The manga takes place in a post-apocalyptic world of some kind.
With the underground city ruins under Octopus, and the underwater structures in the Parallel stories that look very much like skyscrapers, this troper wonders if something terrible happened in the past. After all, the Astarian calendar is only in the 300s... And it could explain why +Anima exist to help children survive. The Anima are all Eldritch Abominations from the result of humans and animals breeding.
How else would you explain the different kinds of animal characteristics?- Jossed. +Anima are created when childen see animals during their near death experiance. It's said that anima is supposed to help child survive and will disappear when it's no longer needed.
