Ooyuki Umi no Kaina

The "boy-meets-girl high fantasy" is set in a world where land is being swallowed by the encroaching Great Snow Sea. Humanity ekes out a harsh life above the Tenmaku (a wordplay on the Japanese word for tent) that stretches from the roots to the tops of giant Orbital Trees. The story centers around Kaina, a boy who lives above the Tenmaku, and Ririha, the princess of the small country Atland in the Great Snow Sea.