Ooyukiumi no Kaina: Hoshi no Kenja

Summary:

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. A chance meeting between Kaina, a youth from the canopy, and Ririha, a young woman from the surface, sets off a chain of events that will change the fate of the world.