What part plays Yuna in the whole Shuyin/Lenne story? As Yuna says: “It all began when I saw this sphere of you”. The “you” Yuna is talking about refers to her lover, Tidus, but in fact the man she sees in the sphere is Shuyin. After seeing the sphere (you have to remember that when Final Fantasy X ended Tidus was considered more or less dead), an enthusiast Yuna begins looking for him with the help of Rikku and Paine.

Yuna’s second role is being (partially) Lenne. Or, better said, being a mean through which Lenne can speak. Lenne’s thoughts are linked to her Songstress dressphere and when Yuna, one thousand years after Lenne’s death, uses it Lenne’s thoughts and behaviour sometimes influence Yuna’s.

I think Yuna final and most important role is of acting as a medium. In Final Fantasy X one of her tasks as a Summoner was to perform the sending, a dance which helped lost pyreflies to reach the Farplane. Although in Final Fantasy X-2 Yuna doesn’t truly “send” Shuyin (even though he is an Unsent) she certainly played an important part in the reunion between him and Lenne.

As horror stories taught us, ghosts are the souls of people who have unfinished business on Earth, things they have to do before being able to rest in peace. Shuyin can be considered a ghost: after being separated from Lenne he began his relentless quest for her and only when they met, they were able to leave Spira together. It is thanks to Yuna that Shuyin’s search ended: after defeating him, Lenne was able to leave the Songstress Dressphere, talk to Shuyin and finally able to fade away with him.