Anime adaptation of part three of the Honzuki no Gekokujou light novel.

After a covert mission goes wrong, Mobile Suit pilot Amuro Ray and his comrades are stranded on a remote island. The battalion was sent to a land called the Island of No Return to clear off any enemy forces, only to find a group of children and an enemy mecha attack. Now Amuro must find a way for them all to escape this mysterious land, but not before meeting a strange man—Cucuruz Doan. (Source: Crunchyroll)

Confined in the castle tower by her father, princess Arete spends her days watching the world outside her window. Sometimes she seeks out to watch the common people at work. The knights of the kingdom compete for the right to marry her and rule the land by competing to see who can find powerful magic objects made by a long dead race of sorcerers. Arete wants none of this. She longs to meet the common people and travel to exotic lands she has only seen in the books she keeps hidden under her bed. One day the sorcerer Boax arrives in a fantastic flying machine and offers to take Arete as his wife and transform her into a proper princess. (Source: ANN)

Second part of Kyoukai Senki.