One For All

**One For All** is the transferable Quirk that is possessed by its ninth and current host, Izuku Midoriya.

In the past, it was originally used by Yoichi Shigaraki, and later, its other previous hosts: two unnamed users, Hikage Shinomori, Daigoro Banjo, En, Nana Shimura, and All Might. It was also briefly used by Katsuki Bakugo.

## History

Long ago, All For One, a man with a Quirk that allows him to steal other people's Quirks and transfer them to others, forced a Quirk on his seemingly Quirkless younger brother, Yoichi. This Quirk allowed him to stockpile power within his body. However, unbeknownst to either one of them, Yoichi already had a Quirk with no other power than that it could be transferred to another person. The transference Quirk and the power stockpiling Quirk merged to form One For All.

After discovering this about his newly developed power, due to his strong sense of justice, Yoichi tried to defeat All For One, but given the huge difference in their strength, he failed. He decided to entrust the Quirk to future generations of Heroes, hoping that they would be able to cultivate One For All and one day put a stop to All For One. He passed it on to the Second User, a resistance leader who had freed him from the prison cell where his brother was keeping him.

All For One sought out One For All and as a result, almost all of the users of One For All fought him and were killed by his hand, but not before they each had the chance to pass on the Quirk to a successor so that it could reach the future and elude the Villain. The fourth user, Hikage, believed that he would not be able to defeat All For One and decided to use his "turn" with One For All to seclude himself and train the Quirk to be as strong as possible. However, after eighteen years, his body unexpectedly started to deteriorate. Though he blamed it on an unknown disease at the time, in reality, possessing One For All and his original Quirk had dramatically shortened his lifespan, forcing him to pass it on shortly before dying. All For One attempted to steal One For All twice, first from the fifth user, Daigoro, and then from the sixth, En, but had failed both times. This was apparently because he wasn't able to muster the rage to overcome the fragments of the wielders' consciousness.

The seventh user, Nana, was the last holder killed by his hand, while her apprentice and heir to One For All, Toshinori, fought All For One twice, winning both battles, but suffering significant injuries in the process. Despite his injuries, and despite the pleading of his friend/sidekick, Sir Nighteye, he continued fighting for another six years before picking a successor. This would take him to a total of 40 years as One For All's wielder.

After much deliberation of choosing a successor, and shortly before he was scheduled to begin teaching at U.A. in order to help him find one, he encounters Izuku, a Quirkless boy just like he was. Impressed with Izuku's drive to become a hero, and with his selfless spirit, he chooses him to become the ninth and current wielder.

While the Quirk was initially perceived as primarily a source of tremendous power, things started to change as Izuku became more accustomed to the Quirk, and it reached the "point of singularity". Not only did the consciousnesses of the previous users gain a more physical form within a vestige realm that could communicate with each other and Izuku, when prior they were only echoes seen in dreams, but also the Quirks of the predecessor's emerged from One For All's core, allowing Izuku to use them.

This sudden growth led to Toshinori conducting research on the past of the users in order to find any information to aid Izuku. It was here when he discovered the autopsy behind Hikage's death, and while he was unsure about it at the time, Toshinori speculated that he'd been able to continue using One For All for so long because, unlike most of its other wielders, he was Quirkless.

Due to this revelation, according to Yoichi, Izuku might be the last user of One For All, as it can only be handled by someone who was originally Quirkless, and considering said population has greatly decreased through the generations. The Quirk has been passed down through nine generations, growing stronger with the passage of time. Currently, One For All is one of the most powerful Quirks in existence, however, it proves very difficult to fully master.

In order to steal One For All, All For One decided he needed someone with extreme malicious intent, powerful enough to overpower the will of both the wielder and the other consciousnesses within One For All. For that purpose, he groomed Tomura Shigaraki and filled him with hatred. Then, All For One transplanted his original Quirk onto Tomura, and seized control of the younger villain. Using Tomura's will, All For One attempted to steal One For All from Izuku, but was thwarted by Yoichi and Nana. Knowing that Tomura's body was still incomplete, All For One retreated and began to wait for its completion.

Very few were informed of One For All's true nature, for fear of what villains would do if they found out that the world's most powerful Quirk could be transferred, as well as discourse among fellow heroes and the general public. Prior to the start of the series, other than the users, All For One, and his confidant Kyudai Garaki, the only known people who knew the truth were Nana's partner Gran Torino, Toshinori's sidekick Sir Nighteye, U.A. staff Principal Nezu and Recovery Girl, and police detective Naomasa Tsukauchi. After Izuku nearly gave away the secret to Katsuki Bakugo out of guilt, the latter managed to deduce most of the truth, with the rest explained to him by Toshinori.

However, after the Paranormal Liberation War, the name of "One For All" was leaked to the public when people overheard Endeavor mentioning it during his fight with Tomura. Initially unaware of what it meant, people were able to piece together that it is related to All For One due to the similar name.

In the aftermath of the War, Toshinori was confronted by Best Jeanist and Hawks about One For All and how it was connected to Tomura chasing after Izuku during the battle, so Toshinori discloses everything to Endeavor, Hawks, and Best Jeanist. Izuku and Toshinori also proceed to reveal the truth to Izuku's mother, Inko, and Izuku himself writes personalized letters to each of his classmates in Class 1-A about the secret before leaving U.A..

At a press conference, Endeavor, along with Hawks and Best Jeanist, deny knowing anything about One For All, to protect Toshinori and Izuku, however the public continued to question the heroes, as more information started to leak out. While still unaware of its transferable origins, many civilians have been able to deduce that One For All is a special power that Izuku possesses, which is why he's being targeted by Tomura; this being confirmed to the civilians seeking sanctuary at U.A.. Most of the major Heroes now know the truth, as they use this knowledge in their planning for the Final War to defeat the Villains for good.

Due to the relationship between One For All and All For One, Izuku is given the primary role in directly dealing with Tomura and All For One's vestige, having trained and mastered the Quirk enough to unlock all the Quirks of the users and use their power to achieve an equivalent of 120% of One For All's power. It has become so powerful it helped disrupt All For One's forceful merger with Tomura, giving him the opportunity to strike back at his master and attain full use of the All For One Quirk itself. Proclaiming he has no need for One For All, Tomura's goals fully diverge from his master as he proceeds to face down Izuku to destroy him and his Quirk for good, aiming to remove the one person capable of halting his quest for global annihilation.

## Description

One For All is a transferable Quirk that can be passed on from one user to the next. Its name comes from its nature; being 'one' Quirk for 'all' people. In order for the Quirk to be transferred, the recipient must ingest a sample of the predecessor's DNA (ex: a strand of hair or a drop of blood).

The origin of One For All is itself a powerful will that refused to submit to All For One. For this reason, One For All cannot be stolen by any means. The Quirk cannot be transferred to another person unless the current wielder intends to pass it on, as demonstrated when Stain ingested some of Izuku's blood but did not inherit the Quirk. However, according to All Might, while One For All cannot be stolen, it can be forcibly transferred, as the recipient need not agree to inherit the Quirk in the first place. Since One For All can't be forcibly taken, it is one of the only Quirks that can be used in combat against All For One, as any user of All For One would simply be able to steal most other Quirks.

One For All also allows the user to stockpile an enormous amount of raw power, allowing them to significantly enhance all of their physical abilities to a superhuman level. This results in unbelievable levels of strength, speed, agility, and durability.

The user can focus the stockpiled power into a single body part, or spread the power evenly throughout their body, although, focusing the power puts a greater strain on the part of the body where the power is focused. The user is also able to control the percentage of the power that they activate. One For All can even grant the user an exceptional strength boost to their given Quirk if they have one.

The core of One For All has grown in strength from being passed from user to user, and the Quirk Factors of all of the previous users have merged into the core. The current user, Izuku Midoriya, has the exclusive ability to access the Quirks of the previous One For All users. The Quirks have significantly increased in strength since they were used by their original users; this is due to the nature of One For All's core stockpiling power and increasing in strength from user to user.

In addition to the Quirk Factors merging with the core, One For All carries echoes of the consciousnesses of all of the previous users. One For All has some kind of subconscious realm where the previous users can manifest. It is later revealed that this is due to the fact that Quirks are engraved with the consciousnesses of their users, so any new user who receives One For All has their consciousness embedded into the subconscious realm. It was originally believed that these "vestiges" can only be embedded into One For All if the user possesses a Quirk, however Toshinori proved this to be false: since he didn't have a Quirk or a Quirk Factor to have his consciousness copied into, Toshinori instead was able to actually imbue a true piece of his consciousness inside of One For All. This allows the fragment conscious to fully interact with the other users and share with them everything the real Toshinori knows, which is how the other vestiges were able to learn about the life shortening side-effect of One For All.

The subconscious realm within One For All was originally a barren landscape surrounded by darkness, and vestiges of the previous holders could only share brief visions with one another. However, after Tomura and All For One attempted to steal One For All, they drew the vestiges out by sheer force, stabilizing the vestiges within and allowing the current and previous users of One For All to communicate with each other freely. The realm took the form of the ruins of a conference room with chairs, one for each holder, though the second and third users initially choose not to sit and stand in the corner with their backs turned. The realm resembles the room where Yoichi was locked away by All For One, where the stockpiling Quirk was forced on him, and where he was eventually rescued by the Second and Third users; the birthplace of One For All itself. It also seems to have some connection to One For All's counterpart Quirk, All For One.

After having been stabilized, the previous users can now fully interact with Izuku whenever they wish, freely manifesting as spirits to give Izuku advice on their Quirks and how to best use them. It is also suggested that One For All has a phenomenal ability to allow users to sense other predecessors when they had the Quirk, as if they had a telepathic link to the deceased or former users within the subconscious realm, even long after their deaths, such as All Might sensing the other users, as well as himself, within Izuku despite giving up his Quirk. Izuku sensed the wary dangers of Tomura being usurped by All For One, and his crying self deep within the psyche and desired to save him in some way, and Nana and the other former users were able to telepathically sense these emotions because they are now synched with him inside of One For All. Furthermore, since One For All and All For One are counterparts to each other, the vestiges of the previous users resonate with the other Quirk and can peer into each other's inner workings, as shown when the previous users of One For All were able to see All For One within Tomura during their next encounter, and vice versa.

One For All draws power from the cries of help of those in need, as they are like a direct order to the user. It also seems to alter the user's appearance in different ways. For All Might, it significantly enlarges his muscles and overall body mass to make him look like a completely different person, similar to a giant. For Izuku, usage of One For All causes the empowered part of his body to glow, with vein-like lines crossing through each other. His body also generates crackling, green energy that resembles lightning bolts when he activates Full Cowl. It is unknown what the usage appearance of One For All looked like for its previous handlers, however.

One For All itself can be duplicated, but since it is an accumulation-type Quirk, the power stored inside cannot be duplicated as shown when Neito Monoma did not gain any substantial increase in power after copying it.

### Weaknesses

When One For All is transferred, the new user's body is not naturally suited to it as they normally would be with a Quirk they were born with (ex: someone who breathes fire doesn't burn their mouth while using their ability). In addition, One For All is a lot to handle; if one's body can't handle the power, then their body could be blown apart. Because of this, the successor must undergo intense and rigorous physical training.

Even after inheriting the Quirk, it takes time for the new user to adjust to One For All and learn how to properly control it. While Izuku trained his body into a suitable vessel for the Quirk, it was rushed to a period of ten months for him to be ready for U.A. High School's Entrance Exam. Using the Quirk while inexperienced can easily lead to self-injury, most notably with Izuku, who could only use it in short blasts of power which would break his limbs as a result. Only when Izuku learned to channel One For All's power evenly throughout his whole body was he able to stop this self-injurious habit and begin honing the Quirk's power as his own. Even so, repeatedly damaging his body led to extreme consequences, such as the ligaments in his arms becoming frailer, to the point where he now risks losing total function of them should he continue to use One For All recklessly.

After One For All is transferred, the previous user is left with only residual power from the Quirk (or "leftover embers"). While they would still be able to utilize the power to essentially the same degree as before, continuous usage of it will cause their power output to decrease, until the wielder is not able to make tangible use of the Quirk at all. After All Might's final battle against All For One, his ability to sustain his Muscular Form was reduced to seconds, rendering him unable to make any use of his residual power.

Like with all Quirks, the ability to use One For All is strongly tied to the user's physical health and well-being. As such, they will find it harder to handle the Quirk's raw power should they face negative health issues, even if they were strong and physically conditioned enough to inherit it. Examples here include Yoichi, who could not make proper use of One For All due to his weak body and sickly state, despite being the Quirk's original owner. Another example is with All Might who gained permanent, debilitating injuries following his first battle with All For One, limiting his ability to keep his empowered form active to only a few hours a day and thus hindering the use of his Quirk. As mentioned above, after passing One For All on to Izuku, this time frame continued to deplete rapidly.

Following the research conducted by All Might, as well as the discourse of the One For All vestiges, it is revealed that One For All can affect the user's lifespan. If a person who already has a Quirk receives One For All, the extra Quirk places an enormous burden on their body, depleting the user's life force and shortening their lifespan. It is analogous to adding water to an already-full cup, causing it to overflow and breakdown. The rate at which the person's life decays is unknown, but Hikage, the fourth user, received One For All at the age of twenty-two and died of "old age" eighteen years later, at the age of forty. This weakness can be circumvented if an inheritor does not already have a Quirk, since the Quirkless user would be an "empty cup" that is filled by One For All. However, this weakness has become more of a concern due to the number of people born Quirkless becoming fewer and fewer, as well as One For All continuing to rise in power, thus limiting potential successors who can handle the Quirk safely.

While One For All cannot be stolen by any means, the users do admit that, theoretically, it is possible for All For One to steal One For All, provided he is able to overwhelm the collective will of all its users. Yoichi speculates that as the reason why All For One raised Tomura to have such overwhelming rage and hatred, as it would be able to eat away at the willpower of all the users and therefore bypass One For All's immunity to be stolen.

When manifesting themselves in the unconscious realm of One For All, the current user's body is not all there at first. Some parts, such as their mouth, take time to learn how to fully manifest, making it more difficult to communicate with the other vestiges. This weakness was inadvertently removed by All For One when he unsuccessfully attempted to steal One For All from Izuku. Consequently, there are now no communication impediments between the One For All users, allowing the past users to freely converse with Izuku whenever.

### Assimilated Quirks

The Quirk Factors of each of the previous users have merged with the core of One For All and have since increased in strength due to One For All's nature of stockpiling power. Izuku is the first user capable of accessing the Quirks of the previous users. Because All For One would constantly hunt and steal the most powerful Quirks, most of the user's Quirks are rather unexceptional by themselves and do not have enough potential to be raised to "Ultimate Move" level. However, despite this, the Second User has stated that the stockpiled energy of One For All has resulted in his Meta Ability evolving beyond anything it once was, and could be devastating if not used carefully.

The Quirks within One For All are:

* **Gearshift**: The Quirk wielded by the second user. This Quirk allows the user to alter the speed of anything they touch, allowing them to accelerate the force of a target, either by enhancing the impact force of their own strikes or by causing the target to lose control of their own velocity.
* **Fa Jin**: The Quirk wielded by the third user. This Quirk allows the user to build up and store kinetic energy by performing repetitive movement, this energy can then be released as an explosive burst of speed and power.
* **Danger Sense**: The Quirk wielded by the fourth user, Hikage Shinomori. This Quirk allows the user to detect nearby threats.
* **Blackwhip**: The Quirk wielded by the fifth user, Daigoro Banjo. This Quirk allows the user to produce tendrils of dark energy which are useful for long-range grappling and increasing the user's mobility.
* **Smokescreen**: The Quirk wielded by the sixth user, En. This Quirk allows the user to generate thick clouds of purple smoke from their body, which can obscure people's vision.
* **Float**: The Quirk wielded by the seventh user, Nana Shimura. This Quirk allows the user to levitate.