Ixion Saga DT is absolutely not the kind of show out of which I’d expect anything resembling decent trans rep. It’s essentially an isekai parody — the protagonist, Kon, is dropped into a fantasy world from in front of his computer in Tokyo, and winds up tagging along with a young princess traveling to an enemy nation to get married and stop a war. It’s the sort of show where every character has about three personality traits — Kon’s are that he’s a pervert, an idiot, and an otaku — and half the humor comes from poking fun at how straightfaced the setting is. Kon’s goal is to lose his virginity. The “DT” in the title officially stands for “Dimensional Transfer,” but it’s also short for “doutei” — the Japanese word for “virgin.” That kind of show.
In fact, when Mariandale — the princess’ maid and one of the main party members — is introduced, it’s about as bad as I would have expected. She’s initially presented as a beautiful girl, but when Kon starts cozying up to her, the princess — Ecarlate — says “that’s a man.” Kon is, of course, shocked; Marian responds by saying “you got a problem with that!?” in a deep voice and forcing his hand onto her crotch.

Other than this one time, Mariandale is generally referred to — both by herself and others — as a newhalf. This is what’s called a wasei-eigo term — it’s derived from English, but exists only in Japanese. As far as I can tell, it mostly refers to someone who has both breasts and a penis, usually a trans woman.¹ It’s translated in the official subs on VRV as “transsexual” or just “trans” — I fully approve of this choice, but the actual associations with newhalf are a lot closer to “sh*male.” It’s offensive, or at least tasteless, and unless the connotations were a lot different back in 2012-2013 (they may well have been, it’s hard to look up this sort of thing), it’s closer to the sort of term one would associate with Marian’s introduction than the way she’s presented most of the time.
Thankfully, it’s all uphill from there, though I suppose it could hardly be downhill. The thing is, if you just ignore that first interaction, Mariandale is a character whose representation I would happily describe as “fairly good.” (I also found the show as a whole rather charming, despite my dismissive tone in the opening paragraph. I wouldn’t recommend it to just anyone, but I wouldn’t advise against watching it, either.)

Here’s the thing — the fact that Marian is trans is one of her defining characteristics, and it’s played for laughs more often than not. But Ixion Saga is a show where every character has 2-3 defining characteristics, and all of them are played for laughs more often than not. And yes, the jokes can be in questionable taste — for instance, at one point the main party goes to karaoke to try and cheer up Ecarlate, who has a tendency to run rampant when she’s in a bad mood. It turns out the best way to amuse her is self-deprecating song choices — Marian’s is about being trans, is sung as a duet with herself, using both her “male” and “female” voices, and includes the line “my dynamite swings freely.” Whether one finds this funny, tasteless, or both is really a matter of opinion. (I’m in the “both” party.) This is a particularly egregious example, though — for what it’s worth, a lot of of the jokes regarding Marian’s gender are about Kon overreacting.
Speaking of which, it helps a lot that for the most part, Kon is the only one who cares even a little that Marian is trans. There’s an episode centering around her fairly early on in which the party goes to the beach — when a couple of guys hit on Marian, Kon outs her out of spite, and is surprised when the guys aren’t the least bit put off. In fact, Marian turns out to be hugely popular with both guys and girls, because she’s basically perfect. Neither Ecarlate nor the party’s other member — a muscular, cat-loving man named Sainglain — even really understand why Kon is so bothered by it. Sainglain says there’s a reason for her living as a woman, though, and proceeds to go off on a ridiculous story about taking over her family’s martial arts style; when it turns out to have nothing whatsoever to do with her transitioning, Ecarlate takes over and goes off on an even more ridiculous story about a dead lover who Marian is endeavoring to live as. These both turn out to be completely made up for the sake of messing with Kon, obviously. The reason Marian gives for living as a trans woman is “because I want to, of course!”

I’m of two minds about this. On one hand, it’s a nice expression of gender euphoria when transness is so often associated with dysphoria and unhappiness with one’s body, and it makes a lot of sense considering how unselfconscious Mariandale is about being trans. It’s clear that it is something she enjoys, and moreover, that she enjoys being trans rather than desiring to be cis, which is something that doesn’t show up much in media. Being trans is great. Taking something that was forced on you without your consent and shaping it into something new and unique and transgressive is euphoric. It’s the way society treats trans people that sucks — and the society of Ixion Saga doesn’t seem to mind. (It’s implied that marriage for trans people is complicated, but that’s about it.)
On the other hand, it kind of leans into the rhetoric that being trans is a choice, rather than something innate. This in turn is used to argue that no one is really trans — trans women are perverted men, and trans men are self-hating women. I’m probably overthinking this, especially considering that she specifically says she’s a woman “in her heart,” which is the go-to Japanese phrase to indicate transness. It’s not like they’re saying it’s an act or anything.

In the end, I’d describe the handling of Mariandale’s gender as clumsy, but not bad. Everyone accepts her as female — as Ecarlate’s maid, Marian changes clothes, bathes, and gets a massage with her without anyone batting an eye, which is absolutely wonderful to see. Even Kon calls her “nee-san,” or “big sis.” There’s a moment where the party needs water “drawn by a pure maiden” for a ritual, and the water Marian draws doesn’t work — however, the ritual is kind of suspect to begin with, and considering how popular she is, it seems likely she’s not a virgin. Overall, she’s beautiful, popular, smart, a great cook and an even better fighter and markswoman — we’re clearly meant to like her and perceive her as female. Of course, you still see a lot of people calling her a tr*p and such, because anime fans are the worst.

It’s also worth talking about KT in the context of transness in Ixion Saga, even if she’s more gender non-conforming than genderqueer. KT is a member of Incognito, something of a rival party to that of Kon and his group, and for most of the series, she can be presumed to be male. Sort of. KT’s gender is vague as hell from the get-out — she’s treated as a man by everyone around her, and seems perfectly happy with that, but in her romantic fantasies with Incognito’s leader Erecpyle she’s clearly female-bodied. She also uses the gender-neutral pronoun “watashi” and is voiced by a female VA, albeit one who more often than not voices male characters. At one point, Incognito gets naked in an attempt to distract Kon — KT is the only member who doesn’t, though no attention is ever brought to it. Later in the episode, Incognito dresses up in ballet outfits, and her build appears masculine. (Ixion Saga is a weird show.) She has a tendency to speak in a very feminine manner while drunk. Her official character profile doesn’t gender her, per say, but implies that she’s male more than female.
In episode 23, we get a proper explanation, when she outs herself in a fairly casual manner by mentioning that she attended the same (all-female) school as another Incognito member’s ex-wife, and explaining that she was presenting male because she wanted to fit in with the rest of the team. Her teammates…are not surprised. Well, Erecpyle had no idea, but other than him. They all knew, or at least suspected, that KT was AFAB — all they say on the matter is “you’ve always been one of us,” which is very sweet. This gels nicely with the sense that the universe of Ixion is more trans-friendly than our own — it makes sense that they’d respect her choice to present as a man without seeing any real need to question it.
Honestly, KT is the sort of character who I’d be more inclined to read as genderqueer — albeit not confirmed as such by canon — if not for Mariandale, who is canonically trans. KT specifically says she’s a woman, and gives a reason for why she presented male that isn’t “because I wanted to.” Conversely, Marian says she was born a man but is a woman in her heart, and presents female because she’s female. I wouldn’t argue with anyone who did read KT as genderqueer, though — there’s a lot of evidence to support it.
As for how to improve the representation — I’m hesitant to say “don’t make Mariandale’s gender into a joke,” both because that would require a lot of changes throughout the show, and because I don’t think there’s anything inherently wrong with it. One of the things I appreciate about Luca Esposito from Astra: Lost in Space is the light, casual way his gender is handled. Being trans is a type of lived experience, and just like any other lived experience, there are things about it that are funny. Some of the jokes are just offensive, though — there’s a point where Sainglain and Marian are revealed to be leaders of two revolutionary groups, with Sainglain’s being for “muscles and cute animals” and Marian’s being for…trans and gender-nonconforming rights. Most of the members of her group are stereotypical okama. It’s galling to see a genuine civil rights struggle reduced to a gag.

Other than that — change Mariandale’s awful introduction, for one. Instead of Ecarlate outing her — and calling her a man in the process — she could just say “I’m trans, FYI” when Kon starts getting cozy with her. That way, she’s not misgendered, she doesn’t come across as a predator, and Kon freaking out is more obviously an overreaction. The use of the term newhalf is also questionable at best — I’m not sure what the generally accepted term was in the trans community at the time, but there had to be a better choice.
I don’t think KT needs to be changed at all. I like the extreme ambiguity of how she’s presented and how she’s unquestioningly accepted by the rest of Incognito. It’s very cute. I just hope she can get over her crush on Erecpyle, since he’s happily engaged to someone else.
Overall, I would describe Ixion Saga DT‘s depiction of transness as “confused, but positive.” It’s far from perfect, but it’s also a hell of a lot better than I would have expected from this sort of show.

¹ – At one point, Kon calls his rival Erecpyle — a man whose testicles have been removed — a newhalf; I have no idea what to make of that.