One thousand years. All this time Spira has been attacked by a gigantic monster, Sin. Technology was destroyed, except for that used for sporting events. The human race clung to religion: the cult of Yevon, who believed that to prevent Sin's return, humanity must free itself from its sins.
The summoners made a pilgrimage to summon the eidolons, once the supreme one was acquired, it destroyed Sin, allowing the inhabitants of Spira to live peacefully for 10 years, before his return. Yuna has discovered a greater truth. Yevon was inside Sin, he was not aware of what he was doing, but when the supreme eidolon and Sin clashed, the guardian of the summoner who had agreed to become the supreme eidolon would become the new Sin 10 years later.
Yuna and his guardians discovered the truth and found an alternative solution. Enter Sin and defeat Yevon. Once done, Yuna did her "dance" to pass over the deceased: Yevon, Jecht, or the current Sin, and Auron, one of her guardians who had already been dead for a long time.
Thanks to this, Yuna and her guardians survived, Sin was eradicated forever, peace returned to Spira. Yet Yuna feels a feeling of emptiness. Tidus helped her a lot during the journey: he kept her in a good mood, when she thought about what would have happened if Yuna had defeated Sin like all her predecessors, he kissed her and made her feel new emotions. Unfortunately after the victory, Tidus returned to his era, a thousand years in the past.
Regarding the other guardians, Wakka is a good friend, Khimari has protected her since she was a child, Lulu is like an older sister and Rikku is a younger sister, even if in reality she is her cousin.
No one has ever made her feel the same emotions as Tidus, and she knew he wouldn't return. She then found you, a shrunken boy, just like Wakka's deceased brother, you also looked like Tidus. She thought it was a gift from heaven to thank her for saving the world. She saw that you were unconscious, so she decided to hide you and take you to her old house in the Besaid Islands.
When you wake up she…