hmm... i read back on the lore we've been given and it seems like they're a family with a lot of influence around okinawa, to the point they were even appointed as the point of contact with hoshijima, even when it was a confined land

in regards to their relationship with hoshijima, the label mizusaba gave his family is "mediators" and "point of contact", rather than protectors. when ryuseitai try to learn more about the hoshijima residents, mizusaba explains to them that they're just ordinary people with a unique religion, which sounds to me that he's speaking as an outsider of the group. he also mentions that he doesn't actually have connections with the hoshijima residents (save for konata). this is my own interpretation, but it implies to me that mizusaba's relationship with konata is more of a personal one, hence why he tends to try and help him.

that all being said, there may be way more to their backstory and origins that we still don't know. the farthest we know is that their grandpa was a feared pirate around okinawa (i tried to search where akira got this inspiration from, and only found one historical figure but not sure if that's where it's from... yet) who eventually settled down as he grew older. they also use a lot of okinawan dialect, and from my own interpretation, i noticed that ibuki sees himself specifically as an okinawan (with american influence) rather than a "japanese person" born in okinawa. what i mean by this is that there's a clear distinction being made here, even though okinawa is still a prefecture in japan.

i hope i'm making sense...... this was basically just me presenting the information we know so far, but also, just like you, i'm wondering what this means about their origins, because there is still a lot we don't know yet. it makes me want to find books on okinawa and learn more HAHA i'm so curious and intrigued.