Yuna is the female protagonist of Final Fantasy X and Final Fantasy X-2. She is the daughter of High Summoner Braska and an unnamed Al Bhed woman, who died when Sin attacked her ship at sea. The Al Bhed woman was the sister of Cid, who is the father of Rikku and Brother, meaning that they are Yuna's cousins. A unique trait of Yuna is her heterochromia, her eyes being two different colors. Her left eye is blue, while the right is a shade of green similar to the Al Bhed, though without the characteristic spiral, showing her half-Al Bhed heritage.
Yuna undergoes some radical changes in character and behavior over the course of the games, but at her core she is a very kind-hearted, loyal, honest and polite young woman who strives to see the best in others and has a very strong conviction to complete whatever task she feels is her duty to perform. As a summoner, she is thankful for her guardians' help.
At the beginning of the game she was a firm follower of Yevon's teachings and often came across as quite naive, believing that her duty to Spira's people and responsibility as a summoner was to defeat Sin. Described by Auron as serious to a fault, she would often hide her own feelings of fear, sadness, and desperation while encouraging others to express themselves in her place. She often seemed quite willing to carry others' burdens to ease their own pain, and was willing to sacrifice her own life to destroy Sin and give up chances for her own happiness if it meant it could help others. However, her contact with - and ever growing love for - Tidus caused her to begin questioning some of Yevon's teachings and became increasingly more direct and open.
When she learned of the hypocrisy in Yevon's upper levels, her Yevonite faith was profoundly shaken, but she resolved to continue her pilgrimage despite Tidus and Rikku's protests. When finally confronted with the truth of the Final Summoning and the "spiral of death" the summoner's pilgrimage ensured, her trust in Yevon was finally shattered. She refused to sacrifice one of her guardians to Yunalesca, and resolved to destroy Sin permanently without the "false hope" of the Final Aeon. After the painful sacrifice of her Aeons to destroy Yu Yevon and bring about an Eternal Calm, she was deeply saddened by Tidus' departure, and proclaimed her love for him before he disappeared (in the Japanese original, she thanked him instead, which was still an indirect response of love).
In the sequel, Yuna had undergone a complete makeover with a more revealing dress style and a new lease of life, being now freed from her former responsibilities as a summoner. Though still unflinchingly polite, soft spoken and driven, she was more worldly-wise, quite playful, and had learned to think and desire for herself. During her time with the Gullwings, Rikku served as a sort-of role model for her, as Yuna displays some of Rikku's eccentric behaviors and even uses some of Rikku's expressions, such as "Disasteriffic" and "Oh, poopie!"; in fact, when she says the latter when Leblanc breaks into their airship, Rikku orders her not to talk like that, and Yuna objects, "I'm just copying you!" Though her friends would occasionally tease her as a pushover due to her inability to refuse a call for help, she could be quite stern and even intimidating if actually angered. She had also developed a strong dislike of sacrifice in the name of victory, a trait Tidus had instilled in her as well as her habit to help people seeing it was "the right thing to do". Her love for Tidus served as her primary motivation, and following the game's conclusion she was happily reunited with him.