Izuku couldn't sleep. How could he? The comet that was supposed to pass by ten years from now had made an early appearance, one that only happened every hundred years. It made him remember things he apparently forgot. That Kacchan had been a part of One For All even after that timeline had passed. That Izuku was able to connect to Tenko on a level that should've only been possible if he possessed All For One. His whole theory about a linear time loop, however crazy it sounded, suddenly gained a lot more evidence.

It already had a solid base, namely Kacchan's essence within the quirk. A part Izuku had forgotten about over the course of time during their many failed attempts at reversing this loop. It was a link to their original timeline, something that hadn't happened at the time when he dreamed about it. Then there was Tenko, who'd reacted to Nana during the second timeline. That shouldn't have been possible, either. Not without some sort of connection allowing their minds to mingle. Something like One For All and All For One.

And now the comet... The very same one Izuku saw in his first life, now passing by way too early. It made him wonder whether the comet had passed by in other timelines, too, but that he simply hadn't noticed, too busy trying to fix things to look at what was happening around him. How many years had passed since it all started? Izuku wasn't sure... He'd died before the loop was finished often enough that his experience itself wasn't enough to take everything into account. But it was enough to validate one thing, to be certain of something he wasn't sure about before.

This wasn't time travel.

This time loop wasn't a loop at all. It was sequential, linear. Not everything got rewinded, not fully. So that must mean there were other sorts of quirks in the mix. Illusions, memory alteration, maybe also hallucinogenic ones, Izuku wasn't sure. It would explain why they were never able to figure out how Jikan's machine works. It wasn't a time machine, nor a perfect rewind machine. It was something else, some sort of hybrid of dreams and reality. Which meant that everything here, everything he experienced, was based on the one true timeline. The real timeline.

It would explain why everything seemed to warp towards the given path. Why there was something akin to fate keeping everything together, setting certain experiences in stone while others were far more fluid. It meant reality as he once knew it still existed, buried underneath all of these tricks and lies. But even so, years upon years had passed. And so the time Izuku so desired to return to had passed with it. Gone forever more. Which made him wonder what their current reality looked like without the influence of Jikan's fucked up machine. I mean, in normal circumstances, they would've all died a long time ago, right? So rewind must affect their bodies more than anything.

What about their minds, though? Sure, their memories got altered, but that quirk was easily penetrable in the right circumstances. It mustn't be as strong as rewind, then. Which made him wonder why they didn't use rewind for everything? Maybe that wasn't logistically possible? Maybe time travel was still a fever dream, after all. Kacchan shifted next to him, making Izuku look over. Yeah, he could bring back Kacchan's memories right here, right now. Undo the effects of whatever quirk they were under by simply telling him to jump off a roof and pray for a quirk-

Wait.

Quirks.

Jikan's goal was to restore All Might to greatness, right? And by rewinding their bodies, it was only logical for him to regain his strength and power, but what about his quirk..? One For All couldn't be transferred without the specific intent to do so, and Izuku had never- God, this idea was stupid and reckless and had absolutely no foundation whatsoever but- He glanced aside at Kacchan again, who was deep asleep. It was probably nothing. This was all just some stupid hypothesis, but Izuku was going to drive himself insane if he didn't at least try. A few minutes later, he was standing by the cliffside, shivering as a cold breeze made its way underneath his clothes.

"This isn't even gonna work," he mumbled to himself as he took a deep breath. Focus. A one track mind. He got this. He knew how to do this, how to activate it, how to maintain the power surge. And yet, nothing seemed to happen. "Ha, I knew it. This was a stupid idea to-"

He cut himself off, his breath hitching as his heart clenched. A sudden flash of green invading his vision as he lurched forward. Before he realized it, he was heaving, his hands firmly clenching the grass underneath his palms as his body shook. Small green sparks danced around his skin, lighting up his body and everything around it. It was unmistakable, and yet Izuku was still in denial, his mind reeling as he tried to gain control over his body. But he couldn't move, couldn't deal with the sudden pressure this power created, as if he was back to square one.

But it was there. One For All was there, within him, showing itself.

He took a shaky breath, allowing the quirk to dissipate as his body collapsed onto the cold damp grass. God, that was exhausting. Seems like One For All took a big toll on his body as of now. Izuku did have less muscle mass than before, so guess that was a factor he should take into account. Still, at such a low percentage he should at least be able to move somewhat, right? Hmm, maybe the quirk evolved more than he thought it did... If he really had One For All all these years, the stockpiling effect would be-

"Glad to see you finally understand."

Izuku blinked, suddenly surrounded by low hanging mist. The atmosphere had shifted and he realized that he must've fallen asleep, because he was no longer lying on the cliffside but rather within One For All. He crawled up, seeing a familiar room in front of him. A half circle of chairs, each in use by one of the previous holders. Yoichi sat in the middle, flanked by both Second and Third. The vestiges trickled down from there, the edges being occupied by Nana and- Izuku's eyes widened when he saw Nana wasn't at the end anymore, unlike All Might. No, instead of her it was-

"Kacchan..."

It was really him. His body was fully formed, sporting his signature orange as his soul was wrapped inside his hero suit. He wasn't wearing the mask, nor the gauntlets, but everything else seemed to match.

"Took your sweet time getting here, Deku," he grunted, leaning on his hand as he looked away.

"Katsuki has been trying to reach you for quite some time now," Nana explained. "He seemed to be the only one who could penetrate your dreams."

He's been infiltrating his dreams? Trying to get him to accept One For All-

"Please let me stand by your side, Izuku. Don't leave me behind, don't reject me. I can help you- We can help you. We'll face this together, we'll give you our strength and-"

Oh god, that wasn't just dream Kacchan talking about letting people in, was it? That was this Kacchan, his essence within One For All desperately calling out to him. After Izuku told him he'd be better off without it...

"Ya pissed him off," Lariat laughed, seemingly finding this all pretty amusing. "Tenth is right though! Took ya long enough!"

"I don't... I don't understand," Izuku stammered, glancing around at the vestiges. "I thought... Our memories, they..."

"We've been able to see through this ruse for quite some time now," Yoice stated. "At first the memory alteration affected us as well, but as One For All increased in power, we became more self aware. It also allowed the small essence of the tenth to take form in a way that shouldn't have been possible."

"Not unless you cultivated and stockpiled for decades," Second added. "But somehow, Katsuki has been able to integrate himself seamlessly."

"Don't act like you're annoyed by that," Kacchan snapped. "I know you're fucking delighted to have one of your decandents inherit this quirk."

"What?" Izuku asked, confused and surprised, while Second scolded Kacchan for his language.

"We talk, Izuku," Katsuki snapped, as if that explained what he just said. "These guys may have been dormant for ages, but they've been yapping my head off all the same."

"Awe, you love us," Nana teased, leaning over to pinch his cheeks. They continued to squabble while Izuku put his focus on Yoichi, knowing he would be the one providing answers.

"One For All is a quirk of the mind," he told him. "When you thought you were quirkless, it caused some sort of mental blockade. We weren't able to manifest or give you any of our power, so it stayed stockpiled within this space, unable to be released."

"If it wasn't for Katsuki absorbing most of it in order to form and gain strength, I'm sure your body would've exploded long ago," En added, making a shiver run down his spine at the mental image. But wait, if Kacchan had been fully integrated within One For All, did that mean that Izuku could use his quirk..? That was something he had to test out later. For now, he had to focus on this- Whatever this was.

"So it's as I thought, it's not a true rewind machine," Izuku breathed. "Time is linear, and so is this loop- this illusion. But how do we break it?"

"We don't hold the answers you're looking for," Third told him. "But we'll stand by your side and help you figure it out. That is, if you let us."

"Of course," Izuku smiled, seeing the fight between Nana and Katsuki ended with the woman holding him in a headlock as Kacchan struggled and complained. "I won't reject you, not ever again."

//\\
\\//

Katsuki yawned as he rolled up his sleeping bag, seemingly more tired than Izuku. It was a good thing the green head had woken up before anyone else so that he'd been able to crawl back into the tent without arousing any suspicion. Still, quirk dreams always left him restless in a way normal dreams didn't. Probably because his mind was still so active whenever he was inside One For All. It didn't get proper time to rest and recalibrate like the rest of his body.

"Didn't sleep well?" Izuku asked as Kacchan rubbed his eye.

"No, that's not it," he grumbled. "Just...odd dream, I guess."

He glanced at Izuku, momentarily squinting his eyes, as if Izuku was the reason he was tired.

"You're fucking loud."

"Hah?" Izuku asked, raising an eyebrow. "Wait, are you accusing me of snoring? I don't snore, Kacchan!"

Besides, he was lying outside most of the night so there was no way he was keeping him up even if he did snore. Which he didn't.

"That's not it!" he complained, angrily pushing his sleeping bag in the hose, giving up on rolling it up somewhat decently. "Your mind is just so damn loud, I don't know! It doesn't make any fucking sense."

But it did make sense, didn't it..? Izuku remembered how All Might had once told him he could sense the vestiges talking to him when he was unconscious. He had to touch Izuku to feel it, and he couldn't make out what they were talking about. He just felt they were communicating with each other, that Izuku's mind was wrapped up in the quirk. The connection had never been the same as the connection All For One and Shigaraki shared, but it ran deep nonetheless. Maybe that's why Kacchan had been able to sense something, too? Because a part of him had been integrated within OFA, because he was able to sense it?

Time was linear, after all, so he was technically a past user, even if he didn't know it. It was a possibility Izuku hadn't stopped to consider. But if Kacchan was truly connected to him that way, if he could really sense One For All within him... This could pose some problems along the line if Izuku wasn't careful. Katsuki could find out he wasn't actually quirkless, could start to question him, could maybe even accuse him of working for All For One again- No, Izuku wouldn't let it come that far.

"Sounds odd, indeed," Izuku hummed. "I didn't sleep all that well either, to be honest. Still uh filled with the jitters after yesterday..."

Both their faces flushed at that, and Katsuki choked out a small sound of agreement. They were together now. Boyfriends. Once again, in Izuku's case. They really had an on-off thing going, hadn't they? Since the loop was linear and all... It was better not to think about it.

"So? You boys had fun?" Masaru asked as they started breaking down the tents. "Did everything you wanted to do?"

Izuku could tell that last question was directed to Katsuki more so than the both of them. Had Kacchan told them what he was planning? Cute.

"Yeah," Katsuki grunted as he worked, feeling Masaru's eyes on his back. "Shut up and work, old man!"

Izuku chuckled, finding flustered Kacchan more amusing than anything.

"We had a great time, uncle Masaru," Izuku smiled. "Thanks for taking me along."

"The pleasure was all ours, Izuku."