A world blanketed in an endless and ever-growing ocean of snow. The people eke out a living, either huddled around the roots of enormous trees dotting the surface, or high in the canopy, which spreads over the planet's atmosphere.

Kaina returns to the icy Canopy, unsure of what he should do next. He and Liliha have brought peace to Atland and Valghia through an alliance. Now supplies run low, and the people need answers. Kaina, Liliha, and their small party set out to cross the snow in search of the great orbital spire tree. This is the first step to saving their people.—Crunchyroll

Peace has been forged between Atland and Valghia, but the rising threat of the Snow Sea remains unabated. Kaina and Ririha's quest isn't over yet. With a new ship at their disposal, they embark on one last journey past the fabled great oceanic trench, towards the central orbital spire tree, and into the roots of the mysteries that will determine the fate of their dying planet.—Anime News Network