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Published:
2025-10-11
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2026-08-19
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From Another Time

Summary:

“Look carefully at his breathing,” She said, “Don’t be afraid to get close.”

It was almost unnoticeable at first, but if he listened, he could hear water. Like he was at a beach with waves calmly washing ashore. It was calm and peaceful. He swore he could smell the salt.

The nurse almost laughed at them. “Yeah, that's kinda the reaction we had. Never seen a quirk like it."

 

A MHA and Demon Slayer crossover.

Chapter 1: Discovery

Chapter Text

His body moved before his eyes could open. Fueled by the underlying survival instinct to move, long installed into him by his Master. 

 

Something was wrong. Very wrong.

 

He opened his eyes before tightening them closed again. It was horribly nauseating. The environment moved and blurred. Even in his impaired state, he knew his sight would be of no use. Colors, smells, and sounds smashed his senses, all of them different, all of them wrong. Creating a blended symphony of overstimulation. 

 

Something heavy settled in his chest. Unease that chilled his bones and forced action.

 

Confusion muddled his brain as he toppled over. Falling flat to his stomach after his unsuccessful attempt to climb to his feet.

 

He couldn’t open his eyes again, he couldn’t solve the puzzle of what exactly was going on. He knew he wasn’t alone before he got here (wherever he was), but the familiar comforts he was craving were replaced by strangeness. 

 

That burning stubbornness willed him to move, despite the pain, despite the blurring of his eyesight. He gagged, forcing his hands in front of himself, dragging himself along the cement to cover through squinted eyes.

 


What was supposed to be a day filled with competition, cheering, and friendly battle took a sour turn.

 

Two police cruisers parked themselves outside a shipping warehouse. The road on both sides was closed, as one officer finished blocking off the intersection, preventing the prying eyes of curious onlookers. Frustrated commuters honked their horns, stuck behind the tape with nowhere to go, and with no idea when they would be able to move again. 

 

Kamui Woods could see six officers as he got out of the car. So much for working security at the festival; he knew whatever occurred here would likely take up his attention for the duration of his shift. 

 

“What’s going on?” Kamui Woods asked, already scanning the environment as he approached, Mt. Lady following close behind.  “The dispatcher informed us of a  potentially powerful villain in the area.”

 

One of the officers nodded, pointing down an alley behind the warehouse. “Y-yes,” He stated professionally, obviously a more seasoned vet. “A citizen called about obsessive amounts of blood they had witnessed while they were taking out the trash.” He gestured, “From here, we believe we can see an injured person behind some bags. We tried to call out to them, but the victim isn’t responding.”

 

Kamui Woods turned, facing the entrance of the alley and stepping closer to it. 

 

Mt Lady crouched down next to him, her face hardened. “Look.” She prompted, her voice tinged with something unidentifiable. 

 

Peering down, just inches from his feet was a trail of blood, like the victim had been dragged deeper into the shadows. 

 

Following the blood stains, as the officer confirmed, two bloody legs were sticking out from a dumpster. A growing puddle of red leaked onto the cement. 

 

Kamui’s fists tightened, fighting the urge to rush to their side. It wouldn’t benefit anyone to skip gathering the facts. “Why haven’t you provided aid? The person requires help.” He snapped, looking at Mt. Lady, her own face twisted in anger.

 

“Because of that-” The officer stuttered, pointing further down the dirty alley. Kamui wasn’t sure how he missed it at first glance, but lying haphazardly was a bloody weapon, a sword.

 

Mt. Lady took a breath. “Stain.” She mumbled harshly, shoving the officer aside and running towards the victim. 

 

Kamui Woods cursed, quickly following behind her heels. “Mt. Lady, stop!” But she ignored him, swiftly closing the distance between herself and the unknown person. 

 

Lady fell to her knees as she reached the injured person, gasping as she placed her hands on the biggest wound, a large cut in his shoulder still actively bleeding. It was a child. A very, very injured child. 

 

Kamui Woods fought off the urge to freeze. This child couldn’t have been older than the students currently having a friendly tournament. He wasn’t just wounded, but looked like he had been tortured. His eyes, mouth, and limbs were leaking blood at a concerning rate, creating a massive red puddle under his clothes. 

Tearing his eyes away, he looked around the alley for any signs of ill intent.

 

“Kamui!” Mt. Lady snapped, her uniform already soaked in blood as she stuck to the boy's side. “He’s losing way too much blood! Get the EMTs here! Now!”

 

The pro gestured to the entrance, waving over the ready EMTs, both of them shifting back and forth anxiously. “Over here! Bring a stretcher!”

 

He turned back to the boy, closing his eyes tightly before scaling the wall to the roof. He was no help here. The only thing to do was to make sure whoever did this wasn’t still in the area to finish off what they started.  

 

The emergency services dismissed Mt. Lady, taking her spot and shoving her aside. Mt. Lady ran her bloody gloves down her thighs, a poor attempt to rid herself of the blood before joining her partner on the roof, providing lookout. 

 

“We need to get him in the ambulance!” One shouted, looking over the wounds, his face pale. 

 

“Are you kidding?” The other snapped, already pulling out a white wrap and piling her weight onto his shoulder. The boy groaned at the pressure, but did not move. “He’s already lost way too much blood; we need to stop the bleeding here and now, or he’s going to die!”

 

“No-” The other EMT argued, his glare burning. “His biggest wound is on his chest, which we can’t wrap without cutting off his clothes first, which will take way too much time. We need to get an IV in him while we wrap him; it's our only option!”

 

The EMT bit her lip, but complied, helping her coworker lift the teenager onto the clean stretcher like a rag doll. Droplets of blood fell behind him.

 

Mt. Lady flinched. His body was limp and weak. She’s worked cases with children involved before, but nothing like this. Blood covered every inch of his skin. It made her sick. She tore her gaze away as he was loaded into the ambulance. She tried not to gag as she pictured any of Aizawa’s students in his place, students she helped not too long ago pick their hero names. 

 

With the all clear, police had already started investigating the alley, watching out for any danger as they analyzed the scene.

 

With the immediate threat gone, Mt. Lady scaled the wall to place herself next to the other hero. 

 

Both pros stood in silence, listening as the emergency vehicle got further and further away till it couldn’t be heard anymore. 

 

“Did you see it too?” She asked, her voice tight as she watched an officer pick up the forgotten sword. 

 

Kamui ground his teeth. “Yeah. I did.”

 

Things just got much more complicated.


UA was always bustling. There was never a dull moment at the school, especially with the new first years who could never seem to keep out of trouble.

 

Nezu hung up the phone, his jaw tight despite his neutral expression. He knew that Aizawa would be grumpy about this decision, but All Might shouldn’t have any difficulty managing class 1-A for a few hours. 

 

The principal hummed and folded his paws onto his desk, waiting patiently for the homeroom teacher.

 

His office door was given a soft knock. Nezu gave an acknowledgement as Aizawa dragged his feet inside, his eyes tired.

 

“What’s going on, Nezu? You don’t usually pull me out of class.” He asked, taking a seat in front of the wooden desk, annoyance clear in his tone. 

 

“Ah, yes,” Nezu nodded, pulling out the notes he had taken during the phone call, “I know you hate to be brought away from your students. However, this is a request both from myself and from Detective Tsukauchi.” 

 

Aizawa raised an eyebrow, “Must be pretty important then.” He sighed, leaning forward. He had hoped that with his students' relatively good behavior today, he would have an easy afternoon. Apparently not.

 

“Very.” Nezu clarified. “Two days ago, a child was found in an alleyway with extensive injuries. He is now officially out of the danger zone according to the doctors, but his healing progress has had an immediate halt."

 

  “Halted? How can they declare that if he was just administered this week? If his injuries were that severe, then the staff should know that he wouldn’t get better overnight.” Aizawa questioned, swallowing a lump of anger in his throat. 

 

“Yes, but the situation is…strange,” Nezu stated, reviewing his notes before looking back at Aizawa. “He’s not in any database, not even when run through foreign databases. It’s like he doesn’t exist.”

 

Aizawa sighed, pinching his nose. It was an unfortunate reality, but they might have stumbled on a trafficking case. “Alright, but that doesn’t explain why the hospital wants to rush recovery.”

 

Nezu refoled his paws, his smile tight. “They believe his quirk is disrupting healing. A few doctors and nurses have been using their quirks to speed up his recovery, but yesterday, all signs of healing stopped, and the child started an abnormal breathing pattern. They fear that his quirk is unintentionally hurting him.” 

Aizawa’s lips straightened out. “And they think I can stop his quirk?” 

 

The bear nodded, “Yes, they believe so. They are afraid he will perish if he continues to use his quirk, as they have no idea what it is exactly.”

 

The teacher leaned back. It wasn’t a question whether he would assist or not; of course, he would, but he wanted answers. “Fine, but I want the story, the whole story if I’m getting involved in this.”

 

Nezu waved a dismissal paw, a smile on his face. “Yes, yes of course. The commission was insistent on keeping you in the dark, but you deserve the truth if you are providing aid.” He confirmed, “But this is confidential.”

 

Aizawa nodded,  knowing that if the commission was involved, it was sure to be a mess. 

 

“They believe the boy's attacker is Hero Killer Stain.” 

 

Aizawa felt his blood chill. Whatever he had been expecting wasn’t that. 

 

“What? Why the hell would Stain attack a child?”

 

Nezu shook his head. “We are unsure. It is yet another reason why the Detective wants him to awaken for questioning. The child is not a hero student, so in theory, Stain would have no business with him. “

 

“Why do they think it was Stain? This doesn’t really seem like his style.” Aizawa asked. He’s seen the aftermath of a Stain attack. It makes him sick to think of a child being on the receiving end of his weapon.

 

“They found a bloodied sword next to the child.”

 

Aizawa leaned back again, letting out a breath as he processed the information. “Alright, what's the extent of his wounds?” He asked, bracing himself. 

 

The other shook his head. “It's better if you find out from the hospital staff. They can likely explain it better than I can.”

 

Somehow Aizawa doubted that, but there wasn’t a point in arguing it. The teacher stood, digging his hands into his pockets. “Give me the address.” 

 


The hospital was relatively bare of citizens.  A bright side to a terrible situation. With All Might being in town to teach, crime had significantly reduced. 

 

Aizawa’s hands hadn’t left their pockets since leaving Nezu’s office, hiding his tightened fists behind the fabric.

 

The elevator doors opened. Two police officers stood watch in the room labeled 365. One stood up to greet him, extending a hand in greeting. “Eraser, we're glad to see you.” 

 

The Pro shook his hand before shoving it back into his pocket. “Where is the nursing staff? I have a few questions for them.”

 

The officer gestured with his head towards the door. “They're already inside. I think they are changing some bandages.” 

 

Eraser nodded as both moved aside, letting him twist the nob. 

 

It was worse than he could have imagined. 

 

He couldn’t have been older than any of his own students. Almost every inch of his body was wrapped snugly in white, his right arm being propped up with a sling.

 

He felt sick all over again.

 

A nurse was tending to an injury somewhere on his face. Aizawa couldn’t make it out due to the angle. 

 

“Oh!” The nurse looked over her shoulder, “Hello, you must be the pro that the Detective sent.” She smiled sadly, turning back to her work.

 

Eraser stepped closer, attempting to get a view of what she was doing without interrupting her. “Yes, I do need a few details before using my quirk.” He clarified, “Is the Detective on his way?”

 

She used her scissors and cut the bandage from the roll, reaching over the victim's jaw to keep it in place. “Yes, I believe he should be here soon.” She nodded, “I can debrief you in the meantime.” 

 

He stepped out of her way as she placed her supplies back onto the tray table. Unshed tears glanced in her eyes. “It- This is the worst condition I’ve ever seen a teenager in before.” She confessed. 

 

Eraser took another look. It was sickening to see the blood staining the freshly changed white bandages, but beyond that, there was something he wasn't able to notice at first glance.

 

This kid was in amazing shape. Muscles peeked out from behind his wrappings, not unlike some of his more active students. 

 

Was he a vigilante? Was that why he was attacked by Stain? 

 

The nurse spoke again, drawing Eraser’s attention. “Upon arrival, he was bleeding from his eyes. We aren’t sure why this occurred, but we believe it was a quirk overuse. He had 3 broken ribs, lucky none punctured his lungs, two broken fingers,” She said, gesturing to the teen's right hand, before swallowing a breath, “and two stab wounds.” She directed him to his right side,  “The worst was done to his shoulder down to his chest, and the other was done at the bottom of his jaw.” She said, removing her hands from his shoulder to his mouth, gently tilting it upwards. “Both stab wounds needed stitches.”

 

Aizawa put a comforting hand on her shoulder, his own body tense with rage. It was absolutely disgusting. How much fear, helplessness this teenager must have felt as he was beaten. 

 

The nurse backed up from the bed, quickly smearing her tears away. “He, um- he’s also inflicted with many self-defensive wounds.” She choked, gathering her tools, turning away from the hero like she was ashamed to cry. “Many bruises and smaller cuts covering his legs and forearms, like he was defending himself from attack.” 

 

Aizawa was the worst at providing comfort. He didn’t have the people skills to reassure others, a large reason why he was an undercover hero, but it is wrong for the nurse to feel less than for showing empathy. 

 

“Don’t worry,” He said, his voice gruff with his own firm anger. “We will find whoever did this, and they will never lay another finger on him again.” He clarified. 

 

The nurse's shoulders loosened, and she brought another hand to her cheek as she cleared her throat. “Yes, I-I’m sorry.” She turned back towards him, the stray tears gone. “I have a child at home his age,” She confessed. “This just…makes me so angry.”

 

Eraser briefly thought of his own problem children, closing his eyes. “I understand, it makes me angry too.” 

 

The door opened again, closing as the Detective stepped inside. 

 

“Sorry, I am late,” He apologized. “I’m assuming you were caught up?”

 

Aizawa nodded, looking at the nurse's name tag as he removed his hand. “Yes, Ms. Chiyo informed me of everything.”

 

She smiled lightly, but it didn’t reach her eyes. “I am glad to be of help. The only thing we did not cover was the boy’s suspected quirk.” She said, grabbing her stethoscope off the metal tray. “I’m sure it's been communicated to you, but the doctor is worried that his quirk has slowed down the effects of medicine, which could increase the risk of infection.” She bit her lip as she hung the tool around her neck. “Considering how deep they are, an infection would likely be lethal.”

 

She placed the stethoscope against his chest, listening for a few seconds before stepping back. “His heart rate is considerably slow, which might be his baseline, but we have no idea.”

 

“Then why do you suspect a quirk?” Tsukauchi asked, sharing a glance with the hero.

 

The nurse took the stethoscope off and put it down. “Look carefully at his breathing,” She said, “Don’t be afraid to get close.”

 

Tsukauchi walked next to the bed, leaning a bit closer to the boy's face before stepping back in shock. “What the hell?” He mumbled, looking at Eraser.

 

The hero raised a brow before replacing him, getting close like the officer did.

 

It was almost unnoticeable at first, but if he listened, he could hear water. Like he was at a beach with waves calmly washing ashore. It was calm and peaceful. He swore he could smell the saltwater.

 

The nurse almost laughed at them. “Yeah, that's kinda the reaction we had. Never seen a quirk like it.”

 

“This teenager is strange indeed.” The Detective mumbled. 

 

“That is why we called for assistance.” She said, pressing a button on the bed. “Before you use your quirk, we will need to wait for the doctor.”

 

It went unsaid, but the implication was that if something went terribly wrong, more help would be needed to stabilize the kid. 

 

“We understand, it's not a problem at all.” The Detective agreed. “We actually-” A loud ringing cut through his sentence. It wasn’t the officer's usual ringtone.

 

Quickly, he fished his phone out of his coat and answered it. 

 

Aizawa couldn’t hear whatever was being said by the other person, but it was clear it was nothing good. Tsukauchi's eyes went wide, his fingers curling tightly around the device. 

 

After a few seconds, Tsukauchi replied before hanging up and shoving the phone back out of sight. “Alright, we are on our way. Do NOT engage without me present. Tell citizens to stay back.”

 

Eraser instantly grabbed his capture weapon. “A villain attack?” 

 

The Detective shook his head. “I don’t know for sure, but we need to go, right now.” 

 

“You don’t know?” Eraser asked, looking towards the boy resting in the bed. “That phone call sounded pretty damn important.”

 

“I’ll tell you on the way,” The Detective gritted his teeth, “but I need your help. I believe that they just found this boy's attacker.”