Part 1: Backstory Primer!You scored Key Item Backstory Primer!
This is Yuna. She's the main character of this game, and arguably of the prequel as well. Two years ago, she, a cute boy, and five RPG protagonist misfits went on a pilgrimage to defeat Sin, an invincible town-destroying monstrosity. The pilgrimage would ultimately cost her life, and Sin would inevitably return, but she was prepared to make that sacrifice for even a few years of peace. But when she discovered that she would also have to sacrifice one of her comrades, who would be cursed to become the next incarnation of Sin, she rejected her fate, demolished the religion of Yevon that perpetuated the cycle of death and sacrifice, and destroyed Sin forever.
I like Yuna's characterization in this game. I think it flows very organically from her growth in the prequel, and the game doesn't try to rehash her arc. She also behaves the way you'd expect a teenage girl who just left the Church of the Ritual Suicide to behave. She's still got her stubbornness and her sense of duty, but she's shedding her naivete, questioning common wisdom, and letting herself be a little selfish now and then.
Rikku is the other protagonist transplant from the prequels, and the one that suffered more in translation. In FFX, she was fifteen and obnoxiously perky, but also a clever and serious schemer. Her major plot arc was a plan to kidnap all the summoners to protect them from sacrificing themselves to fight Sin, which led to her fighting and/or spying on the main party for a good portion of the game. Rikku is also Yuna's cousin and an Al Bhed, which came into play with a heavy-handed metaphor about racial tolerance.
Somewhere in the intervening two years, Rikku picked a fight with a wood golem made entirely from branches of the Stupid Tree. She now exists almost entirely as comic relief, making up nonsense words and falling on her ass a lot. I'd rather see it happen to Rikku than Yuna, but I wish it hadn't happened at all. She still acts as Yuna's protector and confidant, but, now that the threat of Sin has been lifted, she's a much worse influence than she's ever been.
The new main character, Paine, also sometimes known as Squall With Tits. Paine's backstory is woven into the plot with an admirable subtlety, as most of the salient bits don't get revealed without completing sidequests, so someone steamrolling through the main game can miss a lot of her characterization and motivation. Paine is straightforward and taciturn, and uncommonly driven. She's the first to speak up if she feels that time is being wasted or when the group's not actually hunting spheres. Early in the game, the three main characters haven't been together very long, and Paine is like that grizzled buddy-cop movie archetype who keeps her new partner at a distance at first because she's still dealing with the loss of the last partner. I think Paine is ultimately very likeable, even if she is getting too old for this shit.
A thousand years ago, during the war that destroyed the great city of Zanarkand, its residents were transformed into living statues called fayth which can manipulate spiritual energy. Some of them were used to power the aeons summoned by Zanarkand's summoners, including the first Sin. The rest were used to generate a running simulation of a Zanarkand unspoilt by war, without summoners or weapons.
Tidus, the aforementioned cute boy, is basically Holodeck Moriarty. He was born in the simulation of Zanarkand, got pulled into the real world by Sin, and started following Yuna out of nothing better to do. He was also the only member of the pilgrimage who didn't know that Yuna's mission was a suicide mission, which makes for some hilariously awkward moments when you play the prequel a second time, and it was his boundless optimism that inspired Yuna to reject the false hope the world had survived on for generations. When Sin was defeated and the fayth were all laid to rest, he faded away and was posthumously knighted Sir Not-Appearing-In-The-Sequel. But, if the prequel taught us anything, it's that death is a temporary setback at best in this universe.
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