In the chronology of the series, Skyward Sword is a prequel to Ocarina of Time. The incarnation of protagonist Link that appears in the game was born and raised in Skyloft, a group of islands floating above the clouds. Leading an ordinary life there, Link discovers the Skyward Sword one day, which leads him to another, previously unknown land beneath that is ruled by evil forces. Using the sword to travel back and forth between sky and land, the mystery of why the two worlds became separated is gradually revealed to Link. The Skyward Sword becomes the Master Sword at some point in the game, and assumes the form of a female figure while giving Link advice. Producer Eiji Aonuma has stated the game's plot to be comparable to a school drama. Unlike in previous series instalments, Zelda is not a princess in Skyward Sword, but a childhood friend of Link. Throughout the course of the game, Zelda disappears and Link has to find her. He is opposed on his quest by the Demon Lord Ghirahim, a mysterious and powerful figure who rules the surface world, who wishes to kidnap Zelda for unknown purposes. Skyward Sword connects to the story of Ocarina of Time, and elaborates on Ganondorf's origins.