Was Once A Man / Anime & Manga

• In Ahiru No Oujisama, Mister was once a prince, but is now an ugly dog. He turns back...after being a short ugly weirdo for a bit he gets back to being a bishonen.
• Assassination Classroom: Koro-sensei was once a notorious human assassin, before he was captured and gradually transformed into a tentacled monster via Playing with Syringes.
• In Attack on Titan, the Titans are all human. More specifically, they are all members of the Eldian people descended from the original Titan, Ymir Fritz. When exposed to a special serum made from spinal fluid, they are transformed into a mindless Titan and trapped in this state until killed or lucky enough to consume one of the Nine Titans. The Nine Titans (such as Eren) are the only Titans capable of regaining their human form and controlling their powers, while all others remain in a state once described as an "endless nightmare". Little surprise the oppressive Marleyan regime uses it as a form of execution for Eldians.
• Berserk: Every Apostle was once human. Humans become Apostles when a creepy little egg-like item called a Behelit comes into their possession and they hit an emotional nadir where they will do anything to get out of their current situation. At this point, the Behelit rearranges the features scattered upon its surface into a human face and screams, which summons the four (later five) dark gods of the God Hand, who proceed to offer him or her the chance to become a Apostle in exchange for the sacrifice of those closest to them. It also turns out that every member of the God Hand was also human, and they were created with the use of Behelits as well. While Apostles do sometimes retain the personalities they had when they were human, all too often they commit Transhuman Treachery, with many of them preferring to dine on their former species. When Apostles die, they typically revert to their former human forms after their spirits are Dragged Off to Hell.
• Bleach. Every Hollow started out as a lost human soul. Eventually, it lost its heart, whether through time or the attacks of another Hollow, and became a monster, feeling nothing but the desire to murder and a hunger for souls. If they survive long enough, Hollows can "get over it" on their own (or if someone else removes their mask or uses the Hogyoku on them) and become Arrancar, who are intelligent creatures and apparently don't need to eat souls anymore (considering that they have copious amounts of regular food in Las Noches and only three or so Arrancar are ever shown any desire to eat anyone... and of those, one is a Mad Scientist who's turned his minions into edible medicine and another has the ability to gain the powers of anyone he eats, so they're not just eating for the sake of eating.)
• BNA: Brand New Animal: Michiru and Nazuna were once human schoolgirls, until they both got into a car accident, and a blood transfusion mixup changed their lives, as they both got beastman blood and end up transforming into a tanuki and a kitsune, respectively.
• Chrono Crusade has an unusual example revealed towards the end: Pandaemonium was once a human woman pregnant with twins. The demons kidnapped her and transformed her into the monstrous, Mind Rape-using queen she is — and transformed her human children, Chrono and Aion, into demons as well.
• Claymore: Each and every Awakened Being and, perhaps more shockingly, the Abyss Eaters. Even more shockingly, the Youma.
• Daltanious: According to Earl, Beralios was once an ordinary lion "from Africa" until the Heliosian Emperor ordered him to be kidnapped, taken to their planet and experimented on. As a result, Beralios is now an Animal Mecha.
• Delicious in Dungeon: The zombies, walking skeletons and ghouls are the re-animated corpses and ghosts of adventurers who couldn't be revived for various reasons.
• The Demon Prince of Momochi House: Aoi happened to wander into the titular house as a child, only for the house to choose him as "Omamori-sama." Meaning, he becomes a Nue. Luckily, he can shapeshift between his human and Nue forms.
• D.Gray-Man: Akumas. Their hunters know, at least in abstract, that they contain the souls of innocent people forever tortured until the Akuma are destroyed and they're released, but only Allen has to confront the vision of them on a daily basis. As with Hollows (though in Bleach it's a different story), leveling up obscures more and more the original souls, until even Allen can't see them anymore. It also makes new souls in the process.
• Elfen Lied: Anna, when first introduced, is an adorable and happy, if dimwitted, young girl who loves to run. Her father is disappointed with her lack of intelligence, and transforms her into an enormous, horribly mutated creature with super-intelligence and precognitive ability. She cannot support the weight of her gigantic head, and so must remain virtually immobile in a pool. Remember how she loved to run? Yeah. She gets better and is overjoyed when she realizes she can't do simple math.
• Fairy Tail: The dragon Acnologia and Spriggan 12 member Irene Belserion were originally human Dragon Slayers. However, their magic eventually ran out of control and morphed their bodies into that of dragons though Acnologia figured out how to retake his human form at will while Irene regained her physical human appearance thanks to Zeref, though biologically she's still a dragon. Turns out this is something that happens to all Dragon Slayers eventually, unless they have certain antibodies to prevent it. The present-day Dragon Slayers' Dragon parents sealed themselves in their children for seven years to create those antibodies.
• Franken Fran: This happens a lot to people who go under Fran Madaraki's scalpel, or that of her creator.
• Fullmetal Alchemist:
  • Shou Tucker, the Sewing Life alchemist, fuses his daughter Nina with her dog, Alexander. He also fused his wife with another beast a few years back, in order to gain his certification. Both chimeras are able to talk, and they both make it known they're not happy with their new existence. The one made from his wife asks to be killed and when, it isn't obliged, starves itself. The one made from Nina and Alexander is killed by Scar.
  • This happens to Tucker himself, too, but only in the 2003 anime adaptation — in all other versions he's executed for his crimes. He's made into a chimera and officially listed as having been executed by the state so that he can continue his experiments for the government in secret.
  • There are a number of other cases in the series. Perhaps most notable are the chimeras working for Greed and Kimblee, who were soldiers fused with animals — though most of them retained their human forms, they're none too happy about their situation and the latter join the heroes so that they can eventually become fully human again—and the former serial killers used as guards at Laboratory 5, who were officially executed but actually had their souls bonded to suits of armor just like Alphonse. Slicer and his brother lament their situation and, in the 2003 version, the latter actually ends up committing suicide, but the other guard, Barry, is perfectly fine with it and if anything prefers his new body to the old one.
• Hellsing: In OVA 8, it is revealed that Alucard was once Vlad the Impaler.
• Inuyasha: Naraku was once an ordinary bandit. He has made a pact with a lot of lower youkai, and thus he has become who he is.
• JoJo's Bizarre Adventure: Diamond is Unbreakable Has the Nijimura brothers' father, who was once a normal human being, but after the death of his wife he grew into a depressed state and began abusing his sons. At one point, he met up with DIO and became his subordinate. However, because DIO didn't trusted him, he implated a flesh bud on the father which activated upon his death, transforming the father into a mindless creature who can only remember his family.
• King of Thorn has the "mother monster", which is eventually revealed to have been a human (Shizuku) who succumbed to The Virus.
• Made in Abyss has creatures that are known to show up occasionally in the depths, called Narehate, that are known to be the living remains of those who traveled to the Capital of the Unreturned and...well, returned. The ones encountered in the Sea of Corpses and layers above generally look completely inhuman and have no shred of sanity or capability for rational thought left. The only apparent exception is the rabbit girl Nanache. Later, more human-like Narehate are discovered in the Capital of the Unreturned, although they appear to have become Narehate through a different mechanism.
• In Magi: Labyrinth of Magic, all the Djinns were revealed to be once members of the sentient species that were freed and later allied with Solomon.
• Miss Kobayashi's Dragon Maid: It's implied that Fafnir was not born as a dragon but instead transformed into one, much like his mythological counterpart.
• The nomu in My Hero Academia are artificially created beings made from dead humans and given one or more quirks by All for One. Some are more animal-like and can’t really think for themselves, but the high-end nomu do have some independent thought. Many of the bodies are former small time criminals but there are exceptions, like Aizawa and Hizashi’s close friend who was turned into Kurogiri.
• Naruto:
  • The thousands of Zetsu clones were victims of the first Infinite Tsukiyomi rather than clones of Hashirama. The end goal of Kaguya is to create an army using the same technique.
  • The Juubi was created when Kaguya merged herself into the God-Tree.
• One Piece has the island of Dressrosa. Their humans and living toys live together. Except unlike other fantastic beings in One Piece, these "toys" were once humans but turned into toy creatures by a Devil Fruit user.
• Many (though not all) of the various monsters from One-Punch Man were formerly human. Humans can naturally transform into monsters if they overly indulge in obsessive behaviors (i.e. Crablante, a guy who ate too much crab meat until he eventually turned into a grotesque crab-human hybrid); or by some external methods (like drinking a mutagenic serum, or eating "monster cells" to instantly trigger a metamorphosis). This gets heavily deconstructed in Supreme Hero arc, where Amai Mask reveals to be a monster all along, (though ironically this is meant to be a Good All Along, as previously in the series he made very morally questionable choices, albeit in the name of "justice"), while still reteaning his humanity and trying to make Saitama a real hero, by wanting to finish him off when the world watches. Fortunately, Saitama doesn't want to kill him, and helps Amai hide from the public for some time. Later, it's revealed Amai Mask is able to shapeshift into other forms, which is how he avoided from being caught by Hero Assocation and media.
• In Puella Magi Madoka Magica, it turns out that every single Witch that the magical girls fight (those that aren't ex-familiars, anyway) was once a magical girl herself, and to make things even worse, every magical girl is ultimately doomed to become one of the very monsters she's been fighting, unless she dies first.
• Rosario + Vampire: Hokuto Kaneshiro is revealed to be this, having been human like Tsukune before being injected with Kiria's blood. His new true form is infinitely more horrifying.
  • Over the course of the series, Tsukune also undergoes a series of translations that make him less human and more monster, but under more controlled circumstances. He learns to control each of them and thus even after becoming fully vampire his mind is unchanged from when he was human. And when not actively using his powers he still looks human, other than being better looking than he used to be.
• Sailor Moon: Many of the monsters were originally human. Some of the Youma in the first season and the Phage of the last season. Sailor Moon's power to restore the Phage to normal actually shocks the Starlights, as they had to simply destroy them because they lacked the power to do so without their princess. A single human-based Daimon also appeared in a flashback which was closer to their manga version. The lemures were also either human or human-like aliens before their queen stole their dreams. Then they got weird. And the Witches Five were, essentially, humans possessed by Daimon Seeds. Also inverted, where a few enemies like the Great Youma were monsters born into human form.
• Seraph of the End: Vampires were once humans themselves.
• World Embryo: The enemy virus, Kanshu, were once humans who lost their memories and transformed into hideous beings upon listening to the infected radio signals in their cell phones.
• In Xam'd: Lost Memories, it becomes clear fairly early on that both human form weapons and Hiruko are former humans.
• Yu-Gi-Oh!:
  • During the Virtual World arc, Kaiba's former board members, the Big Five, had uploaded their minds into a virtual reality game to defeat him; their own defeat led to their minds being trapped in cyberspace. Later, Noah discovered them and brought them to his separate virtual world, where they assumed the forms of various creatures from the Duel Monsters game in order to challenge Kaiba and his allies. They later managed to assume a human form again by taking over the virtual avatar of Tristan Taylor; Tristan himself became trapped in the form of a robotic monkey after losing a duel with one of the Big Five but was restored to normal upon exiting the world and returning to his physical body. Kaiba's stepfather Gozaburo also demonstrated the ability to assume a monstrous form in the virtual world.
  • Yubel, the Big Bad of season three of Yu-Gi-Oh! GX. They willingly gave up their humanity and was turned into a demon in order to become a spiritual guardian for their ward (who would become Judai in later life).
  • All of the villains originating from the Bad Future of Yu-Gi-Oh! 5Ds, including Z-one, Aporia, and Paradox. The first is a cyborg with god-like powers, while the other two are android incarnations of their previous selves.
  • The Seven Barian Emperors, the antagonists of the second season of Yu-Gi-Oh! ZEXAL, were all once human, and they can assume human forms that resemble - for the most part - their original forms.

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