Humans (Notes)

Humans that appear in Notes can be divided in two categories: =Unmodified humans= Humans whose body build was not modified to accommodate the change in environment. Because of that, they can't breath the atmosphere without medications or air purification devices. They are considered nearly extinct, and Gun God is in fact mentioned to be the last of his people.
 * normal, unmodified humans
 * enhanced humans

The only advantage they might have is the fact that their bodies reject Gin, so they are unaffected by weapons that target Gin specifically.

=Enhanced humans= Physically similar to unmodified humans, the only difference being that their bodies can survive in toxic atmosphere and are not affected by Gin. That doesn't mean they can use Gin as a weapon in the way A-Rays can, though. They are trying to rebuild their civilization that was nearly destroyed in the Great War with the A-rays.

Ether Liners
Also known simply as Knights.

Gin from he atmosphere sediments in human bones during their lives. Knights are humans that were able to shape their own bones into powerful weapons known as Demonic Swords. Due to being made out of Gin, Demonic swords can have various effects and a Knight wielding it can fight with a member of A-rays on equal ground.

=References=
 * 'Notes' translation by Evospace, edited by Raeinus, from Beast's Lair