Kaina of the Great Snow Sea (大雪海のカイナ) is an original Japanese anime television series created by Tsutomu Nihei and animated by Polygon Pictures to commemorate the studio's 40th anniversary. The series aired from January to March 2023 on Fuji TV's +Ultra programming block. A manga adaptation with art by Itoe Takemoto was serialized in Kodansha's shōnen manga magazine Monthly Shōnen Sirius between February 2022 and June 2024. A sequel anime film titled Kaina of the Great Snow Sea: Star Sage premiered in Japanese theaters in October 2023. Crunchyroll holds the license of both the manga and the anime.
Plot
Kaina lives on a world covered in an organic membrane called the Canopy, created by massive Orbital Spire Trees. Far beneath the Canopy at the foot of the Orbital Spire Trees lies the endless Snow Sea, where Princess Ririha and her country of Atland struggle to survive against the cold and the rival nation of Valghia. When Ririha travels to the Canopy in a desperate bid to save her country, she is rescued by Kaina, setting in motion events that will have the pair travel the world to uncover its secrets.