Why do Okinawans have different features?

I'm half Okinawan and pride myself on it (I really don't care about my other mixed stuff that much). I get my Okinawan blood from both side of my family. I also have family members who are Japanese and I can't help but notice there is a big difference between us. For example Okinawans have bigger eyes. I'm a little confused to why we have all these different features compared to other Asians that we are supposedly related to (like Japanese and Chinese [or that's what I read, I'm not sure if it's true]). Is there some type of climate related reason or ??? By the way, from my the way I was raised, we are strictly Okinawan (not Japanese [my family gets offended if you say they are Japanese])