Rewind is the Quirk used by Eri.
Description#
Rewind grants the user the ability to reverse a living being's body back to a previous state.[1] It also gives the user a small, brown horn on the right side of their forehead, which grows larger when the Quirk is activated. The Quirk is the result of an extremely rare mutation, and bears no resemblance to any Quirk on either side of Eri's family's lineage.[2]
When Rewind is activated, Eri's horn grows and glows brightly. Those that are in contact or in the vicinity of Eri at the moment of the activation start having their bodies rewound to previous physical states, undoing or bringing back injuries or modifications from the present or the past. She is capable of reverting people back to a point before they even existed, effectively erasing them from existence.[2] Kai Chisaki even stated that this Quirk can rewind genetics, dubbing it a terrifying power.
During the climax of the Shie Hassaikai Raid, it is shown that Eri's strong emotions play a role in her Quirk's efficacy. Recalling how Mirio Togata risked everything to save her, a hope-infused Eri obtained the determination to help others, causing her Quirk to spontaneously activate, and immediately defuse Kai who had combined himself with Shin Nemoto. As Izuku Midoriya protected Eri, her Rewind remained active and continued to grow stronger, on which Izuku capitalized in order to activate Full Cowl - 100%. After the battle, Eri's Quirk began to run awry, with Eraser Head using his Erasure Quirk to neutralize her power, and eventually, her horn shrank back to its minuscule size.
Weaknesses#
At a young age, Eri was very inexperienced at using her Quirk and lacked any information about what it was due to Kai. She was also unable to control her Quirk, activating it by accident on occasion. The first instance of her Quirk manifesting caused Eri to accidentally rewind her father's age, erasing him from existence entirely when he held her.
Another time was when she was riding on Izuku's back while he was fighting Kai; she didn't know how to turn off her Quirk and Izuku only survived because he was damaging his own body faster than she could Rewind, and later after Eraser Head used his Erasure on her.
Rewind only affects living things, which made it difficult to train safely. These risks were mitigated by placing Eri in the care of Eraser Head, whose Erasure Quirk could neutralize Rewind should it go out of control. Rewind also only works if the user is within close range or making physical contact with the individual they want to rewind.
Rewind, as confirmed by Neito Monoma, requires the accumulation of an unknown energy in order to be activated, otherwise, the Quirk will remain dormant, with Eri's horn remaining small and stubby. She seemingly is only able to use it once in awhile as once its used the horn shrinks back down to a small stubby size.[3] It is unknown what exactly is needed to accumulate the "Rewind Energy".
Usage#
Through several tests and experiments, the Shie Hassaikai was able to develop a Drug that could target a person's Quirk Factor, rewinding it to a Quirkless state.[4] The Drug consists mostly of Eri's blood, cells, and flesh, which contain the properties of her Quirk. The organization created an antidote capable of restoring a destroyed Quirk using similar methods, though the antidote was never recovered.
Eri trained her Quirk through restoring the limbs of bugs and lizards, gaining some control over her power, being able to consciously activate it and not let it run awry. This degree of control was enough to restore Mirio's Permeation Quirk, which was erased by a Quirk-Destroying Bullet during the Shie Hassaikai Raid.
At some point, Kyudai Garaki was able to reverse-engineer the Quirk-Destroying Drug to focus on the effects of Rewind. During the Final War, All For One was able to use the modified drug to heal his fatal injuries and restore his body back to its prime. However, this version of the drug is a single-use only and All For One acknowledged that, with no way to stop it, he would eventually vanish from existence.[5]
In the aftermath of the Paranormal Liberation War, Eri had attempted to use her Quirk to heal Eraser Head's injuries, but did not have enough energy stored up to effectively do so.[6] During Izuku's final battle against "All For One", Eri cut off her horn and gave it to Eraser Head to use on Izuku to rewind his injuries. Due to the amount of energy she had stored up, he was able to rewind two to three minutes worth of time, regenerating his destroyed arms back.[7]
Eight years following the Final War, Eri's horn has grown back, although it is unknown whether her Quirk was temporarily or permanently damaged from removing it.[8]