The South is a stand in for the US, Sentan Island for Japan, and the North for China.
No, Sentan Island is Japan, but the South is China and the North is Russia.
The North and South were once a single country but split due to scientific and religious views.
Had Guruichi gestated first, Haru would have fallen in love with him instead of Akiyuki.
The Xam'd and human forms are the next step in earth's evolutionary path.
Had Akiyuki not given away his armband, Midori would have received the hiroku.
Prios is a Xam'd who has obtained full instrumentality with her hiroku.