** Spoiler Alert!!! click to hide or show**
TIDUS:

Fact:
Tidus is not actually real. He and the Zanarkand he hail's from, are merely dreams of the Fayth, ordered into existence after the destruction of the real Zanarkand with the formation of Sin. The Fayth want Tidus to defeat Sin permanently, so that they can finally rest. Unfortunately, if he complies, the dream will end and Tidus himself will disappear. However, all is not lost, it is said by Bahamut's Fayth: "You have been touched by Sin... you're more than just dreams now." Hence at the end of the game or movie of FFX because Tidus is a fayth he must suffer the same fate as he disappears at the end.
SHUYIN:
Shuyin’s spirit existed for a thousand more years, filled with grief and despair, a shadow of his former self. He dwelt within a small cavern beneath the Mushroom Rock Road called the Den of Woe, where his body was believed to have been buried. The cave was filled with Pyreflies that constantly replayed his memories again and again, a constant reminder to him of Lenne, the love he had lost.
When the Fayth dreamt up the dream Zanarkand, Tidus was made from their memory of Shuyin, making Shuyin and Tidus one and the same.
LONG STORY SHORT SHUYIN IS A GHOST AND TIDUS IS A FAYTH (SAME THING!)