Kaina of the Great Snow Sea

Humanity’s remnants struggle to survive above the planet atop giant orbital spire trees, safe from the danger below. Rendered unlivable, the Great Snow Sea has turned the world into a no man’s land. While out hunting, young Kaina stumbles upon an unconscious girl who’s floated up from the surface. The discovery of this trespasser brings new hope for mankind’s future - and unimaginable danger! (Crunchyroll)