Supposedly, Eri has a quirk, Rewind, that allows her to rewind an individual's body to a previous state. She used this, for example, to undo the damage Izuku did to his own body when he used One for All at 100%. Could Eri restore the One for All quirk to All Might and also cure him from his injuries done by All for One? Or are there any obstacles for something like this to happen?
That's a highly speculated topic in the fan base. Since we don't know much about both quirks, we can only judge from what we know.
Since Eri was able to restore wounds on Izuku, we can say that she can restore All Might's wound too. Eri can even rewind someone to their non-existence which, of course, means death.
We know that quirk bullets can make a person quirkless. It's also important to note that these bullets only change your quirk status, not the whole body.
Thus, you can assume that with experiments or by risking All Might, Eri can reverse him to a previous state where he is at his "might".
Now, these are my own thoughts. I think Eri can reverse All Might's quirk because of how One for All works. If a One for All user passes the quirk to someone else, what's left are just the embers. So, I think she can only restore those embers but not his power.
Eri's quirk is the most broken quirk we ever know. I think the mangaka knows this too so he won't use her because of this. It can destroy every buildup the manga has ever done.
From what I understand so far, Eri's quirk is capable of reversing an individuals body back to any point in time (from the individuals current state to any point before they existed). This means that she could ideally heal any person from any possible mortal damage because her ability can simply reverse the persons body back to a time before such an injury was sustained (just like she did with Midoriya Izuku). So its possible for her to heal the injuries that All might got from various villains.
The complicated part is If she can restore All might back to a time where he possessed One for all. Before I start with how that question can be answered, we need to understand the concept of paradoxes. Time moves linearly and is usually unchangeable, but in Eri's case, her ability affects time very subtly, Eri can take someones body back to any point before they were born, and in a way, that is a "time-related ability".
Usually, time related abilities cause a ripple effect which I personally named as "Time relapse" (the consequent result of an action due to its own distinct time difference). However, Eri's "Rewind" does not trigger a "Time relapse" and that either shows that:
(1) The complete nature of her quirk is still unknown Or (2) The mangaka has not completely thought up those aspects as of now. or (3) I'm just way overthinking things lol!
Paradoxes are logical possibilities which create apparent contradictions towards already known facts. I bring this up because All might has already passed the one for all ability to Midoriya, and so Midoriya is the current wielder of one for all. If Eri reversed All might's body back to a time where he has One for all then that would mean that there are 2 torch bearers of one for all. However, we already know that there can only be one wielder of One for all at any given time. This therby causes a paradox in that timeline and contradicts what we've already been told. Therefore it will be Impossible for her to take All might back to a time where he possessed One for All.
I don't know how paradoxes will be enforced in the "BNH Universe" but I'm guessing that no matter what she does, there will be "some force" preventing her from restoring One for All back to All might.
Eri's Rewind Quirk attracts so many possibilities and paradoxes that conflict with the overall logic of the anime as a whole. However, that is the route the Mangaka chose because her name itself ("壊" + "理") means to "break reason".
A bit older post, but I see a lot of confusion! Let me clarify!
- There is no proof of time manipulation by ERI. She is just changing the state of a system, or material, to a previous condition without affecting time.
- ERI can specifically target her power. While healing Deku, she doesn't reverse his memories at all, thus she doesn't reverse his entire body, only the damaged parts. This is extremely important!
- One For All is not part of the body! It is an entity of power used by one individual at one time! While there is a genetic marker used to transfer this power, anyone could steal it at any point if it was just a DNA thing. I strongly believe that the process was only like a contract to pass the torch. If it was the users body that was actually producing the power, it wouldn't have dealt so much damage to it.
- ERI could heal Allmight's wounds for sure and it might happen, without affecting his memories. There is no reason why she couldn't do that, considering what she has done already.
- Considering point 3, Eri should not be able to give Allmight his power back, but there could be a workaround for one final fight considering the 'remnant' power that is left in Allmight after he passes the torch.
- Giving Allmight his power back would create a lot of problems for the story and it's development. It is that simple... Allmight at full power would fix all of the problems on his own again ... Then Deku and everyone else would be worthless.
- Allmight is more of a mistery than ERI! Why can he transform? Why does he look different in Dekus conversations with the previous owners? Why was he able to suddenly master such a massive power?
Just to clarify the paradox thing, just because she reverts someone's body back to a previous version of their timeline or out of existence entirely, this does not equate to any form of timeline manipulation. The person's body may revert, but it doesn't remove that person from the past.
However, the obvious thing is, if her powers were true to the way they work, when she healed Midoriya since his injuries reverted to before they happen, his memories should follow suit and thus he shouldn't have remembered breaking his body. Likewise, if it was used on All Might:
- Not only would All Might be healed, but he would also regain his quirk, and because this does not affect the timeline, it would not remove Midoriya's quirk either (because quirks are based on genetics i.e. two parents with different quirks produce offspring with one or both or a combination, thereof both quirks such as Endeavor's son with both fire and ice from his mom), thus the quirk One For All must be transferred through a change in DNA by our current understanding.
- All Might would also not remember anything from the point of which he was terminally injured forward to the present, literally erasing his memory of Izuku and his transfer of the One For All quirk to begin with. (Bonus thought: this would mean All Might and Izuku would have One For All at the same time)
Personally, I think the only thing her quirk does in regards to "erasing" another person's quirk is to revert it to it's dormant state before it activated. I think that realistically after a maximum of 4 years the person's quirk will reactivate. Obviously we haven't seen enough time to pass to see this happen, but it makes the most sense to me.
The problem is how Eri's quirk is perceived.
It is called Rewind and it is assumed to have not been thought out as she 'rewound' her father thus broken as she should not exist since he never existed.
I believe the actual power of her quirk isn't essentially rewind but restore. Eri can restore someone's body to any point in their life without it affecting time. For example, she restores Deku during his fight with Overhaul, if she rewound time, he would be rewound to a version that was prior to combat thus defenceless each time as he wouldn't even know what had happened between the moment she choose to rewind him to and the current moment.
I think she can restore people to the earliest possible version (which would be the moment the egg is fertilised in the womb) this would mean she didn't rewind time but restored her father to an near-on invisible particle (which obviously would cause him to die) but wouldn't affect time or her own existence as he did exist up until that moment.
If the restore theory is correct, the reason why her blood can be used to stop quirks is that it can be used to restore an individuals quirk back to before they were able to harness it. It is said that a quirk appears at around the age of 4, if it was restored to before this age it would cause the hero to stop being able to use it.
I think her quirk would allow her to restore Almight back to him at his peak physical condition but it wouldn't be able to restore his power. One for All wasn't a quirk he was born with as he was quirkless and the power is more something that is loaned to a hero rather than something that is theirs.
"One for All" is a created quirk by "All for One" for his brother. It is unique in the world of My Hero Academia due to this. It is passed from individual to individual because it is "man-made" and not naturally occurring. At this point, there is only one instance of it in existence, but "All for One" could (in theory) recreate it in its base form at least.
If Eri were to revert All Might to a time where he had the quirk, there could be two people with "One for All". Since it is a created quirk in the first place, it could be duplicated.
I think the main problem is the fact you need to look at this time thing in many ways. A quirk works in many different ways, and so does time travel.
Eri’s quirk can control the time of someone’s body, which allows her to use her quirk without affecting the time stream. Of course, if she can get rid of a quirk, she’s using her quirk on another scale. She can use her quirk to not only reverse one person's body/other stuff, but as well as the human's evolutionary state.
For example, she could go to a person, and in theory, turn them into apes, from which we have evolved from. As for All Might's quirk, he won’t be able to give that back because that was something much different. Of course, Deku could always give it back, but I think Eri’s ability follow different strands of time, but she would most likely be able to heal the damage all might got.
One For All wasn't known for sure to be created by All For One. He passed an ability to stockpile power to his brother. They specifically state that it is unknown whether he did this, knowing of his brother's prior ability, or simply to try and make him stronger.
One For All is passed from individual to individual because the brother who was given this ability to stockpile power already had a quirk that allowed him to pass on quirks to others. A quirk that would have been useless and gone unknown if not given another power to actually pass. The fact that it stockpiles essentially means it can continue to gain power endlessly from owner to owner.
Being that it's a passed quirk and not one granted through birth, I don't think it makes sense to be able to revert All Might back into having One For All. it's One For All, not All for All. All For One doesn't create quirks, he steals them. The only way he "creates" a quirk is by combining the powers of the ones he's stolen to use himself or implant Nomus with multiple stolen quirks to enhance them.
Eri also can't control her power, so perhaps they can heal his stomach, but Overhaul already said the only way to stop her is by killing her and bringing her back, maybe knocking her out with that X-rated heroes scent or mind-controlling her to stop? Though, I assume Overhaul would've tried most techniques as he said he spent years testing.
After starting the story from the beginning again, I've come to the conclusion that, while what you are saying might be possible... the most likely outcome is that All For One steals her quirk and restores All For One to his prime. I know he meant to pass things on to Tomura, but I just find it highly unlikely that Deku will never fight a full-powered All For One.
Many people pretend that her ability has anything to do with manipulating time. Her power is to rewind a body to a previous state, this does not create a paradox. Her ability to rewind her father to a point of nothingness does not at all create a paradox with her still living because she’s not time traveling.
Whether or not she could give All Might One For All back, I have no idea, would assume yes, would also assume she could push Deku back to a point where he no longer has One For All, essentially erasing the quirk from existence.
Lemillion is hinted at being able to get his quirk back, so why wouldn’t All Might? Would also understand that her quirk sends a person's ability with their quirk back to when they were an infant and don’t have full control of it. An example of a person's quirk noticeably developing throughout the show is the hardening guy.