To Your Eternity

An omnipotent narrator casts an orb of light to the Earth, watching as this entity copies the shape of a rock and then, many years later, mimics the moss on a rock. When a wolf dies beside the moss, it evolves, taking on the creature's shape and gaining movement for the first time. As the wolf, the orb observes the dead wolf's owner, a young man who lives alone on a frozen tundra, and accompanies him on his journey to reunite with the rest of his townspeople, who crossed the icy wasteland years before in search of a more bountiful country. The time the orb spends with the boy leaves a mark on the entity as it observes, mimics, and bonds with the boy and then the other creatures it eventually comes across—all while transcending death and living for time immemorial. <em class=de-emphasized>(from manga)</em>

Synopsis from Anime News Network