I get the impression that the corporate territories are just one part of a much wider human civilisation, with many powerful nation states like Zairon, it's just that Zairon happens to border the corporation. IIRC there's also been some mention of a League of independent worlds which is implied to be able to collectively rival the corporations in terms of military power.
I'm not asking for an in-story explanation, I'm questioning why the creators chose to illustrate Japanese culture in this way. What I'm saying is, back at the beginning of the creative process, if the thoughts running through Mallozzi's head included "I want a corporate dystopian future" and "I want an homage to anime," why did he end up making them so separate from each other, when anime is so rich with corporate dystopias of its own?
As for why Zairon is the way it is: monarchies typically couch themselves in ancient traditions an regalia. Mostly to hearken back to an age of perceived greatness. It's not that unusual.
But it's pretty weird for a creator's mind to go there when thinking of Japanese culture and anime, because Japanese culture has been aggressively forward-looking and innovative for 150 years now, which is how we've gotten so much of our computer and entertainment technology over the past few decades. It just feels like the creation of a white guy who likes an "exotic" foreign entertainment genre but has a poor, superficial grasp of the actual culture underlying it.
Not to mention that, again, it doesn't bear much resemblance to most of the anime I've seen, so I'm really puzzled about what specific anime he's trying to emulate here.
The argument that it's just the imperial court engaged in historical cosplay would be more convincing if we saw more of Zairon culture beyond the palace and saw it portrayed as something more like, say, modern Shibuya District with its bustling crowds and giant flashing video screens. Something that represented the forward-looking side of Japanese culture as well as the traditionalist side, so it'd feel less like an outsider's simplified stereotype. Sure, we see their high technology with their spaceships and research lab and all, but it would help to see more of the everyday civilian culture, to show that all this kimono-wearing SCA crap is just an affectation of the imperial court. But since we hardly ever see outside the imperial court, it conveys the impression that this historical-drama rubbish is normal for Zairon culture, and that's what makes it feel stereotyped.
From a meta perspective: it's probably mostly just an aesthetic choice to distinguish this sovereign nation from the corporate authorities and to show non-western culture made it into space.
But non-Western culture is not just swords and kimonos and honor duels. That's a 19th- and 20th-century Orientalist assumption, that non-Western means backward and the West has a monopoly on modernity. Bull. Non-Western means Sony. It means NEC. It means Nintendo. It means bullet trains and emojis.
Mikkei is that modern Japanese (or maybe Chinese, allthough it does feel more Japanese to me) mega-corp in the Dark Matter world, a counterpart to US-feeling Ferrous, probably supposed-to-refer-to-Germany Traugott and Russian Volkov-Rusi.
Well, sort of. "Mikkei" does have a Japanese sound to it (evoking "Nikkei," the name of the best-known Tokyo Stock Exchange index), but it's a made-up word, and its representative is Commander Truffault, so it doesn't have any clear ethnic or cultural coding to it. Which is probably a much more believable way of showing culture in the far future than the self-conscious antiquarianism of the Zairon court.
As for the anime he is fan of, I'm not aware of all of it but he mentioned for example Cowboy Bebop and Code Geass. The latter he calls part of a "swords in space" genre.
That's odd. I haven't seen Code Geass, but Wikipedia says it's set on an alternate-history Earth in the 2010s, and going by online images, it has a lot of mecha suits/giant robots too. Cowboy Bebop is in space, but it's more guns, jazz, gangsters, and cyberpunk than swords.