How does the world define monstrosity? Is it a question of nature, or of choices? Certainly, many monstrous characters have often been vilified, but others have made for amazing protagonists. These days, most shonen heroes bear a monstrous curse or wield some unholy power or another.
Given the undeniable success of shows like Demon Slayer, Jujutsu Kaisen, and To Your Eternity, monstrous main characters are certainly making a statement. But this is nothing new. Half-human, half-monster hybrid characters are an anime staple.
Note: Characters on this list have been selected on the basis that genetically, their bodies contain "monster" DNA, be it due to parentage or experimentation. For this reason, characters like Yuji Itadori and Naruto Uzumaki don't quite fit the bill.
10 Claymores Are All Half-Youma
Claymores didn't have much say in their fate or their future, given the circumstances that made them what they are. In a medieval fantasy world in which demons called youma devour villagers and lay waste to human beings, Claymores are forced to fight and destroy the monsters.
The thing is, Claymores are half-monster themselves. The product of experimentation that spliced youma DNA into young orphan girls, a Claymore's existence is unfailingly a bleak one. She's bound to spend her life maligned by society, hunting the very monsters she might one day become.
9 Rin Okumura Is The Son of Satan (Blue Exorcist)
Few teens get along with their parents 100% of the time, and that's the case for Rin Okumura, too. Though he and his twin brother were raised by a kind priest, his real father wouldn't be fun to deal with at Thanksgiving. Rin's father is none other than Satan himself, though his mother was human.
As the son of Satan, Rin wants nothing more in Blue Exorcist than to denounce his inheritance and kill his father. A classic anti-antichrist, Rin's got even more reasons than most folks do to want the devil dead.
8 Akihito Is Half-Youma (Beyond The Boundary)
Beyond the Boundary isn't as popular as many other Kyoto Animation productions, and it's a real shame. The show has a stilted start but gradually becomes a fantastic series about acceptance and growth. None of its characters are as simple as they seem to be, high schoolers who work as Spirit Warriors too.
Akihito Kanbara, the male lead, is actually half-youma, the product of a human woman and a monstrous father. Akihito hides his true identity, knowing his youma half is reason enough for him to be killed, given its destructive and ruthless spiritual power. Much of the series is about Akihito and the others coming to terms with their darker halves and accepting each other in the process.
7 Zero Two Is Part Klaxosaur (Darling in the FRANXX)
The worldbuilding in Darling in the Franxx often feels a bit overcomplicated, but the essential pieces are clear enough. Zero Two is powerful but not entirely human, and life has sometimes been hard on her.
Zero Two is a human-klaxo sapien, the only hybrid of her kind to survive the experimental science that created her. In the Darling in the Franxx universe, klaxosaurs are armored, dinosaur-reminiscent biological weapons intent on fighting humanity. Given this, mistrusting Zero Two is a no-brainer for many characters, and she longs to become entirely human.
6 Eureka and Renton Have a Son (Eureka Seven: AO)
Midway through mecha classic Eureka Seven, Renton and the rest of the cast realize that Eureka really isn't what she appears to be. In a society that's constantly fighting back scub coral - organic, environmental monsters unlike anything on earth - the revelation that Eureka is a Coralian, a being created by the scub coral, is a real doozy.
Even so, Eureka and the scub coral exist primarily to communicate with mankind, and as Renton and Eureka fall in love, the world grows closer to peace. Later, they give birth to a son, the protagonist of the lesser sequel series, Eureka Seven: AO.
5 Inuyasha's Yokai Heritage Is Key To His Character (Inuyasha)
Half-human, half-yokai, and all attitude: that's Inuyasha, more or less. Inuyasha's the product of Toga, a proud and renowned dog yokai, and a human woman named Izayoi. Set primarily in the past and in a parallel universe rife with mythology and magic, the world of Inuyasha is colorful but surprisingly sinister at times.
Despite or because of his half-yokai nature, Inuyasha himself is brash but good-hearted, and his two halves form a solid, albeit traditional shonen hero.
4 Fans Will Never Forget Nina Tucker's Final Fate (Fullmetal Alchemist)
It seems unkind to mention Nina and Alexander, but there's no denying that the pair become one of the most horrifying human-monster hybrids in anime history. Even today, few characters are as loathed as Nina's father, and for good reason.
Whenever Shou Tucker, a State Alchemist, is threatened with the loss of his alchemy license, he resorts to using his family members as part of his experiments. First, he makes a chimera by transmuting his wife together with another animal. Later, after the Elrics come to know Shou's daughter Nina and her dog Alexander, he splices them into one tragic, horrifying creature.
3 Rei Is A Human-Angel Hybrid (Evangelion)
If Rei Ayanami seems perpetually gloomy, she's certainly got her reasons. As the first of EVA pilots, Rei comes across as disaffected and melancholy, an enigma to Shinji and Asuka. In truth, Rei's aloof nature has a lot to do with not just her upbringing, but her very genes.
Rei is actually an artificial human, a clone, and far from the only one of her kind. Gradually, the audience learns that Rei harbors a shard of Lilith, the Second Angel. In a sense, she's not so different from Kaworu, but her origins, like many aspects of Evangelion, feel deliberately convoluted.
2 Snake's Parentage Is Hard To Fathom (Black Butler)
Suspension of disbelief is a requirement for most otaku, and part of anime's appeal is the way the medium isn't afraid to be outlandish and unbelievable. Yes, there can't be explosions in space or superpowered teens, but where's the fun in admitting that?
Even given this, Snake of Black Butler is a half-human that beggars belief somewhat. Apparently, Snake, the Phantomhive footman, is the son of a human and an actual snake. How this miracle of bizarre conception could have happened isn't clear, although Snake was cruelly brought up in a freakshow in his early years.
1 Kaneki's Organ Transplant Complicates Things (Tokyo Ghoul)
Ken Kaneki is a protagonist that has often divided fans. Some viewers found Ken's initial characterization as a cowardly boy unpleasant, while others found him realistic and relatable. As Ken comes into his Ghoul abilities, some fans found him cool as hell, while others felt only whiplash, unconvinced by the gap between his alter-egos.
Ken really does have two distinctive halves. He was human, but after ghoul organs are transplanted into his body, he becomes something that's neither one thing or the other. This contradiction seems all too fitting in a show that can't decide on what story it wants to tell.