Fanfic / Personality Swap AU

Personality Swap AU is a series of My Hero Academia fanfics by BelleAmant. They can be read on Archive of Our Own here.

The series starts with Aizawa giving his students a lesson in personas by making them imitate each other for a day. Most fail, but Izuku pulls off his role perfectly, even mimicking his target's fighting style. As a result, Aizawa decides to start assigning Izuku other people to imitate.

The series divides itself into two "seasons." The first was completed as of 24 October 2021, and consists of 33 short stories and one notes section. The second debuted on 23 May 2022 and currently contains 16 complete short stories.

An ongoing Audio Adaptation of the series is being created by RuneLore. The recordings are available here. Currently 17 of the short stories have been adapted for this format.

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This AU contains examples of the following tropes:

• Accidental Truth: The cover story for One For All is that Izuku was just a really late bloomer when it came to manifesting a Quirk. It turns out that this is 100% correct and, because of One For All, nobody—not even Izuku—recognizes the signs of Izuku's naturally occurring Quirk until it becomes undeniable.
• The Ace: Izuku, by the time he's in his third year. He's easily the most powerful class member after gaining mastery of Mimic, incredibly versatile and talented, and excellent at balancing his schoolwork, extra assignments, and internships. He always makes time for his friends, and he's even a good instructor to his fellow classmates, with underclassmen coming to him for advice. He's effectively UA's golden boy, so it's no surprise he becomes the leader of their year's Big Three.
• Achievement In Ignorance: When Aizawa and Izuku run into Eri and Overhaul on the first evening patrol of Izuku's internship, Izuku takes Overhaul down easily because Aizawa has erased everyone's Quirks and Izuku's better than Overhaul at fighting Quirkless. Izuku didn't realize the kidnapper was Overhaul, an S-rank villain, until Sir Nighteye's meeting, and never knew nor needed to know the nature of his apparently powerful Quirk.
• Actually Pretty Funny:
  • Mirko is noticeably amused by Izuku dressing and acting just like her.
  • Mirio's reaction to Izuku effortlessly copying Toga on the fly? A gleeful "Midoriya was terrifying. Neat!"
• Ambiguously Related: In the one-shot explaining the specifics of Mimic Quirk, the author notes that Izuku, Monoma, and Toga are likely related to each other, based on the similarities between their respective quirks. All of them are also in some way descended from All for One.
  • The interlude "A Parent's Beliefs" reveals Izuku is in fact All For One's son.
• Armor-Piercing Response:
  • Izuku-as-Bakugou insisting he's "not All Might's boy" visibly hurts the pro hero's feelings. It's only when All Might learns Izuku is method acting that he gets over it.
  • When called to testify in the case against Aldera, Izuku ultimately shuts down their lawyer's attempts at victim-blaming this way:
    Izuku: I'm just a kid, sir. And that's all I was then, too. I didn't want to seek attention, I didn't want to cause trouble, I didn't goad anyone on or ask for them to hate me. I was just a kid, sir, with a Quirk that hadn't presented yet. If you can tell me how I should be blamed for that, or for the people who saw me and thought I was a good punching bag for their frustrations, please let me know. I've been trying to figure it out for over a decade, now.
• Astonishingly Appropriate Interruption: In "Present Micdoriya", Aizawa interrupts Midoriya and Present Mic rapping "Guns and Ships" from Hamilton:
  Midoriya: LAFAYETTE!
  Present Mic: Watch me engaging 'em, escaping 'em, enraging them, I'm-
  Aizawa: Hizashi!
• Aw, Look! They Really Do Love Each Other: Bakugou admits during their third year's Sports Festival that he sees Izuku as his best friend.
• Be Careful What You Wish For: In the Interlude, "A Parent's Beliefs," All For One spies on Izuku and sees him crying. He wishes Izuku's tears were for him—at his father's defeat and capture. It turns out they are—Izuku has just finished writing his final email to Hisashi, announcing that Izuku's done mourning a father who's never contacted him in eight years, that he's better off without said father, and that he has people who love him and are willing to be the father Hisashi isn't.
• Contrived Coincidence: Izuku and Aizawa happen to run into Overhaul while on patrol and capture him. Several days later, they're called in to participate in a raid on Overhaul's organization. When Sir Nighteye mentions that nobody has seen Overhaul for some time and the heroes aren't sure what he's up to, the pair are astonished and tiredly amused respectively.
• Curb-Stomp Battle: Izuku and Aizawa Vs Kai Chisaki. Aizawa used Erasure, and Izuku proceeded to deliver a Quirkless beatdown.
• Daddy Had a Good Reason for Abandoning You: Played with. Izuku believes his father chose to abandon him and his mother. In reality, Inko remembers Hisashi being incredibly supportive and loving towards both of them but hasn't been able to bring herself to tell her son his father is dead, and has been for years. Then it turns out Hisashi actually isn't dead but couldn't return home due to All Might giving him a cover-blowing injuries.
• Despair Event Horizon:
  • Invoked and averted regarding Sir Nighteye's plans for Izuku. Sir Nighteye's section in "Changing Fate (With or Without You)" narrates his intention to weaponize his position as Izuku's mentor to bully Izuku to a "breaking point" where Izuku would surrender One For All to Mirio. The plan is upset by Izuku rejecting the internship, giving Sir Nighteye his own The Reason You Suck speech on the way out.
  • Played for laughs with Aizawa's reaction to Izuku impersonating Ms. Joke.
• Didn't See That Coming:
  • The AU begins with Aizawa assigning the 1-A students to impersonate someone else in the class of his choosing for the next school day, with Izuku assigned to impersonate Bakugou. After Izuku earns a perfect grade on the assignment, Aizawa decides to have him impersonate the rest of the staff at UA (thus bringing chaos and mayhem to the school). Aizawa and Nezu both then decide to nurture his acting and analytical talents, bringing significant changes from canon. At first these changes are predictable to them, like Izuku's improved confidence or the downfall of Aldera Junior High. Then Izuku mimics another student's quirk in the middle of class.
  • Sir Nighteye deliberately plans his first meeting with Izuku to break the boy just enough that he'll give One For All to Mirio. However, the man's information on Izuku was months old, as he'd not kept tabs on the boy's development after the Sports Festival. Not only does Izuku pass Sir Nighteye's test, he's so angered by the man's attitude that Izuku refuses to intern with him and simply leaves:
    Izuku: I’ve changed my mind. I think I’ll find someone else to teach me.
    Sir Nighteye: You passed. You...bested me. You won fair and square.
    Izuku: I did. And now I am deciding, fair and square, that I do not want to be taught by a man who thinks he has the right to say whether or not my Quirk is my own. I came here hoping to find a teacher, someone to build me up. If I wanted to hear someone belittle me, I’d go back to my middle school educators, Sir.
  • Eri accidentally uses her Quirk on Izuku-as-Kurogiri, causing him to instantly collapse. When the boy wakes up, he's now Izuku-as-Shirakumo.
• Entertainingly Wrong: A video of Izuku seemingly working with Mirko causes Sir Nighteye to assume the boy is interning with her when he's actually interning with Aizawa.
• Even Evil Has Loved Ones: For all his villainy, Hisashi Midoriya—All For One—appears to genuinely love his wife and son, and is remembered by Inko to have been an incredibly supportive husband and father.
• Even the Guys Want Him: Izuku-as-Midnight is stated to be so attractive that his entire class finds themselves questioning their sexuality. When Izuku spends a day acting as Recovery Girl, he has dozens of students coming to him for a healing kiss.
• Epic Fail:
  • In the first story, the entire class was supposed to imitate one of their classmates. Some of them were outright terrible at it, such as Koda acting like himself but throwing glitter around (to imitate Aoyama) or Iida's complete inability to speak in memes.
  • After seeing how many students were attracted to Izuku-as-Midnight, Aizawa tries to give him the least sexy assignment possible: Recovery Girl. Aizawa realizes too late that what makes Recovery Girl unattractive to most (her advanced age) doesn't actually apply to Izuku, meaning what actually results from Izuku's impersonation is an Attractive Bent-Gender Hospital Hottie. Further, Recovery Girl's Quirk involves kissing. According to Recovery Girl, dozens of students from all grades came to her office with exaggerated claims of injuries that day, likely hoping to be "treated" by Izuku—meaning that, far from discouraging the attraction displayed by his class towards Izuku, Aizawa's assignment got Izuku noticed by the entire school.
• Fatal Flaw: In both class-wide impersonation exercises, Bakugou demonstrates his own considerable skill and dedication towards impersonation. The thing that causes him to fail, however, is his inability to handle how others portray him: as a violent, wrathful, cruel, self-obsessed bully. In fact, he's the only student who actually does worse during the second assignment than he did in the first, specifically because of his furious outbursts.
• Hoist by His Own Petard: Aizawa chooses Izuku's impersonation assignments mostly by what will unsettle and upset his coworkers the most. Much to the amusement of his targets, several assignments end up upsetting Aizawa himself more than his coworkers, with special mention going to the Recovery Girl impersonation. When Aizawa's actions inspire Nezu to give Izuku impersonation prompts like Mirko and Ms. Joke, all the rest of the staff can do is laugh at Aizawa's misery.
• Innocently Insensitive: In "A Jump Ahead," when informed that they'll be having a third class swap assignment, Kaminari asks if Izuku will be impersonating Shirakumo since he's the newest student. Given how that went previously, Aizawa doesn't react well.
• Internal Reveal: Izuku finds out his father is allegedly dead in "Don't Say It Wasn't True."
• Locked Out of the Loop: The number of loops in the Midoriya family is staggering.
  • Izuku is not aware of his father's supposed death. Inko finally tells him in Don't Say It Wasn't True.
  • In turn, Inko is unaware of the truth behind her son's "late quirk" and then his actual quirk coming in recently.
  • Hisashi doesn't know why Izuku keeps writing emails to him since he doesn't know Inko didn't inform their son of his alleged death.
  • Neither Inko nor Izuku know that Hisashi is All for One.
• Loved by All: By the time he enters 3-A, Izuku is already famous and widely admired by the public as the Acting Hero, and both his own class and the rest of the school look up to him. He's every teacher's favorite student, including Nedzu's, but no one holds it against him because they all admire him just that much. It surprises no one except Izuku himself that he's named the leader of the next Big Three.
• More Insulting than Intended: Inverted. Izuku compares Sir Nighteye to Izuku's own middle school educators. While Sir Nighteye has looked over Izuku's official documents, he shows no indication of knowing that Aldera Middle's treatment towards Izuku was quite literally criminal.
• Maybe Magic, Maybe Mundane: Izuku is able to perfectly mimic anyone he's told to from speech patterns to instinctive reactions to fighting styles, to the extent that it verges on Beyond the Impossible, with him seeming to know personal information his prompts have never publicly shared and even appearing to use their Quirks. While mundane solutions such as research, Awesome by Analysis, and creative use of One For All are all evident, assumed, and discussed by his audience, they don't definitively explain every instance of this, particularly as the series goes on and Izuku's impersonations practically verge on possessions. Whether Izuku is just that amazing an actor who is Awesomeness by Analysis or whether there's something more fantastic involved remains unclear. Until the 24th story when Izuku mimics Monoma and somehow copies Bakugo's Explosion Quirk.
• Method Acting:
  • The AU starts with Aizawa assigning the entirety of Class 1A to act as one of their classmates for the day. Bakugou, playing Izuku, ends up breaking character during his fight with Izuku (playing Bakugou) in Foundational Hero Training, whilst Izuku flawlessly impersonates Bakugou's personality and fighting style, even mimicking his explosive 'flight' using One for All
  • Aizawa, impressed by Izuku's perfect portrayal of Katsuki, sends him several other such assignments. Every time, Izuku stays completely in character the entire day, including using their fighting styles and finding a way to imitate their Quirks. Given that Izuku will share information that only his characters should know and seamlessly switch places/work with them^note Toshinori finds Izuku-as-Snipe sharing a story that only Toshinori himself and Snipe know and Mei and Izuku-as-Mei perfectly work together on various gadgets, even passing each other needed tools without speaking a word, several note that it's almost as though he's been possessed by his role.
• Mundane Solution: After Izuku awakens a mimicry Quirk, Aizawa gives him an assignment that would make it very obvious if it happens again.
• Never My Fault: All For One blames All Might for separating him from his beloved wife and child. Despite noting himself the Laser-Guided Karma involved considering what All For One had done to All Might and Shimura Nana, it doesn’t occur to him that he could have just quit villainy while he was ahead and retired to live the peaceful family life he apparently adored, and that he is the one who gave all that up to fight All Might.
• Oblivious Guilt Slinging: After Sir Nighteye deliberately treats Izuku like an inferior and waste in the hopes that this would break him enough to give his Quirk to Mirio, Mirio comes in and spends the entire next conversation talking about how awesome Izuku is and how Mirio himself doesn't think he'd be able to handle what Izuku's had to deal with. Mirio also casually assumes Nighteye used a good faith intimidation approach, not realizing Nighteye fully intended to hurt Izuku. All of this just rubs Nighteye's realization of his mistake in his face.
• Oblivious to Love: After two dozen stories, Izuku still has no idea that Todoroki has the hots for him. It takes briefly impersonating Todoroki himself for Izuku to realize Todoroki's feelings.
• Other Me Annoys Me: The only person who really has a problem with Izuku's impersonation of themself is Bakugou, who can't handle his own cruelty mirrored back at him. The insults Izuku parroted back during the initial exercise are the Rage Breaking Point for Bakugou's own attempt at impersonation (Izuku), and the memory of that treatment directed towards him haunts Bakugou from there after in his private moments. Later, when Shinsou impersonates Bakugou, Shinsou's blunt portrayal of Bakugou's violent ego makes Bakugou angry enough to break character again (this time, out of playing Aoyama).
• Parental Substitute: All Might and Aizawa are this for Izuku, to the point where Izuku basically refers to them as his two dads when writing to his biological father. Played for Drama in an otherwise fairly silly series, as this fuels All For One's wrath, since he genuinely seems to love his son and sees it as All Might's fault he couldn't be there for Izuku.
• Parental Title Characterization: Reflecting his acceptance of their roles in his life, Izuku notably switches to referring to both Aizawa and Toshinori as his Dads in the second season.
• Passed-Over Inheritance: All For One's motive for hunting down the previous holders of One For All turns out to at least in part be because he sees the Quirk as a part of his brother that was wrongfully passed out of the family. He's actually pleased it's been given to Izuku as he sees this as the Quirk being returned.
• Pet the Dog: Occasionally, Aizawa will assign Izuku a role that he knows one of his coworkers will enjoy, just to be nice for once.
• Point of Divergence: Because Izuku has gained range and confidence in his abilities through his impersonations and the support network that they have opened for him, Izuku stands up for himself to Sir Nighteye and rejects his internship, instead choosing to intern with Aizawa. Because of this, Aizawa's schedule for those days also changes. This puts them in the right time and place to run straight into Overhaul on Izuku's first evening patrol; the two take him down easily since Overhaul isn't experienced in fighting quirkless.
• Powers Do the Fighting: This comes back to bite Overhaul in the ass. Unlike Izuku, he has no experience fighting without his Quirk. So when both are caught in Aizawa's Erasure, Izuku easily manhandles the yakuza.
• Powers via Possession: Played with in all of the impersonations during which Izuku uses his prompt's Quirk and ultimately inverted with his inborn Quirk's main drawback.
  • Played with regarding Izuku's natural Quirk, which works by creating a mental link between him and whomever he's impersonating, enabling him to instinctively borrow information about them from their minds. Once this Mimic Quirk mixes with All For One, it enables Izuku to mimic his prompt's bodily abilities, such as their Quirk.
  • Inverted with his Quirk's main drawback: if Izuku impersonates someone for too long, or if his prompt's mental faculties are impaired, he can begin to lose his grip on his own identity under the act. When Aizawa assigns Izuku to impersonate Kurogiri, Izuku functionally becomes possessed due to Kurogiri's limited mental independence putting a limit on Izuku's own. This culminates with Izuku completely forgetting he isn't Shirakumo and even beginning to physically transform into him. While using the powers doesn't necessitate this loss of identity, Izuku's issue is that he runs the risk of effectively getting possessed via the powers he duplicates.
• "The Reason You Suck" Speech:
  • Sir Nighteye gives one to Izuku, blatantly calling him unworthy of All Might's Quirk, refusing to acknowledge it as Izuku's, and stating that Izuku uses the power like a fool.
  • Izuku immediately follows the above with one of his own for Sir Nighteye. He manages to very politely compare Sir Nighteye's demeaning and belittling behavior to his middle school teachers, implies Sir Nighteye isn't worthy of being called a teacher, rejects the "opportunity" to learn from him, leaves, and never looks back.
• The Reveal:
  • Izuku really is a late bloomer and his natural Quirk enables him to mimic the mental state of anyone he knows, including their memories, skills, personal tics, and general disposition. One For All empowered the Quirk further to the extent that Izuku can now access and use an individual's Quirk when mimicking them. Because of One For All, nobody realized Izuku's behavior was the manifestation of an unknown second Quirk until Izuku used Bakugou's explosions.
  • Inko's interlude reveals that Hisashi Midoriya died five years before canon (officially, at least). She decided not to tell Izuku because she considered him too young, and then just kept on not telling him.
  • All for One's interlude reveals that he is Hisashi Midoriya.
• Running Gag: When someone mentions or thinks about Nezu's lessons with Izuku, mysterious voices in other parts of the school begin chanting "Rat God Wednesday."
• Screw This, I'm Outta Here:
  • Played for Laughs with Iida's duel with Gran Torino!Izuku, which lasts for only a minute before Iida runs sprinting from the designated area chanting "Nope nope nope nope nope nope—"
  • Played for Drama with Izuku's response to Sir Nighteye's unfair test and belligerent attitude; he completes the test just to spite the hero and then leaves, stating he refuses to intern under someone like him.
• Shallow Parody: In-Universe. A lot of the class's impersonations of each other are this, especially during the first assignment. Some of them base their entire act around one exaggerated trait. It's implied that while Bakugou is generally good at acting, one of his problems in the first assignment that not even Aizawa noticed was that he only thought of Izuku as a sniveling crybaby. All of them get better as Izuku's own impersonations highlight everyone's multiplicities of character, including his own.
• Spotting the Thread: A stray comment from Izuku-as-Bakugou about how he had beaten Bakugou-as-Izuku's foul mouth out of him years ago leads Aizawa to have a talk with Izuku, ultimately leading to him finding out how he was mistreated at Aldera.
• Tempting Fate: During the first swap, Hagakure requests to play Momo or Izuku, prompting Bakugou to exclaim incredulously, "Why the fuck would you want to be Deku?!" Guess who gets assigned to impersonate Izuku.
• Took a Level in Badass: Izuku's acting improves his fighting ability to the point that he fights Mirio to a standstill by himself.
• Troll: Aizawa. A number of Aizawa's choices for Izuku's assignments are based on what would upset his coworkers the most, chosen "not out of malice or ill will, just out of the need for amusement." Many passages are devoted to expressing Aizawa's desire to instill panic and fear in his coworkers solely for the pleasure of their reactions.
• Vitriolic Best Buds: Katsuki becomes this to Izuku eventually, as they develop out of their victim-and-bully dynamic and into an actual healthy rivalry. The two regularly get into very destructive spars, but Katsuki privately admits to seeing Izuku as his best friend.
• Wham Episode:
  • Story 24, Mimic, sees Izuku use Monoma's Quirk to copy Bakugou's.
  • Story 35 reveals that Hisashi Midoriya was legally declared dead when Izuku was ten — because he's actually All for One and couldn't return injured after the fight with All Might — and Inko decide not to inform her son about it.
• Who Would Be Stupid Enough?: In "Mirukodoriya," All Might internally comments on his pride in Izuku, saying that "He couldn’t have found a more worthy successor of One for All, a better boy to call his son. Only a fool would believe otherwise." The scene Answer Cuts to Izuku's visit to Nighteye.

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