Ys(イースĪsu) are two different anime series, both of which are based on the video game series Ys. The first series (often referred to as "Book I") spans seven episodes and covers the general plotline of the first game of the series, Ys I: Ancient Ys Vanished. The plot centers on Adol Christin as he journeys to the island of Esteria in search of adventure. Upon arrival, he learns that a dark priest known as Dark Fact has been tearing the island apart in search of six mystical tomes of power, the Books of Ys.