From the introduction:
Within a distant fortress lived a Sorceress by the name of Cia, charged with observing and maintaining balance between the three pieces of the Triforce. Through her magic and duty to observe, she was able to see throughout space and time.
Eventually, she would feel her heart stir with a powerful affection for the reincarnating Hero of Time. It would be those same feelings of affection that birthed an ugly jealousy for Princess Zelda, who was destined to be reborn with the Hero of Time forever, their destinies intertwined.