Celestia

The "Great Invasion" originated from the sea. It moved north across the mainland. Many fled, while some took refuge on a small concrete island called Celestia, built over a thousand years ago. Now cut off from the mainland, Celestia has become an outpost for criminals and other misfits, as well as a refuge for a group of young telepaths. Events push two of them, Dora and Pierrot, to flee the island and set sail to the mainland. There, they discover a world on the precipice of a metamorphosis, though also a world where adults are literally prisoners of their own fortresses, unintentionally preserving the "old world" at a time when a new generation could guide society towards a better humanity.