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The Demon Inside

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Quirks. The phenomenon that society revolved around.


Villains, with powers that allowed them to wreak havoc. 


And heroes, with powers that enabled them to step up to meet them.


Children would excitedly wait for their fourth birthday, when their quirk would develop, finally giving them their place in society while simultaneously setting them apart from their peers. Every child would hope for a quirk that allowed them to become a hero.


And those that didn’t have quirks at all were shunned and beaten down by a society that, barely two centuries beforehand, was just as powerless.


So yes, the world revolved around quirks.


Izuku Midoriya was one of those children. Waiting with bated breath for his quirk to develop.


His best friend, Katsuki Bakugou-or Kacchan, as Izuku called him-had already gotten his. He had been defending Izuku from another kid, a year older than them, when suddenly, small pops and explosions began forming from his palms. This had drawn the attention of the teacher, who quickly chased away the bully.


Now it had been almost nine months since that day, about six months since Izuku’s own birthday, and he was still waiting for his quirk.


What’s worse is that he’s been watching Kacchan change. It’s been subtle, slow, so not many people had noticed, but this was his best friend, the changes were obvious to him.


Ever since he got his quirk, Bakugou had been growing more and more arrogant with every compliment and every bit of praise he got. So much so, that he had begun to look down on other children; viewing himself as above them all. He was even starting to bully some of the ones with quirks that he thinks are ‘weak’ or ‘useless’.


Bakugou hadn’t even noticed that the bully he’d been fighting on the day his quirk developed, was now following him around joining in on all the bullying.


So far, Bakugou hadn’t done anything to Izuku, hadn’t targeted him for not having a quirk. But he had left him behind; completely ignoring him and leaving him out of any games he played. The only time he even interacted with Izuku at all was when he tried to stop Bakugou from bullying someone else. He’d tell Izuku to shut up, and that they deserved it for being weak.


Now, Izuku was on his way out of the school after the end of another day. He had just walked out through the main doors when he felt something weird in his mind. It felt tingly, almost fuzzy. It was anger, not his own, but someone else’s.


Even weirder; the feeling was moving. It started in the left side of his head, but when he turned in that direction, it moved to the front. It was directing him; whatever this new feeling was, it was pointing him towards something.


Curious as to what it was, he followed it, walking in the direction it was pointing him. He rounded the corner, coming to the side of the school building, and found the source of the new feeling.


Bakugou and two of his ‘friends’ were standing over another kid, who was lying on the ground. He had a triumphant smile on his face, small explosions popping from his hand as he looked down at his victim. Said victim was nursing a nasty burn on his shoulder and had tears pouring down his face, either from pain or fear.


Just as it looked like Bakugou was going in for another strike, Izuku ran forward, placing himself between him and the kid on the ground.


“Stop it Kacchan!” He yelled. “He didn’t do anything to you!”


A sneer grew on Bakugou’s face as he looked at Izuku. “So what? We’re teaching him his place. He’s weak and useless and he needs to remember that.”


“You- You’re being a bully Kacchan. You need to stop.”


Bakugou’s sneer quickly morphed into a scowl at Izuku’s words. “Oh? And are you gonna stop me? ‘Cause you’re just as weak as him. You’re just a useless Deku.”


Izuku’s breath caught at that. This was the first time Bakugou, his friend, had ever said anything like that to him. The kid on the ground quickly got up and ran away, not even looking back.


“Y-You don’t mean that Kacchan.” Surely, he didn’t, he was just caught up in the moment.


“Of course I do, Deku. You’re weak and useless. You don’t even have a quirk yet. Maybe you’re quirkless.”


“N-No I’m not Kacchan. I’ll have a quirk; it just hasn’t shown up yet.”


“No you won’t, stupid Deku. You’re gonna be quirkless and useless forever.” His scowl grew darker. “Maybe we should teach you a lesson too, since you seem to think that you can stop me even though you’re so weak.”


“Wait, Kacchan s-stop!” He yelled, as Bakugou stepped forward. An explosive palm shoved him, burning him in the same spot as the other kid had been.


Izuku stumbled back a few steps, uniform smoking. He saw Bakugou walk towards him, ready to hit him again. He was about to turn and run away, when he felt something inside of him shift.


His vision suddenly became sharper, followed by his hearing. He felt something weird happening with his ears and his fingers felt warm and tingly, as did his lower back.


Before he could think about it too much, Bakugou’s hand was rushing towards him once more. But something was wrong; it was a lot slower than it should’ve been. Izuku watched it as it moved through the air.


Then, his body seemed to move on its own, instinct or something else taking hold. He reached out and grabbed Bakugou’s wrist, twisting it to the side. The explosion that had been meant for him, instead detonated off to the side. He could see that the hand wrapped around Bakugou’s wrist, his hand, had inky black claws where the fingernails were supposed to be.


He felt anger rush through him, hot and volatile. Bakugou, the person who was supposed to be his best friend, was attacking him and trying to hurt him. Why was he being such a bully? Such a villain?


“Kacchan.” He said, surprised at his own voice; it was a lot deeper than it was supposed to be. “I said stop.”




Katsuki was getting annoyed. He and the others, the annoying extras who tagged along behind him wherever he went, had been trying to teach this weak nobody their place, when that useless nerd jumped in to try to stop him.


The nerd, Deku, had tried to tell Katsuki to stop; that he was being a bully. Who did he think he was? Thinking that someone as weak as him could tell Katsuki what to do.


He’d been nice to the nerd so far, waiting for him to get his quirk so that they could go back to being heroes together, but he was getting impatient. He still hadn’t gotten his quirk yet, even though it had been six months since his birthday. Maybe he was quirkless, the weakest of the weak; worse even than the people with useless quirks.


Maybe he just needed to teach Deku a lesson, show him that no matter what, he’d always be weaker than Katsuki. Show him that no matter what he did, he’d always be useless.


So, he did. Ignoring the nerd’s pitiful yells for him to stop. He used his quirk, burning the stupid nerd’s uniform. Deku had a look in his face, shock and hurt at what Katsuki had just done. Up to this point he’d never done anything to him, even when Deku tailed behind him like one of the extras and tried to stop him from showing someone their place.


He stepped forward to hit Deku again, palm popping in preparation. However, when he sent his hand forward, something caught it and he felt his wrist being twisted harshly to the side.


It was Deku. The nerd had a different look on his face now. Anger and fierceness that he’d never been able to show on his useless, timid face before. His hand had claws, black and menacing, that were a hairsbreadth away from digging into his arm. Katsuki could see fuzzy ears sprouting from the top of the nerd’s head and a long fluffy tail, the same green as his hair, hanging from his lower back.


And his eyes.


His eyes were a deep bloodred. Filled with more anger than Katsuki could comprehend. His pupils were black slits.


“Kacchan.” He heard Deku growl. His voice deeper and more gravely than it should’ve ever been. “I said stop.


The sound of his voice combined with the look in his eyes triggered Katsuki’s fight or flight instincts. He lashed out with the hand that wasn’t being restrained, aiming for the head this time.


But, like the other, this hand was caught before it could hit anything. A growl ripped out of Deku’s throat, primal and angry. Katsuki looked behind Deku to see another tail join his first. The claws on the hands holding his wrists started to grow even longer.


Katsuki started to panic. Both of his attacks being blocked so easily made him feel powerless, and that feeling did not sit well with him. He tried to jerk his hands out of Deku’s grip, to no avail. The nerd was like a stone wall right now, not budging an inch.


“Let me go you useless Deku!” He yelled, trying to hide the fear in his voice.


“Stop bullying people Kacchan.” Deku said, in that same growling voice.


“What are you talking about!? Just let me go!”


“Stop bullying people.” He repeated. “If you want to be a hero, then you’ll stop. Right now, you’re acting like a villain.”


With that, the nerd finally let go of Katsuki’s wrists. Since he had still been struggling to pull away, the suddenness of his release sent him falling back on the ground.


One of the useless extras shouted out from behind him. “Shit! Let’s get out of here! C’mon Bakugou!”


Ignoring them, he scrambled back to his feet. He looked at Deku as he backed away slowly. The nerd was still staring at him with that same look in his eyes. Without another word, to Deku or the two extras, he took off running. He rounded the corner, to the front of the school. He could hear the extras shouting after him, but he didn’t stop, he didn’t stop running until he made it back home and was safely inside.




Izuku was panicking. It had been a few minutes since Bakugou and the other two bullies ran away. Now that he was starting to calm down, his thoughts were quickly beginning to spiral out of control as he replayed the events of the last several minutes.


“Okay so I actually stood up to Kacchan and saved the other kid and I finally got my quirk. And ohmygosh I actually have my quirk now, it looks like some kind of dog transformation. But that’s not important I can’t believe I just attacked Kacchan! I just attacked him and he’s probably so mad at me! I’m probably gonna get in tr-”


“You didn’t attack him, Runt.” He was pulled from his thoughts by a voice.


“What? Who said that?” He questioned, unable to determine the source of the voice. “And what do you mean I didn’t attack him? I just did!”


“I said that.” The voice replied. “And no, you didn’t. He attacked you. All you did was stop him from hitting you.”


“Hmm. I guess that makes sense.” He relented. “But wait. Where are you? Why can’t I see you?”


“Because I’m not out there. I’m in your head.”


“Huh? In my head? What does that mean?” He thought about it for a moment, before realization sparked. “Wait a minute. Are you my quirk?”


“Obviously, Runt.” The voice said, sounding amused. “How else would you have been able to catch that kid’s hands before he hit you?”


“That was you?” He asked, recalling how his body seemed to move on its own to stop Bakugou’s attack.


“Of course. I wasn’t about to just let you get hit.”


Izuku smiled, feeling the protectiveness radiating from the – whatever it was – his quirk. He took a moment to examine the changes to his body.


The claws on his fingertips were about half an inch in length and looked razor sharp. It was a wonder that he hadn’t cut Bakugou when he’d grabbed him. Then again, if the voice in his head was the one controlling it, then maybe he’d made sure that Bakugou didn’t get hurt.


He touched the top of his head, feeling the new pointed ears that were present there; they felt soft. Looking behind him, he noticed the long, fluffy tail sprouting from his tail bone. But, something felt off. For some reason, it felt like he was missing something. When he was defending himself from Bakugou, it had felt like he’d had a second tail. Was that why he felt off?


“You did have a second tail. But it’s gone now that you’ve calmed down.”  The voice in his head answered his unspoken question. “It’s not gone forever. It’ll come back if you need it again. Or once you’ve learned to control it.”


“Huh. Okay.” It still felt off; not having the second tail. But the voice said it could come back, so it must be okay. He trusted the voice in his head, even if he only became aware of it a few minutes ago.


Izuku wanted to know why the second tail even appeared in the first place, and if there were more tails beyond that. He was about to ask, when he had another realization.


“Mom.” He said out loud. “I almost forgot about mom! I need to go home and tell her that I finally got my quirk!”


With that, he hurried home. It seemed to take less time than usual for him to run home. His legs seemed to carry him faster than they used to.


Because of this, it wasn’t long before he was walking through the door into the apartment that he and his mom lived in.


“Mom!” He called out excitedly as soon as he opened the door. “Mom!”


“Izuku?” His mom responded from within the apartment. “Izuku, sweetheart. What is it?” She entered the kitchen with a slightly concerned look on her face that quickly vanished, replaced by one of surprise upon taking in his expression and the new features adorning him.


“Mom! I got my quirk today!” He announced with a huge smile on his face.