up with it.” 


Izuku nodded, holding back a chuckle. Toshinori patted him on the back to scold him for being entertained at the idea of the young human fighting with demons. 


Katsuki is well trained, even Aizawa has given him his approval .” The king tried to explain, Toshinori didn’t seem to be buying it. “ I’ll speak with him.” 


It’s all I ask.” 




In the midst of mating season for demons, Izuku’s faux translator, Shouto, had found a demon to give his affections. Leaving the supposed non-human tongue speaking King without someone to speak to the humans for him. 


Izuku could easily talk to them but he was a sucker for dramatics, loved speaking demon tongue in front of the scared humans. Loved the way they would watch his mouth, their own jaws hanging. 


“You’re going to a festival?” 


Katsuki’s eyes went across the scroll that was sent to the edge of the Forest of Mysteries, a scout bringing it to the castle for the king. 


“I’ve been invited to one.” Izuku corrected, he stood in the middle of a summoning circle, a drop of his blood falling onto the drawn pattern. The circle glowed green, then blue and the light diminished. The king scowled before looking towards some old scriptures, his lips moving as he read silently. 


“What are you summoning?” Katsuki asked, subject of the festival dropped immediately. Izuku answering him without moving his eyes from the pages. 


“A legion of shapeshifters.” 


“Legion… An army?” 


Izuku turned to him and nodded with a fang-filled grin. “Yes, I need to be able to control them. They can shapeshift to appear human and relay information to me.” 


Katsuki blinked and grinned in return. 


“Will you send some to this festival then?” 


“You mentioned it again,” Izuku said, Katsuki finding interest on the wall of books off to the side. “Would you like to go?” 


“I don’t like the company of humans.” 


“Possibly, but you can come as my translator. Maybe use that foul mouth of yours to scare the king and the nobles.” 


Katsuki look bristled. “I’m not foul mouthed!” 


Izuku stepped towards him, cupping his cheek—he towered over the omega, tilting his head down and kissing his mate. 


“I rather enjoy foul mouthed omegas, what a shame.” The King teased. He let Katsuki grab him by the top of his chest plate to pull him back down, he relished in the omegas lips against his. “Is that a yes? Or should I bother Shouto?” 


“I suppose I have nothing else to do.” Katsuki sighed dramatically for a moment before a smirk plastered itself on his beautiful face. “I can scare them as much as I’d like?” 


“I’d be disappointed if they aren’t pissing themselves by the end of the event.” 




It was a large festival, a means as a peace treaty from the new King and Queen. Izuku has told Katsuki that this king had gone to the throne through being the first alpha heir. 


“Are they old?” 


“I believe only a few years older than you, she is the youngest and the only alpha,” Izuku explained, he was fixing the collar of Katsuki’s shirt. The omega was starting the habit of leaving his neckline exposed and that would just not do. His hands trailed down Katsuki’s sides and rested on his hips. The alpha leaned down, kissing his mate and lingered there to savor his taste. He soon opened a portal and let Katsuki walk through first. “Now, you’ll do well to be polite.”


“Polite, he says.” Katsuki grinned, licking over his lips as they came to stand in the middle of a large town square. In front of them was a large table full of food and drinks; he had not seen such well-done human food since before he went to the demon kingdom. They’re surrounded by humans, townsfolk, bibles and many, many guards. 


Their swords and spears would do nothing to Izuku, but a fatal blow to Katsuki could have the Demon King bringing the Kingdom down in flames and hordes. He kept a note to keep Katsuki within arms reach at all times.


An alpha woman immediately walks up to Izuku, dressed in white clothing, the crest of the kingdom on her chest plate. She stood straight, the heels of her boots meeting, a hand to her chest and she bows her head. 


“Welcome! I am Momo Yaoyorozu, the 17th King of this kingdom.” Her smile was wide, welcoming and Katsuki looked at Izuku for a moment. “I hope your travels were easy?”


The Demon King was eyeing her, moments passed before he bowed his head to her—her eyes seemed to twinkle when acknowledged. 


“Ask her to introduce her mate.” 


Katsuki blinked and looked back to the human King, right behind her a tall, muscular omega. In his arm, a small child with slicked black hair. He repeated as such to Momo and she gasped, a bit of a flustered look before turning her head. 


“Of course! This is my mate, Tenya and this is our son.” Momo introduced, the back of her finger touching the child’s cheek. Katsuki watched the child giggle and turn his head to hide in Tenya’s bust. The omega tried not to ogle so hard and instead found his gaze on Momo—her beautiful face that was. 


Izuku and Momo faced each other once again, his hand coming out from behind his back. Before her eyes, it transformed from a clawed beastly hand to the hand on a human man. She tried to hide her shocked expression and held her hand out to shake his. 


“She’s not scared of me, I can feel no malice from her,” Izuku spoke to Katsuki and the omega just hummed. “If the festivities go well, we will discuss the matters of a treaty.” 


Momo looked to Katsuki as he began to speak, she nodded and faced Izuku once again. 


“I hope you are able to experience the culture of our kingdom. Now, please, eat!” 


They were guided to the table of food, Izuku and Katsuki sitting on one side while Momo, Tenya and their son sat across from them. They let the couple in front of them eat to their heart's content. 


Or more so, Izuku didn’t eat as much, only tasted the food Katsuki wanted to eat as a safety precaution. Any human made poison would have no effect on him, but on his mate, it could prove deadly. 


Katsuki on the other hand, seemed to be ravishing whatever Izuku let him eat. He had nothing but Demon grub for two years, as delicious as it was, human food only made him hungrier. Izuku drank from his wine, licking his lips before passing it to the omega. 


“Could we have this in the castle?” Katsuki asked, holding his empty cup to Izuku. The Demon King sniffed the cup and nodded. 


“I’m sure it’s simple enough to make.” 


Katsuki turned his head, red eyes wide as the music began to pick up, cheeks round with a mouthful of food. 


The beat of the drums, beautiful songs playing off strings instruments, the trumpets and horns blaring. The center filled with dancing couples, parents with their excited children. He had no desire to join them but just watching them all be so peaceful and joyous made his chest fill. 


“Would you like to join them?” 


Katsuki turned his head to Izuku, the demon speaking in human tongue for the first time that night. He looked back towards the dancing people and shook his head. 


“No, I don’t know how.” 


“Then you learn, watch them and learn.” 


Katsuki grinned. “If you join me, I’ll be happy to dance.” 


Izuku shook his head and chuckled, leaning in close to the omega. “No, I’d rather watch you awkwardly join them.” 


They’re interrupted by a pair of amused chuckles, the human king and queen hide their smiles behind elegant hands. 


“Forgive us,” Tenya spoke. “It’s just, we never expected the Demon King to be so infatuated with a human.” 


Izuku blinked and scowled. He couldn’t deny it, not even when Katsuki smirked at him as a dare to try and say otherwise


“Katsuki is not just any human.” Is all he could say in his own defense. Katsuki offering him wine to which he drank from and watched his omega smile to finish the goblet of sweet liquor. 


Being there, Izuku began to realize his father was right about humans. 


Not all of them were horrible beings, he watched Momo and Tenya smile and kiss freely, watched them with their child and could only think of his own parents. How openly they expressed affection even under the eyes of others. Momo feeding Tenya a piece of cake and then their son, she smiled at them so warmly. 


Other Kings would rather be seen with whores than their own Queens. Izuku could not stand those types. 


Katsuki leaned in close, whispering on how he could tell it was human mating season. When Izuku looked, it was a pair, younger than Katsuki—red faced and dancing without a tune, bashful smiles on their faces. 


“Humans are in mating season all year round, Kacchan.” 


“I know, it’s a joke, Deku.” 


Izuku smirked and nodded, he watched the humans for a while more. 


Maybe humans were alright, after all. 


The humans of this kingdom, at least. 



Chapter Text



Izuku found the reactions that Katsuki gave him on the basis of courting was much more entertaining than the actual act of courting itself. 


His pouts, his little smiles, his eccentric smirks. Katsuki’s nasty attitude was definitely his favorite when directed at others, he loved seeing the omega boast of being the Demon King’s one and only mate. 


Katsuki was becoming more and more honest around Izuku, even if it tended to come off as being a little rude. 


It had been over a month since their courting had started, and Katsuki was back in his usual loud state even after only waking up from his heat the day before. 


They sat in front of each other, Izuku lounging in his chair while Katsuki sat crossed legged in his own chair. 


They’re both dressed much more casually than usual. Izuku abandoning all of his armor, a loose white shirt, chest exposed, and black pants tucked into his boots. Katsuki in a sleeveless black shirt and black pants, barefoot—going without his collar with only the two of them alone in the room. The pair finding no shame in staring at each other. 


“What’s the point of this?” Katsuki asked, opening his hand for Izuku to place little green paper balls in his palms—a whole total of five, no bigger than marbles. He poked them with a finger and scowled at them, they seemed like they were hollow but he just couldn’t know for sure. Izuku also had a matching five in his hand, though his were orange in color. 


“A game that couples play during the courting process.” Izuku picked a little orange ball up and smiled at it. “In simple terms, they’re truth spheres. I guess something about you and you tell me if what I say is true or false. If I guessed wrong, the ball will pop.” 


“Sounds childish…”


“To a child, it may be.”


Katsuki uncrossed his legs and kicked at Izuku’s shin, the demon chuckling. 


“So, if I have more balls than you I win?” Katsuki smirked, a little double innuendo. 


“I would have won before even courting you,” Izuku smirked back, another kick at his shin. “But yes, whoever loses all the balls has lost the game.” 


Katsuki hummed before tucking a leg under himself, he narrowed his eyes at Izuku—deep in thought. 


“Okay, any guess?” 


Izuku nods and the omega makes a concentrated face. 


“You… Were an orphan.” Katsuki stated and a moment later he looks down, a little green paper ball popping in his hand. He looks flabbergasted. “But! Midnight said most demons are abandoned by their parents almost immediately after birth!”


“Many lower demons, yes, they grow into adults within months and live short lives. Higher demons are raised just as human children are.” Izuku explains, a little cocky smile on his face as Katsuki is already one ball closer to losing. 


“Then your parents-“


“One guess at a time, Kacchan.” 


Katsuki slouched back into his chair, glaring down at his palm. Traitorous little paper shits. 


“Let’s see, I’ll guess something from Kacchan’s childhood as well.” Izuku leaned forward, his elbows resting on his knees. “You were a single child.”


They both look down at Izuku’s hand, five little paper balls all intact. 


“I guessed correctly, a single child?” 


Katsuki nodded but gave no extra information, he leaned forward as well. Only a foot of space between the couple. 


“Your father was a horrid demon.”


Another green ball popping in Katsuki’s hand, he gasped and huffed as Izuku chuckled. 


“What! Then your mother?!”


Another ball popped in his hand. His teeth clinked at how hard he shut his mouth, his lips forming into a pout, arms crossing over his chest. 


“This is stupid.” 


Izuku reached and patted his knee. “It’s just a game, my little human. Here, I’ll guess now, alright?” 


Katsuki shrugged and glared at him, Izuku knew the omega wanted him to guess wrong. He thought for a moment before nodding to himself. 


“You came from a traditional home; one omega, one alpha.” Izuku blinked and looked down, a little orange sphere popping in his palm. “Two betas? No, two omegas?” 


Katsuki looked cocky as another two balls popped, the game turning to possibly favor him. 


“A pair of alphas?” Izuku asked, a smile forming on his face when the orange spheres stayed in his hand. “Amazing, did they use a surrogate? Your mother, she carried you full term? Even in this kingdom, alpha demons have a hard time conceiving and–“ 


Izuku stopped when Katsuki snickered, a hand over his mouth. 


“I understand you’re impressed, don’t go all scholar on me.” Katsuki chided, but from the pink glow on his cheeks, he was extremely happy. Izuku smiled and leaned in, a small kiss on his omegas cheek. 


“Tell me, I want to know.”


“If you tell me about your non-frightening parents.” 


Izuku nodded, a hand coming up to scratch the base of his horn in thought. 


“My mother was a sorceress, she was very talented from what I remember, but she would panic when I used magic. She cried very much, in fear for me and my father, in glee; everything!” 


Katsuki watched as Izuku began to smile fondly, telling stories of his mother. How his habit of having things float around him came from her, whenever he watched her study magic—books, cups, pens, everything would float around her within arms reach. He spoke of his love for her, how he wishes that she was still around to this day. 


“And your father?” Katsuki hesitating to ask, Izuku spoke so much of his mother that he almost thought a bitter feeling may come up. 


Izuku looked pained for a moment before smiling solemnly. 


“My father was the previous Demon King, many called him a coward for… Never…” Izuku struggled to find the words, his eyes drifting down to the orange paper in his hand, the spheres shifting as he rolled them in his palm. “Never controlling his land properly, many humans took advantage of that and would hunt within the forest.” 


Izuku cleared his throat. A moment passes and Katsuki stays silent, he’s not sure if Izuku will continue. 


“There can only be one Demon King. My father always told me that since a young age, I surpassed him in terms of magic and strength… I was very young when I took the throne, my mother couldn’t handle it and… And followed him to his grave.” Izuku sounded pained, his voice low. His hand rubs down his face and he visibly shakes it off. “Forgive me, I didn’t… Ruining our fun mood was wrong of me.” 


Katsuki stands and Izuku looks at him, watches the omega bring his arms around his head and then his ear is being pressed against his mate’s chest. A hand starts petting his head and he’s reminded of his mother scolding him even while hugging him. Izuku didn’t know that the steady beating of a singular human heart could bring him to such tears. 


“Don’t apologize, Deku. I’m your mate, you can be a crybaby if you want, I’m not going to complain.”


For the first time in over two hundred years, he’s consoled for being the reason his parents could no longer watch him grow. 


“Well, maybe complain a little…” 


Izuku chuckles breathlessly at the tease, his hand patting his mates thigh in retribution. He smiles against Katsuki’s lips when he’s kissed—for once he doesn’t mind the salty taste of his own tears. 




They began to play this game more often, sometimes, little soft moments of emotion. 


Katsuki crying over being ripped from his mother and father’s arms, how he was forced to watch his parents’ eyes go empty. Izuku seething in anger at the thought of Katsuki, unknowing of the bandits that did it to him, having spent weeks hidden in some room of a human princess being groomed. Katsuki wouldn’t snap at her, she was beyond sweet to him, always keeping him hidden when her alpha brothers came looking for him. 


Izuku wondered if he met such princes if he would hang them by their little necks. 


He tried not to think too much of it as Katsuki kissed his lips and moaned into his mouth, to not think of anyone else but the omega in his arms. 


Izuku almost broke his own promise to himself by pushing the omega down and rutting against him. When he pulled away, Katsuki was purring and giggling, teasing him to continue. 


Izuku’s resolve was running weak—extremely weak. 


He constantly reminded himself that he still had months of courting to complete, he wanted to marry Katsuki in front of all the noble demons and his court. 


He wanted to do this properly. 


This game, however, Katsuki was playing an extremely dangerous game. They sat in Izuku’s study once again for this little guessing game. 


Izuku watched the omega roll the little spheres in his hand, a cocky smile on his beautiful face. The Demon King swallowed as he awaited the next guess to fall from his mates lips. 


“You, a demon, have two dicks.” 


They both stare at Katsuki’s palm and a moment passes, all five spheres in the omega’s hand still intact. 




“You do! I knew it!” 


Izuku chuckled and covered his face with his hands, he didn’t know why he felt his cheeks run warm but Katsuki’s smug voice was driving him up the wall. 


Maybe just showing the omega wouldn’t go against the basic made-up rules of courtship. 


“Show me.” Katsuki letting the little spheres fall onto the ground, that game abandoned in favor for another. The omega placed his hands on his alpha’s strong thighs, his beautiful jeweled eyes glistening with interest and the demon raised a brow. 


“Show you what, my rude little mate.” Izuku decided to play along, just for a little bit. His arm wrapping around Katsuki’s waist, pulling the boy in, chest to chest. He knew his limits, knew when he was being driven up the fucking wall by his alluring mate. He watched Katsuki’s pleased expression, felt soft hands touching the scales on the back of his neck to trail up into his unruly hair. 


Izuku’s eyes locked with Katsuki’s, smiles on both their faces as they shared body heat. 


“Show me what’ll be defiling me on our wedding night…” 


“I can’t do that. Don’t you wanna be surprised?”


“Or let down?” 


Katsuki leaned in, his cheek against Izuku’s. The omega letting out a humming purr as he scented the alpha, the motion making the demon’s loins stir. 


“You won’t be let down…” Izuku whispered between them, his hand lowering—allowing himself to grope his mate just this once. Katsuki didn’t seem to mind, arching his back and sighing softly against his ear. 


“I’ll show you mine…” 


Izuku’s interest was definitely piqued, he leaned back in his seat, bringing Katsuki with him. 


“Kacchan, you’re rather bold today, aren’t you?” 


The omega licked up his cheek, tongue dragging over demonic marks, the warm sensation letting Izuku know they lighted up to glow. 


“If I’m not bold, then-“ Katsuki grabbed a fistful if green hair, tugging on it. “Then you’ll never make a move.” 


“Mm, if I make a move I’ll never stop.” 


Izuku blinked as the omega pulled away, pushing the demon’s hands away. Katsuki patted himself on his pink cheeks—Izuku always forgot how easy it was to see that flushed face. 


He relaxed and watched with focused eyes as his mate pulled off his clothes, no sexual removal, just rough undressing. It wasn’t anything special until his naked mate stood in front of him, a smirk on his face; though his red ears gave away how embarrassed he must feel. 


Izuku watched Katsuki sit down in his own seat, leg rising to lay on the armrest. The Demon King feels his breath hitch as the omega slips his hand between his sweet, pale thighs. The alpha digging his nails into his palm, he wants to lurch forward. 


He can smell it, the first heavy scent of arousal. 


It’s not the first time he’s smelled it, but this time it’s without clothing, no longer muted by fabric. Katsuki lifts his soft cock, letting it lay over his thigh and his fingers spread himself. The act looks obscene in itself as if Katsuki is presenting himself to the demon for the taking. 


The first thing Izuku gathers is that it’s rather petite, rather pink, and how he would love to put his mouth on it. He looks up and feels his cheeks grow warm at how smug Katsuki looks at him, a cocky little smirk on his face at how intently his alpha is staring. 


Izuku can’t even get a word out before Katsuki is closing his thighs, crossing his legs to hide all his bits and pieces. 


“Show me yours.” 


“Mine aren’t as interesting, you’re more than welcome to present yourself again though.” 


Katsuki’s smirk turns into a pout and he glares at Izuku. 


“Hurry up, coward.” 




Izuku stands, taking a step forward. His hands undo his belt, slowly pulling it apart and he watches Katsuki’s eyes train over his groin. He pulled his pants down just to his upper thigh, enough space to give him room. The omega blinks and tilts his head, he makes no motion to touch Izuku but his curiosity is written all over his face like a kitten given a new toy. 


He supposed in phallic shape, their cocks were similar. Though, Katsuki’s was smaller, pink, cute—possibly just an appropriate mouth full when erect. He had no balls, just a pretty, supple pussy. 


Izuku’s was that of an alpha, after all, stretch marks on the base that would disappear when his knot popped, around the tip of his cock were small, rigid bumps that stayed soft even when he was hard. He assumed for pleasure more than any other function for mating. He hadn’t received a complaint thus far. 




Izuku snorts and Katsuki stares up at him with wide eyes, mouth opened in surprise. 


“Yes, it is.” 


“Where’s the other one?” 


Izuku touched a dark slit, right above the base of his cock. Katsuki watches as the demon pressed lightly on it, a slimy bright green tentacle poking its head out. It comes out only about a fingers length to curl over Izuku’s finger, a slick watery substance left wherever it touched, or slides over. 


The demon is pleasantly surprised when his omega reaches out cautiously. He watches the omega squirm as the tentacle touched the tips of his fingers. It feels like a slimy hot worm, like the ones he would find when he first explored the creepy gardens of the castle. 


“That’s not a dick!” Katsuki’s face is littered with obvious surprise, but his eyes or hand never wavers; the tentacle slipping between his fingers, almost licking at his at the pads of his fingers. 


The thick tentacle seemed to have a mind of its own. 


“It is, just not the type humans have.” Izuku explained. 


Katsuki didn’t look too convinced, pinching the tip of the tentacle made Izuku’s hips buck and the boy suddenly found his slight disgust with the tentacle replaced with a curious warmth. 


The omega momentarily wonders how it would feel wrapped around his dick or even better, squirming inside of his own wet heat. 


“Does it feel good? Using this?” 


Izuku nodded slowly, his eyes half-lidded, his heavy tail swaying restlessly at the omega heavily petting his slippery cock. Katsuki’s beautiful red eyes filled with mischief and wonder. 


“It does.” 


“Would you put it inside me?” 


Izuku lets out a heavy breath. “I’d put both…” 


Katsuki blinks and grins widely. Both he and Izuku know that the demon is losing it, how such little teasing could make him consider abandoning their courtship. 


Izuku pulls away, pulling his pants up with a shuddering breath. Katsuki’s hand left soiled with the tentacle’s watery green slick, he stared at it and without even thinking twice, brought his hand up. 




Too late. 


The omega brought his hand up to his mouth, tongue licking over the fluid. He made a strange face, his nose scrunching up as he pouted. 


“Why is it sweet?!


Izuku tilted his head in question, grabbing Katsuki’s wrist to prevent him from taking another taste. He pulled a cloth from his shirt pocket and wiped the omega’s hand clean. 


“It’s usually sweet, why are you surprised?”


“Mine isn’t sweet.” 


The demon paused for a moment, his eyes wide. He furrowed his brow and was met with an equally confused expression on Katsuki’s face. 


“Yours? But you have a healthy diet, if there’s something wrong, you have to tell me. I’m sure a doctor can figure out–“ Izuku cut himself off, he was taking this in the wrong direction. Katsuki was human, their anatomy much different. Nothing was wrong with his mate, they were just a different species. He had to relax. “What does… It taste like?” 


Katsuki snorted, a hand coming up to hide his grin. His voice muffled behind his hand. “Sort of salty.” 




Immediately, a book and pen come over, just next to Izuku’s head; papers turning quickly before stopping on a page. Katsuki couldn’t hold back his snarky laugh as the pen began to scribble away on the paper. 


Izuku wasn’t able to pull more information from the omega, no matter how much he asked or questioned. 


Katsuki kissed him, a little tease that the demon will just have to find out on their wedding night. 








Izuku looked over his mate’s shoulders, looking down at a complicated spellbook. 


“Is there something specific you seek? I could help you find it quickly, I’ve read the entire book.” Izuku offered, only to have a small hand smack him right on the nose. He pulled back and the omega turned his head to glare at him. 


“Why can’t I read half of this? Did you enchant it?” Katsuki growled, looking back down to the book in his hand, flipping the pages quickly. “Look! Like here, I can’t read this spell!” 


Izuku looked to where Katsuki pointed, a summoning spell in the language of his ancestors.  


“It’s not enchanted, just in the old tongue.” 


“You can read it?” 


“I can.” 


Katsuki made him translate the spell for him, his brows furrowed as he tried to understand it in his head. 


“I’m sure with a bit more study, you’ll be able to understand it.” 


“I want to try it now.” 


Izuku blinked and gave a nervous chuckle. “Kacchan-“


“I want to try it now!” 


Katsuki all but stomped his foot on the ground like a child, his glare heavy. From an outsider's perspective, they wouldn’t have assumed an omegan human was talking as such to the King of Demons. 


“Katsuki, it’s dangerous.” 


“I don’t care. Anyways, you’re here, so I’ll be fine.” Katsuki stepped closer, leaning up to kiss his alphas jaw. When he pulled away, he searched for any sort of consent from Izuku and when the demon’s eyes looked off to the side—Katsuki knew he had won. 


He watched Izuku clear a space for him in the study, stepping to the side to observe and step in if necessary. 


Katsuki’s palm lit up with an orange glow, the book opens in his other hand. He repeated words he did not know the full meaning to, the floor around him beginning to glow and form into a summoning circle. He continued the smell, his heart racing as his hand began to burn; it was so much more different than when he used explosive magic. 


This magic was much stronger than he was, much more terrifying. 


He finished the spell and watched as a large portal opened on the floor around him. He took a step back, bumping into Izuku’s chest. He looked up and the demon glaring at the summoning circle. 


For the first time in two years, Katsuki felt like he made a massive mistake for toying with this magic. 


Katsuki’s blood ran cold, a strange, creepy noise began to ring in the study. His eyes trained on the portal, the light-emitting from it shifting in colors. It stopped on red and just as it started. 


It ended. 


Smoke fumed from the portal and Katsuki’s hand stopped burning. His fingertips touched the skin of his palm and he could feel a seal edged into his flesh. 


“Ma… Ster…” 


Katsuki couldn't take his eyes away, two red eyes glowing at him from within the smoke, low to the ground. He swallowed as the air cleared, he would be faced with his first summon. 


Katsuki’s face erupted with a grin, his first summon, his heart wouldn’t deceive him.


He had just summoned something powerful, something to be feared by the masses. 


He had summoned...


A six-legged white cat. 


“What the fuck…” 


Izuku placed a hand on his shoulder, a smile on his handsome demonic face. 


“Congratulations, my powerful little sorcerer.” 


“Don’t patronize me!” Katsuki smacked Izuku’s hand away, pointing at the feline—who so innocently licked at its fur. “What kind of spell was that! You said dangerous!” 


“It is dangerous, for your first summon I would have liked a fairy or even a friendly golem!” Izuku argued, but his smile never left his face. He leaned in, kissing Katsuki’s temple. “I’m proud of you.” 


“Shut up… I was imagining a dragon or something…” 


Katsuki walked into the cleared air, picking the cat up, holding it in his arms like an infant. The cat’s pupils turning large as he? Katsuki looked down, a female. As she looked at her master. 


“What now?” 


“Take care of her, feed her. Aizawa can teach you on how to get rid of a summons.” 


Katsuki pouted, his hand already petting the thick fur of her belly. He wouldn’t say out loud how soft she was or how he wanted to play with her.  


“I can name her?” 


“Yes. She’s just like Scelia and Iythe, a pet or a guardian if you wish.” 


Izuku leaned in, a smile on his face, his finger about to poke the cat’s belly just as his mate but he hissed when scratched. His green eyes glaring down at his scratched finger, the nails feeling an exaggerated burning sensation. His finger healing up within seconds but just the thought of being injured by the creature let a bitter taste in his mouth. 


“Hey!” Katsuki glared down at her but she let out a small pleased noise, he seemed to instantly forgive her and his eyes turned up to look at Izuku with a faux apology. “You surprised her, she’s sorry.”


“Summoned for a few minutes and you already side with her?” Izuku almost growled at his mate but if he had hurt the omega's feelings, it wasn't shown on his face. 


Katsuki smirked and looked to the side. “No…” 


The cat never left Katsuki’s side, or at least let him out of her line of sight. She lounged in the bookshelves, pawed at passing books or items. She hissed at Izuku and when the demon tried to find out the reason, Aizawa just rolled his eyes. 


“Summons are only loyal to their master, don’t take it personally.” 


Izuku was reminded that before Katsuki, his summons were very much the same. Months pass and the cat never took a liking to the demon, hissing, scratching at his ankles when he walked by. He couldn’t even accuse her when all she did was rub herself against his chuckling mate, both seeming to purr with each other. 


They were a sight for sore eyes, but it didn’t stop from getting on his nerves day in and day out. 


Though, after Mania, Katsuki was not able to summon another sentient being. As Izuku wanted, he summoned a few large golems. Katsuki using them to spar with, to expand the area of explosions that he loved created. The mindless golems making amazing targets for the omega to wreak havoc on without any sort of consequence. 


Katsuki still convinced he would unlock something within Mania, something that would cause her to evolve in a way. He must have had a large, powerful feline like creature in his mind so he persisted with the summon.  


Izuku rather have had any of those mindless summons compared to the six-legged cat that hated him. How dare such a lowly creature to think she was on par with the Demon King, if it wasn't for Katsuki's fondness towards the feline; Izuku would have long killed it for its insolence. 


“Are you seriously pouting?” 


The demon scowled and turned his head up to his smirking mate, the summoned cat lounging on Katsuki’s shoulders—the end of her tail flicking slowly as she seemed to glare at Izuku. 


“I’m not pouting.” Izuku sighed before patting his thigh. ”Come here.” 


Katsuki took his angry summon off his shoulders, placing her on the floor before going to straddle his king. His arms, like clockwork, linking around Izuku’s shoulders. Both of them sitting chest to chest, flush against one another. 


“Don’t be a brat.” Katsuki chuckles, leaning in to press his lips against his soon to be husbands. The alpha happily returned the kiss. “Mania will come around, one day.” 


“Why did you even name her that…” Izuku complained, his question dying in the air as he was kissed again. Katsuki made himself comfortable in his mate’s lap, hips rocking slowly, but large hands grab at his waist to stop him before either of them could truly start feeling the excitement or arousal. 


“Just a while more… We’ll be married…” Izuku took Katsuki’s hand, kissing where he would brand his mark on the omegas wrist. “And I’ll give you all the pleasures of this world that I can offer…” 


Katsuki huffed, leaning in and biting the alphas cheek. 


“You better make it worth it, Deku.” 


“I’ve also prepared our wedding gift.” 


Katsuki’s expression change from annoyed to curiously excited. 


“I should prepare a gift as well?” 


“I’ll take my gift from your body, you don’t have to worry.” Izuku took his omega's lips once again, allowing himself just a few greedy moments. Katsuki sighing pleasantly against his mouth, head tilting to match the alphas moves. 


Izuku felt himself on the last bit of strength. 


Within one moon cycle, when the red moon rises to its peak, he will have taken the omega in his lap for his own. He would mark and savor the taste of his delicious treat of a mate.