Ruto is a princess of the Zora race and daughter of King Zora. In Ocarina of Time, she was the keeper of the Zora Sapphire, a Spiritual Stone needed in order for Link to unlock the secrets of the Temple of Time. However, when Link sought her out, he found that she was accidentally swallowed by Lord Jabu Jabu. Link then attempted to enter Lord Jabu Jabu's belly by baiting him with fish. He then traversed through the giant fish's intestinal tract in order to rescue the Zora princess. After the mission, Ruto thanked Link and rewarded him the Spiritual Stone. However, she also ended up believing that they were engaged for marriage.
Seven years later, as Link emerged from the Sacred Realm, he learned that he must embark on a journey to obtain the Medallions of the Six Sages. One of the Medallions rested in the Water Temple. As it turned out, it was then revealed to Link that Ruto is the Sage of Water. She displayed disappointment for his long absence but understood that they could not be together anyway. Ruto then bestowed upon him the Medallion of Water so that he may continue on his journey.
Princess Ruto has a bit of a spoiled personality. She initially belittled Link on their first encounter and then had him carry her around when they were escaping Lord Jabu Jabu's belly. In the end of that ordeal, she then became deeply infatuated with him and hoped that they would marry. However, since she discovered that she was the Sage of Water in her adult life, a mature side of her shined out, and she ended up supporting Link on his heroic adventures.