1. Tidus comes back and it's like he never left. He and Yuna pick up where they left off at the Macalania Spring and he joins the Gullwings so they never have to be apart. They're married within a year, their first child born within two, and only occasionally do they wonder if they rushed into things too quickly.
2. Tidus comes back and he and Yuna attempt to pick up where they left off, but it's just not the same. The intense feelings brought on by the pilgrimage don't survive the mundanity of everyday life on Besaid, and after only two months they realize that they don't love each other and probably never did. After some intense conversation and contemplation, Yuna decides that she'd rather have happy memories of Tidus than an unhappy relationship with him and leaves, returning to the Gullwings. As he watches her board the ship, Tidus smiles sadly, then fades away without a sound.
3. Tidus comes back and Yuna welcomes him with open arms, but she's not quite ready to dismiss the possibility that he might disappear on her again. After a reunion that is as tearful as it is joyful, she becomes clingy and dependent, and eventually Tidus feels smothered and pulls away. He takes off for a little while, spending some time traveling around Spira, then comes back to her. Heartened that he didn't fade while he was gone, Yuna returns to her new, more confident self, and she and Tidus begin again, on more equal footing this time.
4. Tidus comes back to find a Yuna much stronger and more confident than the one he left. After a few weeks of perfect bliss, the cracks begin to show when she wants to continue sphere hunting rather than follow him to Luca to support his blitzball career. Fights and tension follow, and after one particularly loud and tearful night Yuna storms out and sets up house on the Celsius. They stay separated for about a month, after which time they realize that they miss each other desperately and take another shot at a relationship, only more slowly this time, taking the time to really get to know one another. Two years later, Yuna is ready to retire from sphere hunting and take a place in Spira's government, now headquartered in Luca. They move in together; he blitzes, she governs, and they live happily ever after.
5. When Yuna meets the fayth after the defeat of Vegnagun, she chooses the "thank you and goodbye" option, bidding Tidus a bittersweet farewell and finally committing to a life without him. It is a good life, long and happy and filled with friends, lovers, and beautiful, accomplished grandchildren. She thinks of Tidus, occasionally and with great fondness, as the one that could have been, but she is content with her choice and never regrets it.