Izuku realised that he didn't know a lot about One for All.

It's a power older than Hero society as a whole, created during the first years of the Quirk crisis. It's nine generations of power in a world of fourth-generation Quirks, so he should have known that it wouldn't behave like other Quirks.

He stumbled as he ran along the training ground, Full Cowling sputtering in and out of existence as he tried to chase after Iida, who was his opponent for the combat drill Mr Aizawa had them doing.

After a few moments, he gave up chasing Iida as the fluctuating power levels of his Full Cowling made it impossible to move without falling over. He sat on the ground and made the official UA gesture for 'I need help but I can't move.'

Not many people knew about it because it was in the second half of the student handbook, but Izuku had read it extensively. Apparently, so had Iida, who skidded to a stop next to him. "Midoriya! Is everything all right? What's the issue?"

Izuku rubbed the back of his head, fumbling over his words a bit. "I'm sorry, but my Quirk won't listen to me. It's shifting back and forth through my safe levels of usage. I can barely move like this, let alone fight."

A few moments later, Aizawa landed a few feet away, rolling to stop his momentum as his scarf retracted back around his neck. His eyes flashed red and Izuku felt One for All settle underneath his skin. "Thank you, sir. I lost control and was worried that it might go over my safe limit."

Aizawa frowned, looking him up and down. "Fine. Iida wins this match by default. Come with me, both of you. Midoriya, you'll be going straight to Recovery Girl."

Izuku winced and hung his head, nodding. "Yes sir. Sorry to cause you trouble."

Aizawa shook his head. "It's fine, Problem Child. Do you have any idea what might have caused this loss of control? You normally have a pretty good hold on it nowadays."

Izuku hummed, holding his finger around his chin. "I'm not sure. I didn't feel anything weird before now, and Full Cowling has never acted like this before. Maybe because I finally reached 8% it's harder to control? That wouldn't make much sense though; it's only 3% higher than my regular level…"

Izuku flinched as Aizawa's hand landed on his shoulder. Aizawa seemed to notice and took his hand off, pocketing it. "All right, I get the picture. You don't know. Try and get it sorted before tomorrow, but if it still doesn't respond to you by then, notify me or Nezu and I'll see about getting you dispensation for drills and activities for the moment."

Izuku perked up at that, a panicked look on his face. "No! I'll be fine, sir. I'm sure that it will be working for me properly after a good night's sleep, maybe a nice meal. I won't have to miss out on any more classes!"

Aizawa glanced over Izuku to see Iida frowning beside them. "Problem Child, not blowing up your limbs because of this is the most important thing right now. Remember what Recovery Girl said about what future damage could do to your arms?"

Izuku froze at that, and Aizawa knew he had at least made the kid think about what would happen if he kept going like this. For all Aizawa knew, he would do it anyway, but for now, he had until at least tomorrow to figure out what was going on.

"Mr Aizawa! Deku! What happened! You just sat down in the middle of the field! Are you all right? Yaomomo said that you were in trouble!"

Izuku blushed as Uraraka dove into his personal space, looking him over for injuries. "It's fine, Uraraka! I was just having some issues controlling my Quirk; I'm sure it will be fine soon."

Uraraka didn't let up though, not budging on making sure he was all right, as did Tsu and Todoroki. At some point or another, Izuku's eyes met Bakugou's, and he heard the boy let out a 'tch' and walk off towards Kirishima.

After explaining to his friends that he would (probably) be ok, Aizawa sent him off to Recovery Girl with Uraraka to escort him. That last bit wasn't actually part of his wording, but the girl floated Izuku anyway and dragged him along.

"It's to make sure you don't break your legs accidentally or something! Just stay still and let me do this for you, Deku!"

Izuku took her words to heart and stayed as still as possible as she dragged him along behind her. They had almost reached Recovery Girls office when his phone dinged, a notification from his news app showing up.

THE SHADOW OF MUSTAFU: A NEW VIGILANTE? RECENTLY CAPTURED VILLAINS SAY YES!

Izuku whistled as he saw the headline. That was the area around UA! While he didn't support breaking the anti-quirk laws (in public), he couldn't help but respect someone doing good and helping people even at the risk of getting in trouble.

"What's that, Deku?"

Izuku yelped, almost dropping his phone as Uraraka spoke up. "Oh! It's just an article about a new vigilante around here. The police think they have some sort of 'darkness' Quirk because some villains said they were attacked by someone who looked like 'the night sky itself if it was angry.'"

Urarka laughed. "Ha! That sounds like a quote out of a comic book!"

Izuku chuckled as well, nodding. "It does, yea. But then again, we are at a superhero school, so we probably shouldn't say anything."

Uraraka turned to him as they reached Recovery Girls office, a soft smile on her face as she dragged him down to her eye level. "I guess that's true, huh. Good point, Deku!"

Izuku was about to respond to her when the door slammed open. He twisted around to find Recovery Girl staring up at the two of them.

"Oh for fucks' sake, Midoriya, this is the third time this week."

"No broken bones, no torn muscles, and nothing that would suggest someone using a Quirk on you. You're in peak health, Midoriya."

Izuku frowned. "That's really weird. So there's really nothing that can tell you why my Quirk would have lost control like that?"

Recovery Girl shook her head. "None at all. According to this, the only thing wrong with you is the misaligned joints on your right hand and the scar you have on your tricep."

Izuku nodded, standing up. Recovery Girl hoped that he could at least feel better knowing that he was ok. And after all the time he had spent sitting on the bed letting Recovery Girl do tests, his Quirk had calmed down.

"So I should be fine to walk back to the dorms, then?"

Recovery Girl sighed, hopping down from her chair. "Unless that girl outside wants to give you another lift with her Quirk, you should be fine to walk back. Just make sure you change out of your costume first."

Izuku smiled, hopping up and down on each foot. "Thank you, Recovery Girl! I don't know what I'd do without you."

Waving him off, Recovery Girl shook her head, sitting in her desk chair. "Probably be in the ICU in some mental hospital because of your stubbornness. Now get out of here, I have work to do."

Izuku sputtered out some apologies for bothering her and darted out of the room, and Recovery Girl heard the girl's voice from before, and then a hand hitting cloth as Midoriya yelped.

Turning her head, she saw the girl dragging Midoriya through the air again, shaking her head, a sigh escaping her. Recovery Girl laughed to herself for a bit.

'At least he'll have more support than Toshinori did.'

10:00 pm. His bedtime. Thank god.

As Izuku put his schoolwork away and laid down on his bed, he closed his eyes, only to open them a moment later when he heard someone talking, but it sounded really far away.

Looking in front of him, he yelped as he saw himself in a black void with the silhouettes he had seen at the sports festival standing around him. Looking down, he saw that he was also a silhouette.

One of the figures walked up to him, waving their hand in front of his face. Izuku turned to them and tilted his head, hearing the slightest whisper in the distance. Was this person trying to talk to him?

"I can't hear you, I'm sorry"

He knew that he had spoken, but his words were muted, unable to be heard even by himself. The figures seemed to hear him though, as the one in front of him seemed to nod. Izuku saw their chin seem to move, and he was able to just barely pick up on what they were saying.

Wake up

Something has changed

Izuku nodded, standing up and pinching himself, yelling as loud as he could, doing everything he could think of to try and wake up. But he felt something grounding him here, blocking him from waking up.

He stayed in the void for at least half an hour, maybe more, before he suddenly found the blockage stopping him from leaving gone. With a start, he hit the floor beside his bed as his eyes flung open.

Full Cowling surrounded his body, so he didn't actually feel the soft impact, but his heart was still thumping. Checking the clock on his bedside table, he saw that it was exactly 5:30 am. As his eyes hit his clock, the alarm went off.

He slowly rose to his feet, his eye wide and his heart racing as his Full Cowling surrounded him at just above his upper limit. Had he used One for All in his sleep? If it was from muscle memory or a nightmare, why was it only just above his upper limit?

What the hell was going on?

B+ RANK VILLAIN "REAPER" CLAIMS TO HAVE BEEN CAUGHT BY THE SHADOW OF MUSTAFU!

Izuku hummed to himself as he waited for All Might to show up for a talk. He had texted the man straight away after he had woken up to hopefully figure out what was going on, but he hadn't arrived just yet, so Izuku was checking the news.

He had had a bit of respect before, but now he was just downright impressed. "Reaper" was a notorious villain with the capability to make people see their worst fears if you looked into his eyes, locking people in place.

For a newly discovered vigilante to have defeated them, they either needed to have had the perfect counter Quirk or be skilled and brave enough to fight the villain even under the effects of his Quirk.

"Young Midoriya! I am here!"

Izuku smiled as All Might entered the little meeting room he had asked him to come to. "All Might! I'm glad you're here. I'm having some issues with One for All."

All Might's smiled turned into a frown, and he deflated back into his thin form, coughing up a small amount of blood. "That's quite troubling. Aizawa told me that your Quirk was acting up yesterday, so I'm assuming something happened this morning?"

Izuku nodded. "Yes sir, I had a... dream, I think. And I'm still a little rattled from it."

Toshinori hummed, tapping his chin. "A dream? What about? I've had some dreams about One for All before, but they've always been vague and hard to remember."

Izuku took a deep breath and spoke. "I was in a black void, unable to really move, surrounded by those silhouettes I saw during my fight with Shinso at the sports festival. I think they were trying to talk to me. They said that I had to wake up, that something had changed. But when I tried to wake up, I could feel something… holding me where I was. As if I was being blocked from waking up by something."

Shaking his head, he looked back up, making eye contact with All Might. "I don't know exactly how long I was like that, but eventually, whatever was holding me there dispersed, and I woke up a few seconds before my workout alarm went off. Full Cowling was activated as well."

All Might's face was scrunched up, obviously a little worried about what he had said. Panicking slightly, Izuku waved his hands around. "But I'm fine now! I promise! It was just a little scary being trapped like that. I'm good now."

That just made his mentor's frown deepen for a moment before his face softened. "Of course you are, my boy. I trust you. Have you seen Recovery Girl about this just yet?"

Izuku shook his head. "No sir. I went to her yesterday about One for All not listening to me, but she said that there was no physical reason that it should be malfunctioning, at least that she could see. I don't want to bother her with this so soon after wasting her time."

"You aren't wasting anyone's time, Young Midoriya. You are having a potentially dangerous issue with your Quirk; that is something worth looking after for a few days. You are worth looking after."

Izuku froze for a second before dropping his shoulders. "Of course sir, I'll make sure to speak with her later today. I don't think Aizawa is going to let me participate in today's drills anyway, so I can see her during hero basic training."

All Might smiled, his hand reaching the top of Izuku's head as he ruffled the boy's hair. "An excellent plan, my boy. Now, how about we go get some good ol' fashioned American breakfast. Nothing's better for bad dreams than bacon & eggs!"

Izuku almost piped up about how he couldn't break his diet, but as All Might dragged him out of the building (an overstatement, his thin body could barely pull himself along) Izuku stopped himself.

He could see the bright smile on All Might's face as he talked about a breakfast meal he once had, and he had to admit that bacon and eggs did sound pretty delicious.

"I think the best plan of action right now is for you to try and stay up a little later than usual."

Izuku tilted his head to the side, confused. Recovery Girl wanted him to stay up late? "Isn't that like, the opposite of what I should be doing to stay as healthy as possible?"

Recovery Girl tapped his leg with her staff softly, and Izuku rubbed the back of his head. "Sorry for interrupting."

Recovery Girl waved him off, shaking her head. "Pah, don't worry. And normally, yes, you should have a consistent sleep schedule, but think about it this way.

"Your Quirk suddenly stops listening to your commands, you start having weird vision dreams, and you find yourself trapped in this dream for an extended period. Something probably happened during your sleep."

Standing up, Recovery Girl walked over to her cabinet and pulled out a small sheet of foil. "Staying up will help us figure out if it's a One for All thing, or if you've been affected by another Quirk. I want you to take these at around 6:30 pm tonight. They should keep you awake and alert until around midnight."

Izuku's eyes widened. "Midnight? But I have to be up by 5:30 in the morning to do my exercises!"

Recovery Girl lifted her staff again, and Izuku shut up. "No, you do not. I am officially clearing you from working yourself too hard until we figure out what is happening to your Quirk. That means no access to the gym, and no hero classes until we figure this out."

Izuku opened his mouth, about to argue, but Recovery Girl interrupted him. "This is not a punishment of any kind, young man. Lord knows you've injured yourself enough to earn my anger, but this is truly for your own safety. With a Quirk as powerful as yours, we can take no chances."

Izuku dropped his shoulders, sighing. "Yes ma'am. I'll do what you say. Thank you for your help."

Recovery Girl nodded, smiling softly. "Good. Now get out of here, Kiddo. I'm sure you wanna watch your classmates brutalise each other for sport."

Izuku chuckled and stood up, waving goodbye as he exited the office. He looked down at the sheet of pills in his hand, still a little iffy on Recovery Girl's plan.

'Guess today is going to be a really long day, huh?'

Izuku huffed as he popped the two pills Recovery Girl had given him out of the little sheet of foil.

Did he really need these? Surely he could just… no, Recovery Girl had given him clear medical instructions. He had to do this. Checking the clock again, he saw that it had ticked over to 6:31 while he stared at the pills.

Chucking them into his mouth, Izuku downed the entirety of his water bottle. He hopped up and down and jogged in place for a little while, trying to speed up his digestion, and about ten minutes after he had swallowed the pill, he suddenly became extremely alert.

Izuku shook himself, tapping the power button for his computer as he bounced up and down. If he was going to be awake for tonight, then he was going to get lots of work done, or at the very least he was going to go down an interesting rabbit hole of research.

Honestly, the rabbit hole was more likely.

10:28 pm.

Two minutes before the approximate time he usually fell into REM sleep, according to the health monitoring watch he had gotten as a gift from Melissa. He hummed along to some music playing from his phone, the theme song to an old All Might tv show, and clicked on a link to a website that apparently had pictures of Endeavour smiling.

He didn't particularly like the man—ok, that was an understatement—but seeing a picture of Endeavour smiling was a rare thing for any hero fan to see. The page had just loaded up when he suddenly lurched out of his seat.

"What?!"

His eyes darted back to his clock, showing the time as 10:30. He would normally be sleeping like a baby right now. Did whatever was happening to him wait until then to affect him?

He tried to reach out for his phone, but his arms felt like they were yanked back to his side as he was made to walk over to the sliding door out to the balcony, his hands opening it up without him saying to. But now that he was in the light of the moon, he could see something.

Strands of pitch-black seemed to run all over his body, flexing and relaxing like muscles of their own as they dragged his limbs around. Whatever was controlling his body swung the door open, and Izuku stepped out onto the balcony against his will, his hand landing on the railing.

"HELP! MR. AIZAWA! ALL MIGHT!"

Izuku yelled out, and he heard something crash in Minetas room, the sliding door ripping open as Izuku's feet landed on the railing of the balcony. "Midoriya! Are you all right?!"

"Mineta! Go get Mr Aizawa! I can't control my bodeeeeeeee!"

Izuku's sentence was cut off as whatever was controlling him made his body leap off his balcony. Izuku saw the ground rushing towards him and screamed, but before he hit the ground, he felt gravity leave him.

"Urara... ka?"

Looking around him, he couldn't see Uraraka anywhere. So how was he floating? Whatever was controlling his body directed him to the ground, and Izuku yelped as the black strands covering his body grew, hiding more of his skin from view.

His entire body was covered in the black now, and Izuku was about to yell out for Aizawa, or Mineta, or Uraraka, or anyone, when a black strand covered up his mouth, essentially gagging him.

Full Cowling was switched on, and his body darted out towards UA's front gate at the height of his safe limit, around 10%. Except unlike normally, Izuku's eyes weren't catching up to his speed.

And after a moment, his vision turned black as whatever was controlling him covered his eyes. He felt his alertness leave him, and his eyes shut on their own.

And then he was back in the void again. But instead of the friendly vestiges, there was a ball of light, brighter than the sun itself and made up of eight distinct colours. It felt alien and very powerful.

And it felt… curious?