The religion of Yevon is the pinnacle of Spira's lifestyle. It is how the people accept the existence of Sin, and how they cope with it. Not only that, but Yevon is what guides summoners to defeat Sin - only to have it return a decade later. All in all, it's a giant hoax, but it's a giant hoax that everyone believed in; that is, until Tidus comes on the scene.

Sin is to stay until the people have atoned for their sins. What, exactly, are the peoples' sins? Were they really so bad to warrant the eistence of Sin? These are questions that few have asked. Tidus brings it up in conversation with Yuna, who is startled by the thought. "Ever since I was young, I never questioned it. But now that you ask me if it is that bad or not ... I don't know. There are so many things I don't know." No explanation needed - the people accepted Yevon unconditionally. Even so, these are only small doubts she has, and Yuna continues to demonstrate her faith for Yevon.

Even as a follower of Yevon, Yuna does not really have anything against machina. After all, she is half Al Bhed. Prior to Operation Mi'ihen, she tries to calm Wakka down, saying that even though they're going against the teaching by using machina to defeat Sin, "they're willing to risk it for the greater good." Wakka is steadfast in his belief in Yevon, and Yuna's words do not faze him.

It is only when Yuna stumbles across the Guado Jyscal's sphere that her faith is truly shaken. She finds the truth about Maester Seymour: how he killed his own father for his own wicked ambitions. She tries to stop him, confused by the corruption of the maesters, and ultimately, the party ends up on trial in Bevelle, branded as traitors to Yevon. There, they find out that Sin can never be truly defeated, and Spira is caught in an eternal spiral of death. "Yevon is embodied by eternal, unchanging continuity." Essentially told that the sacrifices of past and future summoners were futile and pointless, Yuna doesn't know what to believe. Such a central part of her life was ripped to shreds.

Yevon betrays her, and yet Yuna decides to continue with her pilgrimage. She doesn't do it to uphold Yevon's ways, but to help the people. Upon reaching Zanarkand and learning the truth behind the Final Summoning, Yuna is appalled. Not only were the teachings of Yevon unsound, the Final Summoning was merely a way to put off Sin's destruction. Yevon stop progress in its tracks. Yuna does not fear Yevon - she has accepted its faults, and is determined to defeat Sin and bring truth to Spira.

I would have gladly died. I live for the people of Spira, and would have gladly died for them. But no more! The Final Summoning ... is a false tradition that should be thrown away.

After defeating Yunalesca, the party finds a way to defeat Sin without the Final Summoning - by killing all of the aeons, and then killing Yu Yevon. With the beginning of the Eternal Calm, Yuna frees Spira from Yevon's stronghold, and the world can finally move forward.

Yuna comes to terms with the falsities behind Yevon. In this, she is able to truly hope for a brighter future, instead of being resigned to one fate.