Long ago in a distant land, I, Aku, the shape shifting master of darkness, unleashed an unspeakable evil. But a foolish samurai warrior wielding a magic sword stepped forth to oppose me. Before the final blow was struck, I tore open a portal in time, and flung him into the future where my evil is law. Now the fool seeks to return to the past and undo the future that is Aku.
looking back on it, this is somewhat close to the main story of KH.