I wonder what pairing fans would call Tidus and Yuna. Tuna? Yunus? Somebody get back to me on that one. I was a huge fan of the Squall and Rinoa romance in Final Fantasy VIII, and I honestly didn't think I would fall for another paring the same way in the series. Man, I was wrong.
Tidus and Yuna's relationship is perfect to me for the mere fact that they truly complete each other: Their relationship is just a tad rushed though, but Final Fantasy X is a plot-filled video game, and things like that just need to be overlooked.
Let me start at the beginning. A lot of gamers would argue that Tidus was attracted to Yuna, picked her out, had a rage of jealousy, and made her his. It's an interesting concept, but I really don't think Tidus was looking to fall for Yuna from the beginning. When he came to Spira Tidus was struggling inside emotionally. He was confused by the events happening in his life, he didn't feel like he fit in to the party that was forming, and he felt incredibly lonely. As a guy who has experienced a lot of those same feelings at a time, I'll tell you that intentionally establishing a romance is the last thing on your mind. Having feelings like that lowers your self-confidence, and without self-confidence, heck... Try this: don't do your hair, put on your makeup, or whatever you do to yourself in the morning, and go hit on someone you have a crush on. Multiply the feelings you have before doing it by 100 and you have Tidus.
I'm not going to deny the fact that Tidus did crush on Yuna from the beginning. Just look at his face when she's sending near the beginning of the game. He's got the hots for her; it's obvious. I just don't think he intended to fall for her.
Yuna completed him, though, like I said. She took away those feelings of loneliness and confusion, and gave him something to live for. She made him smile, she made him laugh, and eventually she helped him come to terms with his childhood issues. Finding purpose in his life, Tidus became her guardian.
Now let's look at Yuna. I don't think Yuna exactly chose to fall for Tidus, either. In fact, I think it's safe to say she was kind of crushing on Seymour. Her admiration for him was obvious, at any rate, and I personally think she was attracted to him. Granted, Seymour was using Yuna for his own selfish plans, and Yuna eventually realizes this, but is kidnapped and forced to marry him.
There's one component Seymour wasn't calculating in to his plan: Tidus. With an understandable anger at the turn of events, Tidus decides to crash the wedding, and in the process almost gets himself killed. It's then that I believe Yuna started to see that there might be something between her and Tidus. She threatens to kill herself if her friends are harmed, and long story short she falls backward over an edge, presumably to her death. Not really. Luckily she's a summoner, right? Tidus runs over to the edge and yells out "Yuna!" with fear in his eyes.
Yeah, those two had it bad.
Like Yuna completed Tidus, at this point of the game it became apparent that the same was true the other way around, too. They basically switched places. Yuna cries to Tidus more than once, and he is continuously there to comfort and support her. Yuna needed Tidus, and that's what makes the rest of the game so sad.
Because their relationship became tragic. After falling in love with him Yuna had to be the one to let him go.