Spira - Once upon a time it was a world of prosperity, sustained by an advanced civilization of machina (or machines).
Then, one thousand years ago, Sin came. This immortal menace brought perennial destruction to the land and slowed advances to civilization. The teachings of Yevon offered solace to Spira’s terrified people, but also forbade the use of machina. Still, most people were willing to sacrifice progress for a sense of security, and civilization eventually came to a standstill.

Summoners emerged as Spira’s only hope. They alone were able to stop Sin—if only for a little while.

On the day she becomes a summoner, Yuna, a girl of seventeen, meets him. The young man claims to have come from Zanarkand, though that city was supposedly destroyed a thousand years earlier.

Hearing his claim, Yuna knows this is no chance encounter. Her father, Braska, was a summoner before her. Jecht, a man who served as his guardian, also claimed to have come from Zanarkand.

The next day, Yuna and her own guardians—Kimahri, Wakka, and Lulu—set out on a journey to defeat Sin. He comes along, too, and before long he becomes one of Yuna’s guardians. Others join them: a man named Auron who guarded Braska and an Al Bhed girl named Rikku. The pilgrimage continues.
Yuna and her entourage witness much. Operation Mi’ihen is launched in an attempt to stop Sin with machina, but it fails. Seymour Guado, a maester of Yevon, reveals machinations of his own. Finally, Yuna and company arrive at their destination, the sacred ruins of Zanarkand. It is here that they were to learn the one and only way to defeat Sin: the Final Summoning.

But Yuna learns something entirely different. Sin cannot be truly destroyed using the Final Summoning. Not now, not ever.

Rikku’s father, Cid, takes Yuna and her friends aboard his airship. They begin a new journey, this time in search of another way to destroy Sin. After uncovering the truths and fallacies behind Sin and the teachings of Yevon, they finally succeed in vanquishing Sin.

However, that victory meant he would vanish. A heavy price is paid, but Spira finds peace and freedom from the terror of Sin at last.

Filled with the many memories of her journey, Yuna speaks to the people of Spira:

“The people and the friends we have lost, or the dreams that have faded... Never forget them.”

Two years past. Sin is defeated and the world is a better place, but is it? Two seperate groups, the Youth League and New Yevon have taken their rivalry too far and are causing trouble in Spira. Meanwhile, Yuna has been living peacefully in Besaid. However she is troubled and restless. Then one day, Kimahri finds a Sphere in Mt. Gagazet and Yuna believes that the imprisoned man featured in the Sphere is him!

Yuna is given a new hope and sets out with Rikku and the 'Gullwings' disguised as Sphere Hunters to find out if it really is him.

Along her journey across Spira, Yuna tries to make peace between the Youth League and New Yevon, but it doesn't turn out very well...

Causing more disturbance is the Guado and the Ronso, almost at war with each other for Seymour Guado's actions. Only Kimahri and Yuna are trying to stop the fighting, but will they succeed? As Yuna, Rikku and Paine collect Spheres to help them bring a new calm to Spira, a new group of Sphere Hunters try to stop them, LeBlanc, Logos and Ormi. As Spira slowly spirals into doom once again, a new enemy appears, Vegnagun... Will Spira ever stop fighting with itself?

If it is him, Yuna might be able to see him one more time. If not, Yuna will probably never see him again.

No matter what the truth may be, the answers she finds may change things forever.