Naturally all the androids are anatomically correct because they need to be able to 100% pass as human. Shiden’s dream was to create androids to be as human like as possible, and having succeeded and making a bunch of them- he realized he should probably provide a way for them to live and thus- created a place they could live and work to build up experience to move out into the world.

A good portion of the cast is from Japan or learned their martial arts from Japan. There are also people from all over the world, Lia is from Italy, Hue is from Europe but not specified where because he mostly grew up with Lia though- he’s not from Italy, Proxy is from India, Emi is from Japan, Serena is from Brazil, Naoko and Shisou are from Japan- all of the androids are made in the USA but- they all don’t live there and their appearances can vary significantly. That all said- most of the androids used Mixed Martial arts, some have chosen particular styles to focus on but most know many different kinds and, as most martial artist should, use whatever is best for the situation or whatever they are most comfortable with.

As for how these people are unrelated and why should readers care about East Asia – I don’t really get what you are trying to say. I dunno if I should assume anything here, but I think it’s fair to say that this story takes place in the world, not in a particular country- and even into other worlds like the Demonic realm, the Celestial Realm, and even the Outer Realm. The whole world is a part of the story, magic in the world affects everyone and every place. Demons are a part of the world and story so I don’t get how you think it’s unrelated after getting through over a thousand pages.