In the manga +Anima (2001-2005), what is meant by the titular term is a human who possesses the secondary traits of a particular animal, like the wings of a bird or the strength of a bear. That sounds like a great premise for a superhero fantasy, but this series chooses to spin it a bit differently. Unfortunately for the +Anima, being so "different" isn't necessarily a blessing within a prejudiced society.
The series's four main characters are all +Anima with different animal bases. For example, Husky is a fish +Anima. Part-human, part-fish. So basically, a mermaid. ...Except, in this case, not a "maid."
Through childhood, Husky is raised to be little more than a sideshow act in traveling circus. This is sadly not an unusual practice within this fictional world, where there is great discrimination and dehumanization against +Anima as the unfamiliar Other. Catering to the public's fantasy-driven expectations of a "mermaid princess" for maximum profit interest, his naturally feminine features are exploited for all they're (monetarily) worth. He's dressed up in radiant pearls and a long flowing wig and placed in a tank to be gawked at.
Husky manages to escape from this demeaning role with the help of a fellow +Anima, from then on shedding his explicitly feminine disguise, but of course retaining his sleek and soft natural features that continue to grant him an androgynous vibe. However, not surprisingly, he isn't one of those androgynes who's comfortable with the ambiguity; because of his negative past experience, he remains uncomfortably averse to being associated with any kind of femininity in the future.
This backstory offers enough valuable perspective, on the good and the bad of androgyny in a social context, to be worth highlighting in itself... but what makes it even better to discuss is its potent connection to the larger relevant themes of the entire series. A series about characters with personalities that mismatch their facades.
Anthropomorphic characters exist in a similar symbolic vein as androgynous characters: expressing a combination of traits perceived not to belong together. Character designs that purposefully defy such expectations are always interesting, and often more deeply significant.
Cooro, the outgoing and happy-go-lucky protagonist, is part-crow, associated with omens of bad luck.
Nana, the young one who loves bright colors and cute things, is part-bat, associated with ugliness and dark.
Senri, the team's silent and sensitive pillar of strength, is part-bear, associated with aggression and fear.
The theme here is that the +Anima are rejected by society for assumptions about their bodies that don't genuinely define their character.
...That sounds familiar. That is, with regard to sex and gender.
Something that looks like a crow and flies like a crow doesn't necessarily conform to preexisting ideas of what a crow should be. Likewise, a male or a female body doesn't necessarily indicate any particular, standardized character, nor even does a perceivably "masculine" or "feminine" style necessarily reflect the same values you've learned to associate with masculinity or femininity. Romanticized ideas about supposedly inherent truths associated with visual motifs are dangerous to internalize, especially when applied to real live humans whose individual preferences can thereby be screened or overwritten by a stereotype.
In such a culture, discrimination and oppression can only multiply, because individuals will be taught to dislike "atypical" things about themselves, try to conform to the supposed norm, and thereby perpetuate negative sentiment. This phenomenon is observable through both the androgyny and the anthropomorphism in this particular story– first evident in Husky's shunning of femininity (not only does he hate being mistaken for a girl, but he even claims to hate girls in general, and initially shuns the affections of the very "feminine" Nana) and paralleled by many other +Anima who choose to isolate themselves from society or else conceal their animal traits, forced into guilt and resentment of their own abilities.
+Anima demonstrates how important it is to be able to distinguish natural reality from the imposed social stigmas that have come to define it. When there's someone (much like an androgyne) who doesn't "fit in" to a set of social standards, it tends not to be the fault of the individual but the fault of the standards for not recognizing the truth of diversity, and the shared humanity beyond whatever else appears on the surface.