POC representation

[Iscah]

They probably just chose their fantasy-Europe as the main setting because it would go down better with Japanese audiences. Also, European people commonly have brown/black hair and brown eyes, yet you don’t see this in the scions. They’re pushing that pale-hair, pale-eyes, pale skin thing that is favourable in Japanese media.

That doesn't mean the characters are meant to be Japanese though. But the implications of that "stateless" character design means that you can't tell the difference between "anime character who is Japanese" and "anime character who is English" because they'll come out looking the same due to the art style, so you have to rely on other cues besides the characters' appearances to work out the intended equivalent.

The logic that "they're meant to be Japanese because Japanese people make their Japanese characters look indistinguishable from European characters" doesn't hold. It just means you can't tell which one is intended by looking at a picture of the character without context.

Nothing about the characters seems Japanese. Not their names or the way they dress or the place they live in. They write in an English-derived alphabet. They are actively contrasted with the Japanese-inspired Doman and Hingan characters.