"Long ago, our ancestors struck a pact with the gods in exchange for a gift. Thanks to that, life in the frozen lands became somewhat easier. But when sea monsters suddenly appeared, the waters were stained with their black blood, and the land that had been blessed by the gods was torn asunder." Aki, a young boy from a clan capable of manipulating ice, must pass a village ritual to be recognized as a true adult. Though he has failed time and again, he faces the challenge once more, supported by his brother Yako, a skilled hunter. However, Aki had no way of knowing: on this day, his life would change forever.

Cross Heart is a love story between Haru, an energetic and determined teenager, and Kotomi, who is always shrouded in an aura of sadness. Haru watches her curiously until something happens that makes her act. Little by little Kotomi is sheltered by Haru's warmth and affection making her feel happy again, while Haru almost inadvertently begins to fall in love with her. Will Kotomi be able to confess her biggest secret to Haru and get rid of the pain that plagues her heart?