I think the Imperial Radch trilogy is so fascinating to read through an asexual/aromantic lens because...
One of the gradual things you realise is that Breq just doesn't really seem to have any desire for sex or romance. A bunch of characters keep expecting her to be, think that's part of her motivation, but it isn't. She notes if someone is traditionally attractive via Radchaii norms, but otherwise doesn't seem to eeally feel anything herself (with the possible edge case of Chelar, which she can't seem to mention without including how big and beautiful she is.)
So, you go, okay. Half human, half-robot. Or human body possessed by a super powerful AI. That's why she's like that. It's the traditional ace robot trope.
But then you find out... Nope. Ancillary bodies experience everything human bodies do, which for 'some' bodies, means libido and lust and all that jazz. "I made sure [my bodies] were... comfortable," Breq says, in a short exchange that suddenly implies a whole lot of ancillary orgasms/masturbation.
No. It's just Justice of Toren One Esk Nineteen, aka Breq, who doesn't feel that attraction.
It's left a little ambiguous if that's something inherent to her body's physiology, or if this is a result of the whole grief-fueled-revenge-quest Thing she has going on (I suspect it's a mix of both). But nonetheless, that's coming up 'null'.
At the same time, it's not ONLY a consequence of Breq being an AI. She mentions, off-handedly, that she suspects that Medic also doesn't feel sexual/romantic attraction. So it easily side-steps that pitfall too.
So okay. That's the ace part. What about the 'aro' part?
Romance does absolutely exist in Radchaii society, but it looks quite different than in our modern day one. For example, polyamory seems to be the default, and Breq comments on a song about someone pining after a crush who's in love with another that it's "not a very Radchai song". Indeed, romantic pairings seem secondary to the most lauded relationship ideal in Radchaii culture: clientage.
Clientage doesn't really... map, easily, to anything in modern cultural norms. I guess I'd say knight/liege? The idea that you pledge yourself to a wealthy client, aiding them in some way, and in turn they support you. This seems to exist across a lot of sectors-- military, mercantile, artistic, etc. Musicals and stories about clientage are very prominent in Radchaii culture, and when priests strike, people complaining about the lack of clientage contract registration is up there along with birth and death certificates.
Seivardan wants to have Breq's clientage. It seems she partly assumed that's what things were building to, in book 1; she outright states that most of the crew assume she's "kneeling to" Breq in book 2. Yes, she wants sex from her as well, and arguably romance too, but that's the main relationship mode she is pining for.
But Breq isn't interested. So even for this in universe default relationship system, Breq's defaulting on it.
no. by the end of the trilogy she's settled into something extremely weird by the standards of both our culture and Radchai culture:
a 'i guess we'll call it platonic' polyamourous trio between herself, an ancillary lacking a ship body, the ship she captains which lacks any ancillary bodies, and Seiverdan, roleplaying as their intermediary fake-ancillary between them. absolutely fascinating.
THAT'S what i want from constructed queer worldbuilding