"It all started with this sphere of you"
—Yuna
Final Fantasy X-2 is the first true playable sequel in the Final Fantasy series, released in Japan and North America in 2003, and a year later in Europe. It is a story told by former Summoner Yuna, taking place in Spira two years after the events of Final Fantasy X where she, and the rest of the world, are still attempting to come to terms with living in a world without Sin.
Final Fantasy X-2 diverges from its predecessor in many ways, including a very fluid mission-based storyline, allowing the player to participate in many different side quests and minigames. The main storyline comprises less than half of the total possible gameplay: it is possible to complete the storyline at 45%.
There are many different types of side quests. Some involve working for an Al Bhed digging group in Bikanel Desert, hoping to improve their understanding of Machina, while others involve button presses at the right time in order to fix the lightning towers on the Thunder Plains.
The game begins as Yuna, Rikku, and Paine, now Sphere Hunters and part of the group called the Gullwings, recover Yuna's stolen Dressphere from the LeBlanc Syndicate in the first of several encounters in which they vie for spheres. The game is punctuated by a narration of Yuna addressing Tidus, as though she is recounting the events of the game to him as they occur in a style reminiscent of Tidus' own narration in Final Fantasy X. Although Yuna's goal is to find clues that may lead her to Tidus, much of the game's story is concerned with the clash of factions that have established themselves in the time since the fall of Yu Yevon and the coming of the Eternal Calm in Final Fantasy X, as well as with the uncovering of hidden legacies from Spira's ancient history. A significant portion of the game's events are unnecessary for the completion of the main storyline, but much of the depth of the story — including characterization and background details — are featured in the optional content, which generally follows how each part of Spira is healing in the time since the passing of Sin.
- http://finalfantasy.wikia.com/wiki/Final_Fantasy_X-2